Collections.java revision 64a91fed2c53ffbf6ee551b3444bfbceb7887b8f
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27package java.util; 28import java.io.Serializable; 29import java.io.ObjectOutputStream; 30import java.io.IOException; 31import java.io.ObjectOutputStream; 32import java.io.Serializable; 33import java.lang.reflect.Array; 34import java.util.function.BiConsumer; 35import java.util.function.BiFunction; 36import java.util.function.Consumer; 37import java.util.function.Function; 38import java.util.function.Predicate; 39import java.util.function.UnaryOperator; 40import java.util.stream.IntStream; 41import java.util.stream.Stream; 42import java.util.stream.StreamSupport; 43 44import dalvik.system.VMRuntime; 45 46/** 47 * This class consists exclusively of static methods that operate on or return 48 * collections. It contains polymorphic algorithms that operate on 49 * collections, "wrappers", which return a new collection backed by a 50 * specified collection, and a few other odds and ends. 51 * 52 * <p>The methods of this class all throw a <tt>NullPointerException</tt> 53 * if the collections or class objects provided to them are null. 54 * 55 * <p>The documentation for the polymorphic algorithms contained in this class 56 * generally includes a brief description of the <i>implementation</i>. Such 57 * descriptions should be regarded as <i>implementation notes</i>, rather than 58 * parts of the <i>specification</i>. Implementors should feel free to 59 * substitute other algorithms, so long as the specification itself is adhered 60 * to. (For example, the algorithm used by <tt>sort</tt> does not have to be 61 * a mergesort, but it does have to be <i>stable</i>.) 62 * 63 * <p>The "destructive" algorithms contained in this class, that is, the 64 * algorithms that modify the collection on which they operate, are specified 65 * to throw <tt>UnsupportedOperationException</tt> if the collection does not 66 * support the appropriate mutation primitive(s), such as the <tt>set</tt> 67 * method. These algorithms may, but are not required to, throw this 68 * exception if an invocation would have no effect on the collection. For 69 * example, invoking the <tt>sort</tt> method on an unmodifiable list that is 70 * already sorted may or may not throw <tt>UnsupportedOperationException</tt>. 71 * 72 * <p>This class is a member of the 73 * <a href="{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/collections/index.html"> 74 * Java Collections Framework</a>. 75 * 76 * @author Josh Bloch 77 * @author Neal Gafter 78 * @see Collection 79 * @see Set 80 * @see List 81 * @see Map 82 * @since 1.2 83 */ 84 85public class Collections { 86 // Suppresses default constructor, ensuring non-instantiability. 87 private Collections() { 88 } 89 90 // Algorithms 91 92 /* 93 * Tuning parameters for algorithms - Many of the List algorithms have 94 * two implementations, one of which is appropriate for RandomAccess 95 * lists, the other for "sequential." Often, the random access variant 96 * yields better performance on small sequential access lists. The 97 * tuning parameters below determine the cutoff point for what constitutes 98 * a "small" sequential access list for each algorithm. The values below 99 * were empirically determined to work well for LinkedList. Hopefully 100 * they should be reasonable for other sequential access List 101 * implementations. Those doing performance work on this code would 102 * do well to validate the values of these parameters from time to time. 103 * (The first word of each tuning parameter name is the algorithm to which 104 * it applies.) 105 */ 106 private static final int BINARYSEARCH_THRESHOLD = 5000; 107 private static final int REVERSE_THRESHOLD = 18; 108 private static final int SHUFFLE_THRESHOLD = 5; 109 private static final int FILL_THRESHOLD = 25; 110 private static final int ROTATE_THRESHOLD = 100; 111 private static final int COPY_THRESHOLD = 10; 112 private static final int REPLACEALL_THRESHOLD = 11; 113 private static final int INDEXOFSUBLIST_THRESHOLD = 35; 114 115 // Android-changed: Warn about Collections.sort() being built on top 116 // of List.sort() when it used to be the other way round in Nougat. 117 /** 118 * Sorts the specified list into ascending order, according to the 119 * {@linkplain Comparable natural ordering} of its elements. 120 * All elements in the list must implement the {@link Comparable} 121 * interface. Furthermore, all elements in the list must be 122 * <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)} 123 * must not throw a {@code ClassCastException} for any elements 124 * {@code e1} and {@code e2} in the list). 125 * 126 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will 127 * not be reordered as a result of the sort. 128 * 129 * <p>The specified list must be modifiable, but need not be resizable. 130 * 131 * @implNote 132 * This implementation defers to the {@link List#sort(Comparator)} 133 * method using the specified list and a {@code null} comparator. 134 * Do not call this method from {@code List.sort()} since that can lead 135 * to infinite recursion. Apps targeting APIs {@code <= 25} observe 136 * backwards compatibility behavior where this method was implemented 137 * on top of {@link List#toArray()}, {@link ListIterator#next()} and 138 * {@link ListIterator#set(Object)}. 139 * 140 * @param <T> the class of the objects in the list 141 * @param list the list to be sorted. 142 * @throws ClassCastException if the list contains elements that are not 143 * <i>mutually comparable</i> (for example, strings and integers). 144 * @throws UnsupportedOperationException if the specified list's 145 * list-iterator does not support the {@code set} operation. 146 * @throws IllegalArgumentException (optional) if the implementation 147 * detects that the natural ordering of the list elements is 148 * found to violate the {@link Comparable} contract 149 * @see List#sort(Comparator) 150 */ 151 @SuppressWarnings("unchecked") 152 public static <T extends Comparable<? super T>> void sort(List<T> list) { 153 // Android-changed: Call sort(list, null) here to be consistent 154 // with that method's (Android-changed) behavior. 155 sort(list, null); 156 // list.sort(null); 157 } 158 159 // Android-changed: Warn about Collections.sort() being built on top 160 // of List.sort() when it used to be the other way round in Nougat. 161 /** 162 * Sorts the specified list according to the order induced by the 163 * specified comparator. All elements in the list must be <i>mutually 164 * comparable</i> using the specified comparator (that is, 165 * {@code c.compare(e1, e2)} must not throw a {@code ClassCastException} 166 * for any elements {@code e1} and {@code e2} in the list). 167 * 168 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will 169 * not be reordered as a result of the sort. 170 * 171 * <p>The specified list must be modifiable, but need not be resizable. 172 * 173 * @implNote 174 * This implementation defers to the {@link List#sort(Comparator)} 175 * method using the specified list and comparator. 176 * Do not call this method from {@code List.sort()} since that can lead 177 * to infinite recursion. Apps targeting APIs {@code <= 25} observe 178 * backwards compatibility behavior where this method was implemented 179 * on top of {@link List#toArray()}, {@link ListIterator#next()} and 180 * {@link ListIterator#set(Object)}. 181 * 182 * @param <T> the class of the objects in the list 183 * @param list the list to be sorted. 184 * @param c the comparator to determine the order of the list. A 185 * {@code null} value indicates that the elements' <i>natural 186 * ordering</i> should be used. 187 * @throws ClassCastException if the list contains elements that are not 188 * <i>mutually comparable</i> using the specified comparator. 189 * @throws UnsupportedOperationException if the specified list's 190 * list-iterator does not support the {@code set} operation. 191 * @throws IllegalArgumentException (optional) if the comparator is 192 * found to violate the {@link Comparator} contract 193 * @see List#sort(Comparator) 194 */ 195 @SuppressWarnings({"unchecked", "rawtypes"}) 196 public static <T> void sort(List<T> list, Comparator<? super T> c) { 197 // Android-changed: Introduced compatibility behavior for apps 198 // targeting API levels <= 25. 199 int targetSdkVersion = VMRuntime.getRuntime().getTargetSdkVersion(); 200 if (targetSdkVersion > 25) { 201 list.sort(c); 202 } else { 203 // Compatibility behavior for API <= 25. http://b/33482884 204 if (list.getClass() == ArrayList.class) { 205 Arrays.sort((T[]) ((ArrayList) list).elementData, 0, list.size(), c); 206 return; 207 } 208 209 Object[] a = list.toArray(); 210 Arrays.sort(a, (Comparator) c); 211 ListIterator<T> i = list.listIterator(); 212 for (int j = 0; j < a.length; j++) { 213 i.next(); 214 i.set((T) a[j]); 215 } 216 } 217 } 218 219 220 /** 221 * Searches the specified list for the specified object using the binary 222 * search algorithm. The list must be sorted into ascending order 223 * according to the {@linkplain Comparable natural ordering} of its 224 * elements (as by the {@link #sort(List)} method) prior to making this 225 * call. If it is not sorted, the results are undefined. If the list 226 * contains multiple elements equal to the specified object, there is no 227 * guarantee which one will be found. 228 * 229 * <p>This method runs in log(n) time for a "random access" list (which 230 * provides near-constant-time positional access). If the specified list 231 * does not implement the {@link RandomAccess} interface and is large, 232 * this method will do an iterator-based binary search that performs 233 * O(n) link traversals and O(log n) element comparisons. 234 * 235 * @param <T> the class of the objects in the list 236 * @param list the list to be searched. 237 * @param key the key to be searched for. 238 * @return the index of the search key, if it is contained in the list; 239 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The 240 * <i>insertion point</i> is defined as the point at which the 241 * key would be inserted into the list: the index of the first 242 * element greater than the key, or <tt>list.size()</tt> if all 243 * elements in the list are less than the specified key. Note 244 * that this guarantees that the return value will be >= 0 if 245 * and only if the key is found. 246 * @throws ClassCastException if the list contains elements that are not 247 * <i>mutually comparable</i> (for example, strings and 248 * integers), or the search key is not mutually comparable 249 * with the elements of the list. 250 */ 251 public static <T> 252 int binarySearch(List<? extends Comparable<? super T>> list, T key) { 253 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) 254 return Collections.indexedBinarySearch(list, key); 255 else 256 return Collections.iteratorBinarySearch(list, key); 257 } 258 259 private static <T> 260 int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) { 261 int low = 0; 262 int high = list.size()-1; 263 264 while (low <= high) { 265 int mid = (low + high) >>> 1; 266 Comparable<? super T> midVal = list.get(mid); 267 int cmp = midVal.compareTo(key); 268 269 if (cmp < 0) 270 low = mid + 1; 271 else if (cmp > 0) 272 high = mid - 1; 273 else 274 return mid; // key found 275 } 276 return -(low + 1); // key not found 277 } 278 279 private static <T> 280 int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key) 281 { 282 int low = 0; 283 int high = list.size()-1; 284 ListIterator<? extends Comparable<? super T>> i = list.listIterator(); 285 286 while (low <= high) { 287 int mid = (low + high) >>> 1; 288 Comparable<? super T> midVal = get(i, mid); 289 int cmp = midVal.compareTo(key); 290 291 if (cmp < 0) 292 low = mid + 1; 293 else if (cmp > 0) 294 high = mid - 1; 295 else 296 return mid; // key found 297 } 298 return -(low + 1); // key not found 299 } 300 301 /** 302 * Gets the ith element from the given list by repositioning the specified 303 * list listIterator. 304 */ 305 private static <T> T get(ListIterator<? extends T> i, int index) { 306 T obj = null; 307 int pos = i.nextIndex(); 308 if (pos <= index) { 309 do { 310 obj = i.next(); 311 } while (pos++ < index); 312 } else { 313 do { 314 obj = i.previous(); 315 } while (--pos > index); 316 } 317 return obj; 318 } 319 320 /** 321 * Searches the specified list for the specified object using the binary 322 * search algorithm. The list must be sorted into ascending order 323 * according to the specified comparator (as by the 324 * {@link #sort(List, Comparator) sort(List, Comparator)} 325 * method), prior to making this call. If it is 326 * not sorted, the results are undefined. If the list contains multiple 327 * elements equal to the specified object, there is no guarantee which one 328 * will be found. 329 * 330 * <p>This method runs in log(n) time for a "random access" list (which 331 * provides near-constant-time positional access). If the specified list 332 * does not implement the {@link RandomAccess} interface and is large, 333 * this method will do an iterator-based binary search that performs 334 * O(n) link traversals and O(log n) element comparisons. 335 * 336 * @param <T> the class of the objects in the list 337 * @param list the list to be searched. 338 * @param key the key to be searched for. 339 * @param c the comparator by which the list is ordered. 340 * A <tt>null</tt> value indicates that the elements' 341 * {@linkplain Comparable natural ordering} should be used. 342 * @return the index of the search key, if it is contained in the list; 343 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The 344 * <i>insertion point</i> is defined as the point at which the 345 * key would be inserted into the list: the index of the first 346 * element greater than the key, or <tt>list.size()</tt> if all 347 * elements in the list are less than the specified key. Note 348 * that this guarantees that the return value will be >= 0 if 349 * and only if the key is found. 350 * @throws ClassCastException if the list contains elements that are not 351 * <i>mutually comparable</i> using the specified comparator, 352 * or the search key is not mutually comparable with the 353 * elements of the list using this comparator. 354 */ 355 @SuppressWarnings("unchecked") 356 public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) { 357 if (c==null) 358 return binarySearch((List<? extends Comparable<? super T>>) list, key); 359 360 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) 361 return Collections.indexedBinarySearch(list, key, c); 362 else 363 return Collections.iteratorBinarySearch(list, key, c); 364 } 365 366 private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { 367 int low = 0; 368 int high = l.size()-1; 369 370 while (low <= high) { 371 int mid = (low + high) >>> 1; 372 T midVal = l.get(mid); 373 int cmp = c.compare(midVal, key); 374 375 if (cmp < 0) 376 low = mid + 1; 377 else if (cmp > 0) 378 high = mid - 1; 379 else 380 return mid; // key found 381 } 382 return -(low + 1); // key not found 383 } 384 385 private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { 386 int low = 0; 387 int high = l.size()-1; 388 ListIterator<? extends T> i = l.listIterator(); 389 390 while (low <= high) { 391 int mid = (low + high) >>> 1; 392 T midVal = get(i, mid); 393 int cmp = c.compare(midVal, key); 394 395 if (cmp < 0) 396 low = mid + 1; 397 else if (cmp > 0) 398 high = mid - 1; 399 else 400 return mid; // key found 401 } 402 return -(low + 1); // key not found 403 } 404 405 /** 406 * Reverses the order of the elements in the specified list.<p> 407 * 408 * This method runs in linear time. 409 * 410 * @param list the list whose elements are to be reversed. 411 * @throws UnsupportedOperationException if the specified list or 412 * its list-iterator does not support the <tt>set</tt> operation. 413 */ 414 @SuppressWarnings({"rawtypes", "unchecked"}) 415 public static void reverse(List<?> list) { 416 int size = list.size(); 417 if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) { 418 for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--) 419 swap(list, i, j); 420 } else { 421 // instead of using a raw type here, it's possible to capture 422 // the wildcard but it will require a call to a supplementary 423 // private method 424 ListIterator fwd = list.listIterator(); 425 ListIterator rev = list.listIterator(size); 426 for (int i=0, mid=list.size()>>1; i<mid; i++) { 427 Object tmp = fwd.next(); 428 fwd.set(rev.previous()); 429 rev.set(tmp); 430 } 431 } 432 } 433 434 /** 435 * Randomly permutes the specified list using a default source of 436 * randomness. All permutations occur with approximately equal 437 * likelihood. 438 * 439 * <p>The hedge "approximately" is used in the foregoing description because 440 * default source of randomness is only approximately an unbiased source 441 * of independently chosen bits. If it were a perfect source of randomly 442 * chosen bits, then the algorithm would choose permutations with perfect 443 * uniformity. 444 * 445 * <p>This implementation traverses the list backwards, from the last 446 * element up to the second, repeatedly swapping a randomly selected element 447 * into the "current position". Elements are randomly selected from the 448 * portion of the list that runs from the first element to the current 449 * position, inclusive. 450 * 451 * <p>This method runs in linear time. If the specified list does not 452 * implement the {@link RandomAccess} interface and is large, this 453 * implementation dumps the specified list into an array before shuffling 454 * it, and dumps the shuffled array back into the list. This avoids the 455 * quadratic behavior that would result from shuffling a "sequential 456 * access" list in place. 457 * 458 * @param list the list to be shuffled. 459 * @throws UnsupportedOperationException if the specified list or 460 * its list-iterator does not support the <tt>set</tt> operation. 461 */ 462 public static void shuffle(List<?> list) { 463 Random rnd = r; 464 if (rnd == null) 465 r = rnd = new Random(); // harmless race. 466 shuffle(list, rnd); 467 } 468 469 private static Random r; 470 471 /** 472 * Randomly permute the specified list using the specified source of 473 * randomness. All permutations occur with equal likelihood 474 * assuming that the source of randomness is fair.<p> 475 * 476 * This implementation traverses the list backwards, from the last element 477 * up to the second, repeatedly swapping a randomly selected element into 478 * the "current position". Elements are randomly selected from the 479 * portion of the list that runs from the first element to the current 480 * position, inclusive.<p> 481 * 482 * This method runs in linear time. If the specified list does not 483 * implement the {@link RandomAccess} interface and is large, this 484 * implementation dumps the specified list into an array before shuffling 485 * it, and dumps the shuffled array back into the list. This avoids the 486 * quadratic behavior that would result from shuffling a "sequential 487 * access" list in place. 488 * 489 * @param list the list to be shuffled. 490 * @param rnd the source of randomness to use to shuffle the list. 491 * @throws UnsupportedOperationException if the specified list or its 492 * list-iterator does not support the <tt>set</tt> operation. 493 */ 494 @SuppressWarnings({"rawtypes", "unchecked"}) 495 public static void shuffle(List<?> list, Random rnd) { 496 int size = list.size(); 497 if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) { 498 for (int i=size; i>1; i--) 499 swap(list, i-1, rnd.nextInt(i)); 500 } else { 501 Object arr[] = list.toArray(); 502 503 // Shuffle array 504 for (int i=size; i>1; i--) 505 swap(arr, i-1, rnd.nextInt(i)); 506 507 // Dump array back into list 508 // instead of using a raw type here, it's possible to capture 509 // the wildcard but it will require a call to a supplementary 510 // private method 511 ListIterator it = list.listIterator(); 512 for (int i=0; i<arr.length; i++) { 513 it.next(); 514 it.set(arr[i]); 515 } 516 } 517 } 518 519 /** 520 * Swaps the elements at the specified positions in the specified list. 521 * (If the specified positions are equal, invoking this method leaves 522 * the list unchanged.) 523 * 524 * @param list The list in which to swap elements. 525 * @param i the index of one element to be swapped. 526 * @param j the index of the other element to be swapped. 527 * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt> 528 * is out of range (i < 0 || i >= list.size() 529 * || j < 0 || j >= list.size()). 530 * @since 1.4 531 */ 532 @SuppressWarnings({"rawtypes", "unchecked"}) 533 public static void swap(List<?> list, int i, int j) { 534 // instead of using a raw type here, it's possible to capture 535 // the wildcard but it will require a call to a supplementary 536 // private method 537 final List l = list; 538 l.set(i, l.set(j, l.get(i))); 539 } 540 541 /** 542 * Swaps the two specified elements in the specified array. 543 */ 544 private static void swap(Object[] arr, int i, int j) { 545 Object tmp = arr[i]; 546 arr[i] = arr[j]; 547 arr[j] = tmp; 548 } 549 550 /** 551 * Replaces all of the elements of the specified list with the specified 552 * element. <p> 553 * 554 * This method runs in linear time. 555 * 556 * @param <T> the class of the objects in the list 557 * @param list the list to be filled with the specified element. 558 * @param obj The element with which to fill the specified list. 559 * @throws UnsupportedOperationException if the specified list or its 560 * list-iterator does not support the <tt>set</tt> operation. 561 */ 562 public static <T> void fill(List<? super T> list, T obj) { 563 int size = list.size(); 564 565 if (size < FILL_THRESHOLD || list instanceof RandomAccess) { 566 for (int i=0; i<size; i++) 567 list.set(i, obj); 568 } else { 569 ListIterator<? super T> itr = list.listIterator(); 570 for (int i=0; i<size; i++) { 571 itr.next(); 572 itr.set(obj); 573 } 574 } 575 } 576 577 /** 578 * Copies all of the elements from one list into another. After the 579 * operation, the index of each copied element in the destination list 580 * will be identical to its index in the source list. The destination 581 * list must be at least as long as the source list. If it is longer, the 582 * remaining elements in the destination list are unaffected. <p> 583 * 584 * This method runs in linear time. 585 * 586 * @param <T> the class of the objects in the lists 587 * @param dest The destination list. 588 * @param src The source list. 589 * @throws IndexOutOfBoundsException if the destination list is too small 590 * to contain the entire source List. 591 * @throws UnsupportedOperationException if the destination list's 592 * list-iterator does not support the <tt>set</tt> operation. 593 */ 594 public static <T> void copy(List<? super T> dest, List<? extends T> src) { 595 int srcSize = src.size(); 596 if (srcSize > dest.size()) 597 throw new IndexOutOfBoundsException("Source does not fit in dest"); 598 599 if (srcSize < COPY_THRESHOLD || 600 (src instanceof RandomAccess && dest instanceof RandomAccess)) { 601 for (int i=0; i<srcSize; i++) 602 dest.set(i, src.get(i)); 603 } else { 604 ListIterator<? super T> di=dest.listIterator(); 605 ListIterator<? extends T> si=src.listIterator(); 606 for (int i=0; i<srcSize; i++) { 607 di.next(); 608 di.set(si.next()); 609 } 610 } 611 } 612 613 /** 614 * Returns the minimum element of the given collection, according to the 615 * <i>natural ordering</i> of its elements. All elements in the 616 * collection must implement the <tt>Comparable</tt> interface. 617 * Furthermore, all elements in the collection must be <i>mutually 618 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a 619 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 620 * <tt>e2</tt> in the collection).<p> 621 * 622 * This method iterates over the entire collection, hence it requires 623 * time proportional to the size of the collection. 624 * 625 * @param <T> the class of the objects in the collection 626 * @param coll the collection whose minimum element is to be determined. 627 * @return the minimum element of the given collection, according 628 * to the <i>natural ordering</i> of its elements. 629 * @throws ClassCastException if the collection contains elements that are 630 * not <i>mutually comparable</i> (for example, strings and 631 * integers). 632 * @throws NoSuchElementException if the collection is empty. 633 * @see Comparable 634 */ 635 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) { 636 Iterator<? extends T> i = coll.iterator(); 637 T candidate = i.next(); 638 639 while (i.hasNext()) { 640 T next = i.next(); 641 if (next.compareTo(candidate) < 0) 642 candidate = next; 643 } 644 return candidate; 645 } 646 647 /** 648 * Returns the minimum element of the given collection, according to the 649 * order induced by the specified comparator. All elements in the 650 * collection must be <i>mutually comparable</i> by the specified 651 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a 652 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 653 * <tt>e2</tt> in the collection).<p> 654 * 655 * This method iterates over the entire collection, hence it requires 656 * time proportional to the size of the collection. 657 * 658 * @param <T> the class of the objects in the collection 659 * @param coll the collection whose minimum element is to be determined. 660 * @param comp the comparator with which to determine the minimum element. 661 * A <tt>null</tt> value indicates that the elements' <i>natural 662 * ordering</i> should be used. 663 * @return the minimum element of the given collection, according 664 * to the specified comparator. 665 * @throws ClassCastException if the collection contains elements that are 666 * not <i>mutually comparable</i> using the specified comparator. 667 * @throws NoSuchElementException if the collection is empty. 668 * @see Comparable 669 */ 670 @SuppressWarnings({"unchecked", "rawtypes"}) 671 public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) { 672 if (comp==null) 673 return (T)min((Collection) coll); 674 675 Iterator<? extends T> i = coll.iterator(); 676 T candidate = i.next(); 677 678 while (i.hasNext()) { 679 T next = i.next(); 680 if (comp.compare(next, candidate) < 0) 681 candidate = next; 682 } 683 return candidate; 684 } 685 686 /** 687 * Returns the maximum element of the given collection, according to the 688 * <i>natural ordering</i> of its elements. All elements in the 689 * collection must implement the <tt>Comparable</tt> interface. 690 * Furthermore, all elements in the collection must be <i>mutually 691 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a 692 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 693 * <tt>e2</tt> in the collection).<p> 694 * 695 * This method iterates over the entire collection, hence it requires 696 * time proportional to the size of the collection. 697 * 698 * @param <T> the class of the objects in the collection 699 * @param coll the collection whose maximum element is to be determined. 700 * @return the maximum element of the given collection, according 701 * to the <i>natural ordering</i> of its elements. 702 * @throws ClassCastException if the collection contains elements that are 703 * not <i>mutually comparable</i> (for example, strings and 704 * integers). 705 * @throws NoSuchElementException if the collection is empty. 706 * @see Comparable 707 */ 708 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) { 709 Iterator<? extends T> i = coll.iterator(); 710 T candidate = i.next(); 711 712 while (i.hasNext()) { 713 T next = i.next(); 714 if (next.compareTo(candidate) > 0) 715 candidate = next; 716 } 717 return candidate; 718 } 719 720 /** 721 * Returns the maximum element of the given collection, according to the 722 * order induced by the specified comparator. All elements in the 723 * collection must be <i>mutually comparable</i> by the specified 724 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a 725 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 726 * <tt>e2</tt> in the collection).<p> 727 * 728 * This method iterates over the entire collection, hence it requires 729 * time proportional to the size of the collection. 730 * 731 * @param <T> the class of the objects in the collection 732 * @param coll the collection whose maximum element is to be determined. 733 * @param comp the comparator with which to determine the maximum element. 734 * A <tt>null</tt> value indicates that the elements' <i>natural 735 * ordering</i> should be used. 736 * @return the maximum element of the given collection, according 737 * to the specified comparator. 738 * @throws ClassCastException if the collection contains elements that are 739 * not <i>mutually comparable</i> using the specified comparator. 740 * @throws NoSuchElementException if the collection is empty. 741 * @see Comparable 742 */ 743 @SuppressWarnings({"unchecked", "rawtypes"}) 744 public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) { 745 if (comp==null) 746 return (T)max((Collection) coll); 747 748 Iterator<? extends T> i = coll.iterator(); 749 T candidate = i.next(); 750 751 while (i.hasNext()) { 752 T next = i.next(); 753 if (comp.compare(next, candidate) > 0) 754 candidate = next; 755 } 756 return candidate; 757 } 758 759 /** 760 * Rotates the elements in the specified list by the specified distance. 761 * After calling this method, the element at index <tt>i</tt> will be 762 * the element previously at index <tt>(i - distance)</tt> mod 763 * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt> 764 * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on 765 * the size of the list.) 766 * 767 * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>. 768 * After invoking <tt>Collections.rotate(list, 1)</tt> (or 769 * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise 770 * <tt>[s, t, a, n, k]</tt>. 771 * 772 * <p>Note that this method can usefully be applied to sublists to 773 * move one or more elements within a list while preserving the 774 * order of the remaining elements. For example, the following idiom 775 * moves the element at index <tt>j</tt> forward to position 776 * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>): 777 * <pre> 778 * Collections.rotate(list.subList(j, k+1), -1); 779 * </pre> 780 * To make this concrete, suppose <tt>list</tt> comprises 781 * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt> 782 * (<tt>b</tt>) forward two positions, perform the following invocation: 783 * <pre> 784 * Collections.rotate(l.subList(1, 4), -1); 785 * </pre> 786 * The resulting list is <tt>[a, c, d, b, e]</tt>. 787 * 788 * <p>To move more than one element forward, increase the absolute value 789 * of the rotation distance. To move elements backward, use a positive 790 * shift distance. 791 * 792 * <p>If the specified list is small or implements the {@link 793 * RandomAccess} interface, this implementation exchanges the first 794 * element into the location it should go, and then repeatedly exchanges 795 * the displaced element into the location it should go until a displaced 796 * element is swapped into the first element. If necessary, the process 797 * is repeated on the second and successive elements, until the rotation 798 * is complete. If the specified list is large and doesn't implement the 799 * <tt>RandomAccess</tt> interface, this implementation breaks the 800 * list into two sublist views around index <tt>-distance mod size</tt>. 801 * Then the {@link #reverse(List)} method is invoked on each sublist view, 802 * and finally it is invoked on the entire list. For a more complete 803 * description of both algorithms, see Section 2.3 of Jon Bentley's 804 * <i>Programming Pearls</i> (Addison-Wesley, 1986). 805 * 806 * @param list the list to be rotated. 807 * @param distance the distance to rotate the list. There are no 808 * constraints on this value; it may be zero, negative, or 809 * greater than <tt>list.size()</tt>. 810 * @throws UnsupportedOperationException if the specified list or 811 * its list-iterator does not support the <tt>set</tt> operation. 812 * @since 1.4 813 */ 814 public static void rotate(List<?> list, int distance) { 815 if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD) 816 rotate1(list, distance); 817 else 818 rotate2(list, distance); 819 } 820 821 private static <T> void rotate1(List<T> list, int distance) { 822 int size = list.size(); 823 if (size == 0) 824 return; 825 distance = distance % size; 826 if (distance < 0) 827 distance += size; 828 if (distance == 0) 829 return; 830 831 for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) { 832 T displaced = list.get(cycleStart); 833 int i = cycleStart; 834 do { 835 i += distance; 836 if (i >= size) 837 i -= size; 838 displaced = list.set(i, displaced); 839 nMoved ++; 840 } while (i != cycleStart); 841 } 842 } 843 844 private static void rotate2(List<?> list, int distance) { 845 int size = list.size(); 846 if (size == 0) 847 return; 848 int mid = -distance % size; 849 if (mid < 0) 850 mid += size; 851 if (mid == 0) 852 return; 853 854 reverse(list.subList(0, mid)); 855 reverse(list.subList(mid, size)); 856 reverse(list); 857 } 858 859 /** 860 * Replaces all occurrences of one specified value in a list with another. 861 * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt> 862 * in <tt>list</tt> such that 863 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. 864 * (This method has no effect on the size of the list.) 865 * 866 * @param <T> the class of the objects in the list 867 * @param list the list in which replacement is to occur. 868 * @param oldVal the old value to be replaced. 869 * @param newVal the new value with which <tt>oldVal</tt> is to be 870 * replaced. 871 * @return <tt>true</tt> if <tt>list</tt> contained one or more elements 872 * <tt>e</tt> such that 873 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. 874 * @throws UnsupportedOperationException if the specified list or 875 * its list-iterator does not support the <tt>set</tt> operation. 876 * @since 1.4 877 */ 878 public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) { 879 boolean result = false; 880 int size = list.size(); 881 if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) { 882 if (oldVal==null) { 883 for (int i=0; i<size; i++) { 884 if (list.get(i)==null) { 885 list.set(i, newVal); 886 result = true; 887 } 888 } 889 } else { 890 for (int i=0; i<size; i++) { 891 if (oldVal.equals(list.get(i))) { 892 list.set(i, newVal); 893 result = true; 894 } 895 } 896 } 897 } else { 898 ListIterator<T> itr=list.listIterator(); 899 if (oldVal==null) { 900 for (int i=0; i<size; i++) { 901 if (itr.next()==null) { 902 itr.set(newVal); 903 result = true; 904 } 905 } 906 } else { 907 for (int i=0; i<size; i++) { 908 if (oldVal.equals(itr.next())) { 909 itr.set(newVal); 910 result = true; 911 } 912 } 913 } 914 } 915 return result; 916 } 917 918 /** 919 * Returns the starting position of the first occurrence of the specified 920 * target list within the specified source list, or -1 if there is no 921 * such occurrence. More formally, returns the lowest index <tt>i</tt> 922 * such that {@code source.subList(i, i+target.size()).equals(target)}, 923 * or -1 if there is no such index. (Returns -1 if 924 * {@code target.size() > source.size()}) 925 * 926 * <p>This implementation uses the "brute force" technique of scanning 927 * over the source list, looking for a match with the target at each 928 * location in turn. 929 * 930 * @param source the list in which to search for the first occurrence 931 * of <tt>target</tt>. 932 * @param target the list to search for as a subList of <tt>source</tt>. 933 * @return the starting position of the first occurrence of the specified 934 * target list within the specified source list, or -1 if there 935 * is no such occurrence. 936 * @since 1.4 937 */ 938 public static int indexOfSubList(List<?> source, List<?> target) { 939 int sourceSize = source.size(); 940 int targetSize = target.size(); 941 int maxCandidate = sourceSize - targetSize; 942 943 if (sourceSize < INDEXOFSUBLIST_THRESHOLD || 944 (source instanceof RandomAccess&&target instanceof RandomAccess)) { 945 nextCand: 946 for (int candidate = 0; candidate <= maxCandidate; candidate++) { 947 for (int i=0, j=candidate; i<targetSize; i++, j++) 948 if (!eq(target.get(i), source.get(j))) 949 continue nextCand; // Element mismatch, try next cand 950 return candidate; // All elements of candidate matched target 951 } 952 } else { // Iterator version of above algorithm 953 ListIterator<?> si = source.listIterator(); 954 nextCand: 955 for (int candidate = 0; candidate <= maxCandidate; candidate++) { 956 ListIterator<?> ti = target.listIterator(); 957 for (int i=0; i<targetSize; i++) { 958 if (!eq(ti.next(), si.next())) { 959 // Back up source iterator to next candidate 960 for (int j=0; j<i; j++) 961 si.previous(); 962 continue nextCand; 963 } 964 } 965 return candidate; 966 } 967 } 968 return -1; // No candidate matched the target 969 } 970 971 /** 972 * Returns the starting position of the last occurrence of the specified 973 * target list within the specified source list, or -1 if there is no such 974 * occurrence. More formally, returns the highest index <tt>i</tt> 975 * such that {@code source.subList(i, i+target.size()).equals(target)}, 976 * or -1 if there is no such index. (Returns -1 if 977 * {@code target.size() > source.size()}) 978 * 979 * <p>This implementation uses the "brute force" technique of iterating 980 * over the source list, looking for a match with the target at each 981 * location in turn. 982 * 983 * @param source the list in which to search for the last occurrence 984 * of <tt>target</tt>. 985 * @param target the list to search for as a subList of <tt>source</tt>. 986 * @return the starting position of the last occurrence of the specified 987 * target list within the specified source list, or -1 if there 988 * is no such occurrence. 989 * @since 1.4 990 */ 991 public static int lastIndexOfSubList(List<?> source, List<?> target) { 992 int sourceSize = source.size(); 993 int targetSize = target.size(); 994 int maxCandidate = sourceSize - targetSize; 995 996 if (sourceSize < INDEXOFSUBLIST_THRESHOLD || 997 source instanceof RandomAccess) { // Index access version 998 nextCand: 999 for (int candidate = maxCandidate; candidate >= 0; candidate--) { 1000 for (int i=0, j=candidate; i<targetSize; i++, j++) 1001 if (!eq(target.get(i), source.get(j))) 1002 continue nextCand; // Element mismatch, try next cand 1003 return candidate; // All elements of candidate matched target 1004 } 1005 } else { // Iterator version of above algorithm 1006 if (maxCandidate < 0) 1007 return -1; 1008 ListIterator<?> si = source.listIterator(maxCandidate); 1009 nextCand: 1010 for (int candidate = maxCandidate; candidate >= 0; candidate--) { 1011 ListIterator<?> ti = target.listIterator(); 1012 for (int i=0; i<targetSize; i++) { 1013 if (!eq(ti.next(), si.next())) { 1014 if (candidate != 0) { 1015 // Back up source iterator to next candidate 1016 for (int j=0; j<=i+1; j++) 1017 si.previous(); 1018 } 1019 continue nextCand; 1020 } 1021 } 1022 return candidate; 1023 } 1024 } 1025 return -1; // No candidate matched the target 1026 } 1027 1028 1029 // Unmodifiable Wrappers 1030 1031 /** 1032 * Returns an unmodifiable view of the specified collection. This method 1033 * allows modules to provide users with "read-only" access to internal 1034 * collections. Query operations on the returned collection "read through" 1035 * to the specified collection, and attempts to modify the returned 1036 * collection, whether direct or via its iterator, result in an 1037 * <tt>UnsupportedOperationException</tt>.<p> 1038 * 1039 * The returned collection does <i>not</i> pass the hashCode and equals 1040 * operations through to the backing collection, but relies on 1041 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This 1042 * is necessary to preserve the contracts of these operations in the case 1043 * that the backing collection is a set or a list.<p> 1044 * 1045 * The returned collection will be serializable if the specified collection 1046 * is serializable. 1047 * 1048 * @param <T> the class of the objects in the collection 1049 * @param c the collection for which an unmodifiable view is to be 1050 * returned. 1051 * @return an unmodifiable view of the specified collection. 1052 */ 1053 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) { 1054 return new UnmodifiableCollection<>(c); 1055 } 1056 1057 /** 1058 * @serial include 1059 */ 1060 static class UnmodifiableCollection<E> implements Collection<E>, Serializable { 1061 private static final long serialVersionUID = 1820017752578914078L; 1062 1063 final Collection<? extends E> c; 1064 1065 UnmodifiableCollection(Collection<? extends E> c) { 1066 if (c==null) 1067 throw new NullPointerException(); 1068 this.c = c; 1069 } 1070 1071 public int size() {return c.size();} 1072 public boolean isEmpty() {return c.isEmpty();} 1073 public boolean contains(Object o) {return c.contains(o);} 1074 public Object[] toArray() {return c.toArray();} 1075 public <T> T[] toArray(T[] a) {return c.toArray(a);} 1076 public String toString() {return c.toString();} 1077 1078 public Iterator<E> iterator() { 1079 return new Iterator<E>() { 1080 private final Iterator<? extends E> i = c.iterator(); 1081 1082 public boolean hasNext() {return i.hasNext();} 1083 public E next() {return i.next();} 1084 public void remove() { 1085 throw new UnsupportedOperationException(); 1086 } 1087 @Override 1088 public void forEachRemaining(Consumer<? super E> action) { 1089 // Use backing collection version 1090 i.forEachRemaining(action); 1091 } 1092 }; 1093 } 1094 1095 public boolean add(E e) { 1096 throw new UnsupportedOperationException(); 1097 } 1098 public boolean remove(Object o) { 1099 throw new UnsupportedOperationException(); 1100 } 1101 1102 public boolean containsAll(Collection<?> coll) { 1103 return c.containsAll(coll); 1104 } 1105 public boolean addAll(Collection<? extends E> coll) { 1106 throw new UnsupportedOperationException(); 1107 } 1108 public boolean removeAll(Collection<?> coll) { 1109 throw new UnsupportedOperationException(); 1110 } 1111 public boolean retainAll(Collection<?> coll) { 1112 throw new UnsupportedOperationException(); 1113 } 1114 public void clear() { 1115 throw new UnsupportedOperationException(); 1116 } 1117 1118 // Override default methods in Collection 1119 @Override 1120 public void forEach(Consumer<? super E> action) { 1121 c.forEach(action); 1122 } 1123 @Override 1124 public boolean removeIf(Predicate<? super E> filter) { 1125 throw new UnsupportedOperationException(); 1126 } 1127 @SuppressWarnings("unchecked") 1128 @Override 1129 public Spliterator<E> spliterator() { 1130 return (Spliterator<E>)c.spliterator(); 1131 } 1132 @SuppressWarnings("unchecked") 1133 @Override 1134 public Stream<E> stream() { 1135 return (Stream<E>)c.stream(); 1136 } 1137 @SuppressWarnings("unchecked") 1138 @Override 1139 public Stream<E> parallelStream() { 1140 return (Stream<E>)c.parallelStream(); 1141 } 1142 } 1143 1144 /** 1145 * Returns an unmodifiable view of the specified set. This method allows 1146 * modules to provide users with "read-only" access to internal sets. 1147 * Query operations on the returned set "read through" to the specified 1148 * set, and attempts to modify the returned set, whether direct or via its 1149 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p> 1150 * 1151 * The returned set will be serializable if the specified set 1152 * is serializable. 1153 * 1154 * @param <T> the class of the objects in the set 1155 * @param s the set for which an unmodifiable view is to be returned. 1156 * @return an unmodifiable view of the specified set. 1157 */ 1158 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) { 1159 return new UnmodifiableSet<>(s); 1160 } 1161 1162 /** 1163 * @serial include 1164 */ 1165 static class UnmodifiableSet<E> extends UnmodifiableCollection<E> 1166 implements Set<E>, Serializable { 1167 private static final long serialVersionUID = -9215047833775013803L; 1168 1169 UnmodifiableSet(Set<? extends E> s) {super(s);} 1170 public boolean equals(Object o) {return o == this || c.equals(o);} 1171 public int hashCode() {return c.hashCode();} 1172 } 1173 1174 /** 1175 * Returns an unmodifiable view of the specified sorted set. This method 1176 * allows modules to provide users with "read-only" access to internal 1177 * sorted sets. Query operations on the returned sorted set "read 1178 * through" to the specified sorted set. Attempts to modify the returned 1179 * sorted set, whether direct, via its iterator, or via its 1180 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in 1181 * an <tt>UnsupportedOperationException</tt>.<p> 1182 * 1183 * The returned sorted set will be serializable if the specified sorted set 1184 * is serializable. 1185 * 1186 * @param <T> the class of the objects in the set 1187 * @param s the sorted set for which an unmodifiable view is to be 1188 * returned. 1189 * @return an unmodifiable view of the specified sorted set. 1190 */ 1191 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) { 1192 return new UnmodifiableSortedSet<>(s); 1193 } 1194 1195 /** 1196 * @serial include 1197 */ 1198 static class UnmodifiableSortedSet<E> 1199 extends UnmodifiableSet<E> 1200 implements SortedSet<E>, Serializable { 1201 private static final long serialVersionUID = -4929149591599911165L; 1202 private final SortedSet<E> ss; 1203 1204 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;} 1205 1206 public Comparator<? super E> comparator() {return ss.comparator();} 1207 1208 public SortedSet<E> subSet(E fromElement, E toElement) { 1209 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement)); 1210 } 1211 public SortedSet<E> headSet(E toElement) { 1212 return new UnmodifiableSortedSet<>(ss.headSet(toElement)); 1213 } 1214 public SortedSet<E> tailSet(E fromElement) { 1215 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement)); 1216 } 1217 1218 public E first() {return ss.first();} 1219 public E last() {return ss.last();} 1220 } 1221 1222 /** 1223 * Returns an unmodifiable view of the specified navigable set. This method 1224 * allows modules to provide users with "read-only" access to internal 1225 * navigable sets. Query operations on the returned navigable set "read 1226 * through" to the specified navigable set. Attempts to modify the returned 1227 * navigable set, whether direct, via its iterator, or via its 1228 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in 1229 * an {@code UnsupportedOperationException}.<p> 1230 * 1231 * The returned navigable set will be serializable if the specified 1232 * navigable set is serializable. 1233 * 1234 * @param <T> the class of the objects in the set 1235 * @param s the navigable set for which an unmodifiable view is to be 1236 * returned 1237 * @return an unmodifiable view of the specified navigable set 1238 * @since 1.8 1239 */ 1240 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) { 1241 return new UnmodifiableNavigableSet<>(s); 1242 } 1243 1244 /** 1245 * Wraps a navigable set and disables all of the mutative operations. 1246 * 1247 * @param <E> type of elements 1248 * @serial include 1249 */ 1250 static class UnmodifiableNavigableSet<E> 1251 extends UnmodifiableSortedSet<E> 1252 implements NavigableSet<E>, Serializable { 1253 1254 private static final long serialVersionUID = -6027448201786391929L; 1255 1256 /** 1257 * A singleton empty unmodifiable navigable set used for 1258 * {@link #emptyNavigableSet()}. 1259 * 1260 * @param <E> type of elements, if there were any, and bounds 1261 */ 1262 private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E> 1263 implements Serializable { 1264 private static final long serialVersionUID = -6291252904449939134L; 1265 1266 public EmptyNavigableSet() { 1267 super(new TreeSet<E>()); 1268 } 1269 1270 private Object readResolve() { return EMPTY_NAVIGABLE_SET; } 1271 } 1272 1273 @SuppressWarnings("rawtypes") 1274 private static final NavigableSet<?> EMPTY_NAVIGABLE_SET = 1275 new EmptyNavigableSet<>(); 1276 1277 /** 1278 * The instance we are protecting. 1279 */ 1280 private final NavigableSet<E> ns; 1281 1282 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;} 1283 1284 public E lower(E e) { return ns.lower(e); } 1285 public E floor(E e) { return ns.floor(e); } 1286 public E ceiling(E e) { return ns.ceiling(e); } 1287 public E higher(E e) { return ns.higher(e); } 1288 public E pollFirst() { throw new UnsupportedOperationException(); } 1289 public E pollLast() { throw new UnsupportedOperationException(); } 1290 public NavigableSet<E> descendingSet() 1291 { return new UnmodifiableNavigableSet<>(ns.descendingSet()); } 1292 public Iterator<E> descendingIterator() 1293 { return descendingSet().iterator(); } 1294 1295 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 1296 return new UnmodifiableNavigableSet<>( 1297 ns.subSet(fromElement, fromInclusive, toElement, toInclusive)); 1298 } 1299 1300 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 1301 return new UnmodifiableNavigableSet<>( 1302 ns.headSet(toElement, inclusive)); 1303 } 1304 1305 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 1306 return new UnmodifiableNavigableSet<>( 1307 ns.tailSet(fromElement, inclusive)); 1308 } 1309 } 1310 1311 /** 1312 * Returns an unmodifiable view of the specified list. This method allows 1313 * modules to provide users with "read-only" access to internal 1314 * lists. Query operations on the returned list "read through" to the 1315 * specified list, and attempts to modify the returned list, whether 1316 * direct or via its iterator, result in an 1317 * <tt>UnsupportedOperationException</tt>.<p> 1318 * 1319 * The returned list will be serializable if the specified list 1320 * is serializable. Similarly, the returned list will implement 1321 * {@link RandomAccess} if the specified list does. 1322 * 1323 * @param <T> the class of the objects in the list 1324 * @param list the list for which an unmodifiable view is to be returned. 1325 * @return an unmodifiable view of the specified list. 1326 */ 1327 public static <T> List<T> unmodifiableList(List<? extends T> list) { 1328 return (list instanceof RandomAccess ? 1329 new UnmodifiableRandomAccessList<>(list) : 1330 new UnmodifiableList<>(list)); 1331 } 1332 1333 /** 1334 * @serial include 1335 */ 1336 static class UnmodifiableList<E> extends UnmodifiableCollection<E> 1337 implements List<E> { 1338 private static final long serialVersionUID = -283967356065247728L; 1339 1340 final List<? extends E> list; 1341 1342 UnmodifiableList(List<? extends E> list) { 1343 super(list); 1344 this.list = list; 1345 } 1346 1347 public boolean equals(Object o) {return o == this || list.equals(o);} 1348 public int hashCode() {return list.hashCode();} 1349 1350 public E get(int index) {return list.get(index);} 1351 public E set(int index, E element) { 1352 throw new UnsupportedOperationException(); 1353 } 1354 public void add(int index, E element) { 1355 throw new UnsupportedOperationException(); 1356 } 1357 public E remove(int index) { 1358 throw new UnsupportedOperationException(); 1359 } 1360 public int indexOf(Object o) {return list.indexOf(o);} 1361 public int lastIndexOf(Object o) {return list.lastIndexOf(o);} 1362 public boolean addAll(int index, Collection<? extends E> c) { 1363 throw new UnsupportedOperationException(); 1364 } 1365 1366 @Override 1367 public void replaceAll(UnaryOperator<E> operator) { 1368 throw new UnsupportedOperationException(); 1369 } 1370 @Override 1371 public void sort(Comparator<? super E> c) { 1372 throw new UnsupportedOperationException(); 1373 } 1374 1375 public ListIterator<E> listIterator() {return listIterator(0);} 1376 1377 public ListIterator<E> listIterator(final int index) { 1378 return new ListIterator<E>() { 1379 private final ListIterator<? extends E> i 1380 = list.listIterator(index); 1381 1382 public boolean hasNext() {return i.hasNext();} 1383 public E next() {return i.next();} 1384 public boolean hasPrevious() {return i.hasPrevious();} 1385 public E previous() {return i.previous();} 1386 public int nextIndex() {return i.nextIndex();} 1387 public int previousIndex() {return i.previousIndex();} 1388 1389 public void remove() { 1390 throw new UnsupportedOperationException(); 1391 } 1392 public void set(E e) { 1393 throw new UnsupportedOperationException(); 1394 } 1395 public void add(E e) { 1396 throw new UnsupportedOperationException(); 1397 } 1398 1399 @Override 1400 public void forEachRemaining(Consumer<? super E> action) { 1401 i.forEachRemaining(action); 1402 } 1403 }; 1404 } 1405 1406 public List<E> subList(int fromIndex, int toIndex) { 1407 return new UnmodifiableList<>(list.subList(fromIndex, toIndex)); 1408 } 1409 1410 /** 1411 * UnmodifiableRandomAccessList instances are serialized as 1412 * UnmodifiableList instances to allow them to be deserialized 1413 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList). 1414 * This method inverts the transformation. As a beneficial 1415 * side-effect, it also grafts the RandomAccess marker onto 1416 * UnmodifiableList instances that were serialized in pre-1.4 JREs. 1417 * 1418 * Note: Unfortunately, UnmodifiableRandomAccessList instances 1419 * serialized in 1.4.1 and deserialized in 1.4 will become 1420 * UnmodifiableList instances, as this method was missing in 1.4. 1421 */ 1422 private Object readResolve() { 1423 return (list instanceof RandomAccess 1424 ? new UnmodifiableRandomAccessList<>(list) 1425 : this); 1426 } 1427 } 1428 1429 /** 1430 * @serial include 1431 */ 1432 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E> 1433 implements RandomAccess 1434 { 1435 UnmodifiableRandomAccessList(List<? extends E> list) { 1436 super(list); 1437 } 1438 1439 public List<E> subList(int fromIndex, int toIndex) { 1440 return new UnmodifiableRandomAccessList<>( 1441 list.subList(fromIndex, toIndex)); 1442 } 1443 1444 private static final long serialVersionUID = -2542308836966382001L; 1445 1446 /** 1447 * Allows instances to be deserialized in pre-1.4 JREs (which do 1448 * not have UnmodifiableRandomAccessList). UnmodifiableList has 1449 * a readResolve method that inverts this transformation upon 1450 * deserialization. 1451 */ 1452 private Object writeReplace() { 1453 return new UnmodifiableList<>(list); 1454 } 1455 } 1456 1457 /** 1458 * Returns an unmodifiable view of the specified map. This method 1459 * allows modules to provide users with "read-only" access to internal 1460 * maps. Query operations on the returned map "read through" 1461 * to the specified map, and attempts to modify the returned 1462 * map, whether direct or via its collection views, result in an 1463 * <tt>UnsupportedOperationException</tt>.<p> 1464 * 1465 * The returned map will be serializable if the specified map 1466 * is serializable. 1467 * 1468 * @param <K> the class of the map keys 1469 * @param <V> the class of the map values 1470 * @param m the map for which an unmodifiable view is to be returned. 1471 * @return an unmodifiable view of the specified map. 1472 */ 1473 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) { 1474 return new UnmodifiableMap<>(m); 1475 } 1476 1477 /** 1478 * @serial include 1479 */ 1480 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable { 1481 private static final long serialVersionUID = -1034234728574286014L; 1482 1483 private final Map<? extends K, ? extends V> m; 1484 1485 UnmodifiableMap(Map<? extends K, ? extends V> m) { 1486 if (m==null) 1487 throw new NullPointerException(); 1488 this.m = m; 1489 } 1490 1491 public int size() {return m.size();} 1492 public boolean isEmpty() {return m.isEmpty();} 1493 public boolean containsKey(Object key) {return m.containsKey(key);} 1494 public boolean containsValue(Object val) {return m.containsValue(val);} 1495 public V get(Object key) {return m.get(key);} 1496 1497 public V put(K key, V value) { 1498 throw new UnsupportedOperationException(); 1499 } 1500 public V remove(Object key) { 1501 throw new UnsupportedOperationException(); 1502 } 1503 public void putAll(Map<? extends K, ? extends V> m) { 1504 throw new UnsupportedOperationException(); 1505 } 1506 public void clear() { 1507 throw new UnsupportedOperationException(); 1508 } 1509 1510 private transient Set<K> keySet; 1511 private transient Set<Map.Entry<K,V>> entrySet; 1512 private transient Collection<V> values; 1513 1514 public Set<K> keySet() { 1515 if (keySet==null) 1516 keySet = unmodifiableSet(m.keySet()); 1517 return keySet; 1518 } 1519 1520 public Set<Map.Entry<K,V>> entrySet() { 1521 if (entrySet==null) 1522 entrySet = new UnmodifiableEntrySet<>(m.entrySet()); 1523 return entrySet; 1524 } 1525 1526 public Collection<V> values() { 1527 if (values==null) 1528 values = unmodifiableCollection(m.values()); 1529 return values; 1530 } 1531 1532 public boolean equals(Object o) {return o == this || m.equals(o);} 1533 public int hashCode() {return m.hashCode();} 1534 public String toString() {return m.toString();} 1535 1536 // Override default methods in Map 1537 @Override 1538 @SuppressWarnings("unchecked") 1539 public V getOrDefault(Object k, V defaultValue) { 1540 // Safe cast as we don't change the value 1541 return ((Map<K, V>)m).getOrDefault(k, defaultValue); 1542 } 1543 1544 @Override 1545 public void forEach(BiConsumer<? super K, ? super V> action) { 1546 m.forEach(action); 1547 } 1548 1549 @Override 1550 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 1551 throw new UnsupportedOperationException(); 1552 } 1553 1554 @Override 1555 public V putIfAbsent(K key, V value) { 1556 throw new UnsupportedOperationException(); 1557 } 1558 1559 @Override 1560 public boolean remove(Object key, Object value) { 1561 throw new UnsupportedOperationException(); 1562 } 1563 1564 @Override 1565 public boolean replace(K key, V oldValue, V newValue) { 1566 throw new UnsupportedOperationException(); 1567 } 1568 1569 @Override 1570 public V replace(K key, V value) { 1571 throw new UnsupportedOperationException(); 1572 } 1573 1574 @Override 1575 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) { 1576 throw new UnsupportedOperationException(); 1577 } 1578 1579 @Override 1580 public V computeIfPresent(K key, 1581 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 1582 throw new UnsupportedOperationException(); 1583 } 1584 1585 @Override 1586 public V compute(K key, 1587 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 1588 throw new UnsupportedOperationException(); 1589 } 1590 1591 @Override 1592 public V merge(K key, V value, 1593 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 1594 throw new UnsupportedOperationException(); 1595 } 1596 1597 /** 1598 * We need this class in addition to UnmodifiableSet as 1599 * Map.Entries themselves permit modification of the backing Map 1600 * via their setValue operation. This class is subtle: there are 1601 * many possible attacks that must be thwarted. 1602 * 1603 * @serial include 1604 */ 1605 static class UnmodifiableEntrySet<K,V> 1606 extends UnmodifiableSet<Map.Entry<K,V>> { 1607 private static final long serialVersionUID = 7854390611657943733L; 1608 1609 @SuppressWarnings({"unchecked", "rawtypes"}) 1610 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) { 1611 // Need to cast to raw in order to work around a limitation in the type system 1612 super((Set)s); 1613 } 1614 1615 static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) { 1616 return e -> action.accept(new UnmodifiableEntry<>(e)); 1617 } 1618 1619 public void forEach(Consumer<? super Entry<K, V>> action) { 1620 Objects.requireNonNull(action); 1621 c.forEach(entryConsumer(action)); 1622 } 1623 1624 static final class UnmodifiableEntrySetSpliterator<K, V> 1625 implements Spliterator<Entry<K,V>> { 1626 final Spliterator<Map.Entry<K, V>> s; 1627 1628 UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) { 1629 this.s = s; 1630 } 1631 1632 @Override 1633 public boolean tryAdvance(Consumer<? super Entry<K, V>> action) { 1634 Objects.requireNonNull(action); 1635 return s.tryAdvance(entryConsumer(action)); 1636 } 1637 1638 @Override 1639 public void forEachRemaining(Consumer<? super Entry<K, V>> action) { 1640 Objects.requireNonNull(action); 1641 s.forEachRemaining(entryConsumer(action)); 1642 } 1643 1644 @Override 1645 public Spliterator<Entry<K, V>> trySplit() { 1646 Spliterator<Entry<K, V>> split = s.trySplit(); 1647 return split == null 1648 ? null 1649 : new UnmodifiableEntrySetSpliterator<>(split); 1650 } 1651 1652 @Override 1653 public long estimateSize() { 1654 return s.estimateSize(); 1655 } 1656 1657 @Override 1658 public long getExactSizeIfKnown() { 1659 return s.getExactSizeIfKnown(); 1660 } 1661 1662 @Override 1663 public int characteristics() { 1664 return s.characteristics(); 1665 } 1666 1667 @Override 1668 public boolean hasCharacteristics(int characteristics) { 1669 return s.hasCharacteristics(characteristics); 1670 } 1671 1672 @Override 1673 public Comparator<? super Entry<K, V>> getComparator() { 1674 return s.getComparator(); 1675 } 1676 } 1677 1678 @SuppressWarnings("unchecked") 1679 public Spliterator<Entry<K,V>> spliterator() { 1680 return new UnmodifiableEntrySetSpliterator<>( 1681 (Spliterator<Map.Entry<K, V>>) c.spliterator()); 1682 } 1683 1684 @Override 1685 public Stream<Entry<K,V>> stream() { 1686 return StreamSupport.stream(spliterator(), false); 1687 } 1688 1689 @Override 1690 public Stream<Entry<K,V>> parallelStream() { 1691 return StreamSupport.stream(spliterator(), true); 1692 } 1693 1694 public Iterator<Map.Entry<K,V>> iterator() { 1695 return new Iterator<Map.Entry<K,V>>() { 1696 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator(); 1697 1698 public boolean hasNext() { 1699 return i.hasNext(); 1700 } 1701 public Map.Entry<K,V> next() { 1702 return new UnmodifiableEntry<>(i.next()); 1703 } 1704 public void remove() { 1705 throw new UnsupportedOperationException(); 1706 } 1707 // Android-note: This seems pretty inconsistent. Unlike other subclasses, we aren't 1708 // delegating to the subclass iterator here. Seems like an oversight. 1709 }; 1710 } 1711 1712 @SuppressWarnings("unchecked") 1713 public Object[] toArray() { 1714 Object[] a = c.toArray(); 1715 for (int i=0; i<a.length; i++) 1716 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]); 1717 return a; 1718 } 1719 1720 @SuppressWarnings("unchecked") 1721 public <T> T[] toArray(T[] a) { 1722 // We don't pass a to c.toArray, to avoid window of 1723 // vulnerability wherein an unscrupulous multithreaded client 1724 // could get his hands on raw (unwrapped) Entries from c. 1725 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); 1726 1727 for (int i=0; i<arr.length; i++) 1728 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]); 1729 1730 if (arr.length > a.length) 1731 return (T[])arr; 1732 1733 System.arraycopy(arr, 0, a, 0, arr.length); 1734 if (a.length > arr.length) 1735 a[arr.length] = null; 1736 return a; 1737 } 1738 1739 /** 1740 * This method is overridden to protect the backing set against 1741 * an object with a nefarious equals function that senses 1742 * that the equality-candidate is Map.Entry and calls its 1743 * setValue method. 1744 */ 1745 public boolean contains(Object o) { 1746 if (!(o instanceof Map.Entry)) 1747 return false; 1748 return c.contains( 1749 new UnmodifiableEntry<>((Map.Entry<?,?>) o)); 1750 } 1751 1752 /** 1753 * The next two methods are overridden to protect against 1754 * an unscrupulous List whose contains(Object o) method senses 1755 * when o is a Map.Entry, and calls o.setValue. 1756 */ 1757 public boolean containsAll(Collection<?> coll) { 1758 for (Object e : coll) { 1759 if (!contains(e)) // Invokes safe contains() above 1760 return false; 1761 } 1762 return true; 1763 } 1764 public boolean equals(Object o) { 1765 if (o == this) 1766 return true; 1767 1768 if (!(o instanceof Set)) 1769 return false; 1770 Set<?> s = (Set<?>) o; 1771 if (s.size() != c.size()) 1772 return false; 1773 return containsAll(s); // Invokes safe containsAll() above 1774 } 1775 1776 /** 1777 * This "wrapper class" serves two purposes: it prevents 1778 * the client from modifying the backing Map, by short-circuiting 1779 * the setValue method, and it protects the backing Map against 1780 * an ill-behaved Map.Entry that attempts to modify another 1781 * Map Entry when asked to perform an equality check. 1782 */ 1783 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> { 1784 private Map.Entry<? extends K, ? extends V> e; 1785 1786 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e) 1787 {this.e = Objects.requireNonNull(e);} 1788 1789 public K getKey() {return e.getKey();} 1790 public V getValue() {return e.getValue();} 1791 public V setValue(V value) { 1792 throw new UnsupportedOperationException(); 1793 } 1794 public int hashCode() {return e.hashCode();} 1795 public boolean equals(Object o) { 1796 if (this == o) 1797 return true; 1798 if (!(o instanceof Map.Entry)) 1799 return false; 1800 Map.Entry<?,?> t = (Map.Entry<?,?>)o; 1801 return eq(e.getKey(), t.getKey()) && 1802 eq(e.getValue(), t.getValue()); 1803 } 1804 public String toString() {return e.toString();} 1805 } 1806 } 1807 } 1808 1809 /** 1810 * Returns an unmodifiable view of the specified sorted map. This method 1811 * allows modules to provide users with "read-only" access to internal 1812 * sorted maps. Query operations on the returned sorted map "read through" 1813 * to the specified sorted map. Attempts to modify the returned 1814 * sorted map, whether direct, via its collection views, or via its 1815 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in 1816 * an <tt>UnsupportedOperationException</tt>.<p> 1817 * 1818 * The returned sorted map will be serializable if the specified sorted map 1819 * is serializable. 1820 * 1821 * @param <K> the class of the map keys 1822 * @param <V> the class of the map values 1823 * @param m the sorted map for which an unmodifiable view is to be 1824 * returned. 1825 * @return an unmodifiable view of the specified sorted map. 1826 */ 1827 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) { 1828 return new UnmodifiableSortedMap<>(m); 1829 } 1830 1831 /** 1832 * @serial include 1833 */ 1834 static class UnmodifiableSortedMap<K,V> 1835 extends UnmodifiableMap<K,V> 1836 implements SortedMap<K,V>, Serializable { 1837 private static final long serialVersionUID = -8806743815996713206L; 1838 1839 private final SortedMap<K, ? extends V> sm; 1840 1841 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; } 1842 public Comparator<? super K> comparator() { return sm.comparator(); } 1843 public SortedMap<K,V> subMap(K fromKey, K toKey) 1844 { return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); } 1845 public SortedMap<K,V> headMap(K toKey) 1846 { return new UnmodifiableSortedMap<>(sm.headMap(toKey)); } 1847 public SortedMap<K,V> tailMap(K fromKey) 1848 { return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); } 1849 public K firstKey() { return sm.firstKey(); } 1850 public K lastKey() { return sm.lastKey(); } 1851 } 1852 1853 /** 1854 * Returns an unmodifiable view of the specified navigable map. This method 1855 * allows modules to provide users with "read-only" access to internal 1856 * navigable maps. Query operations on the returned navigable map "read 1857 * through" to the specified navigable map. Attempts to modify the returned 1858 * navigable map, whether direct, via its collection views, or via its 1859 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in 1860 * an {@code UnsupportedOperationException}.<p> 1861 * 1862 * The returned navigable map will be serializable if the specified 1863 * navigable map is serializable. 1864 * 1865 * @param <K> the class of the map keys 1866 * @param <V> the class of the map values 1867 * @param m the navigable map for which an unmodifiable view is to be 1868 * returned 1869 * @return an unmodifiable view of the specified navigable map 1870 * @since 1.8 1871 */ 1872 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) { 1873 return new UnmodifiableNavigableMap<>(m); 1874 } 1875 1876 /** 1877 * @serial include 1878 */ 1879 static class UnmodifiableNavigableMap<K,V> 1880 extends UnmodifiableSortedMap<K,V> 1881 implements NavigableMap<K,V>, Serializable { 1882 private static final long serialVersionUID = -4858195264774772197L; 1883 1884 /** 1885 * A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve 1886 * to preserve singleton property. 1887 * 1888 * @param <K> type of keys, if there were any, and of bounds 1889 * @param <V> type of values, if there were any 1890 */ 1891 private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V> 1892 implements Serializable { 1893 1894 private static final long serialVersionUID = -2239321462712562324L; 1895 1896 EmptyNavigableMap() { super(new TreeMap<K,V>()); } 1897 1898 @Override 1899 public NavigableSet<K> navigableKeySet() 1900 { return emptyNavigableSet(); } 1901 1902 private Object readResolve() { return EMPTY_NAVIGABLE_MAP; } 1903 } 1904 1905 /** 1906 * Singleton for {@link emptyNavigableMap()} which is also immutable. 1907 */ 1908 private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP = 1909 new EmptyNavigableMap<>(); 1910 1911 /** 1912 * The instance we wrap and protect. 1913 */ 1914 private final NavigableMap<K, ? extends V> nm; 1915 1916 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m) 1917 {super(m); nm = m;} 1918 1919 public K lowerKey(K key) { return nm.lowerKey(key); } 1920 public K floorKey(K key) { return nm.floorKey(key); } 1921 public K ceilingKey(K key) { return nm.ceilingKey(key); } 1922 public K higherKey(K key) { return nm.higherKey(key); } 1923 1924 @SuppressWarnings("unchecked") 1925 public Entry<K, V> lowerEntry(K key) { 1926 Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key); 1927 return (null != lower) 1928 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(lower) 1929 : null; 1930 } 1931 1932 @SuppressWarnings("unchecked") 1933 public Entry<K, V> floorEntry(K key) { 1934 Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key); 1935 return (null != floor) 1936 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(floor) 1937 : null; 1938 } 1939 1940 @SuppressWarnings("unchecked") 1941 public Entry<K, V> ceilingEntry(K key) { 1942 Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key); 1943 return (null != ceiling) 1944 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(ceiling) 1945 : null; 1946 } 1947 1948 1949 @SuppressWarnings("unchecked") 1950 public Entry<K, V> higherEntry(K key) { 1951 Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key); 1952 return (null != higher) 1953 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(higher) 1954 : null; 1955 } 1956 1957 @SuppressWarnings("unchecked") 1958 public Entry<K, V> firstEntry() { 1959 Entry<K,V> first = (Entry<K, V>) nm.firstEntry(); 1960 return (null != first) 1961 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(first) 1962 : null; 1963 } 1964 1965 @SuppressWarnings("unchecked") 1966 public Entry<K, V> lastEntry() { 1967 Entry<K,V> last = (Entry<K, V>) nm.lastEntry(); 1968 return (null != last) 1969 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(last) 1970 : null; 1971 } 1972 1973 public Entry<K, V> pollFirstEntry() 1974 { throw new UnsupportedOperationException(); } 1975 public Entry<K, V> pollLastEntry() 1976 { throw new UnsupportedOperationException(); } 1977 public NavigableMap<K, V> descendingMap() 1978 { return unmodifiableNavigableMap(nm.descendingMap()); } 1979 public NavigableSet<K> navigableKeySet() 1980 { return unmodifiableNavigableSet(nm.navigableKeySet()); } 1981 public NavigableSet<K> descendingKeySet() 1982 { return unmodifiableNavigableSet(nm.descendingKeySet()); } 1983 1984 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 1985 return unmodifiableNavigableMap( 1986 nm.subMap(fromKey, fromInclusive, toKey, toInclusive)); 1987 } 1988 1989 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) 1990 { return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); } 1991 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) 1992 { return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); } 1993 } 1994 1995 // Synch Wrappers 1996 1997 /** 1998 * Returns a synchronized (thread-safe) collection backed by the specified 1999 * collection. In order to guarantee serial access, it is critical that 2000 * <strong>all</strong> access to the backing collection is accomplished 2001 * through the returned collection.<p> 2002 * 2003 * It is imperative that the user manually synchronize on the returned 2004 * collection when traversing it via {@link Iterator}, {@link Spliterator} 2005 * or {@link Stream}: 2006 * <pre> 2007 * Collection c = Collections.synchronizedCollection(myCollection); 2008 * ... 2009 * synchronized (c) { 2010 * Iterator i = c.iterator(); // Must be in the synchronized block 2011 * while (i.hasNext()) 2012 * foo(i.next()); 2013 * } 2014 * </pre> 2015 * Failure to follow this advice may result in non-deterministic behavior. 2016 * 2017 * <p>The returned collection does <i>not</i> pass the {@code hashCode} 2018 * and {@code equals} operations through to the backing collection, but 2019 * relies on {@code Object}'s equals and hashCode methods. This is 2020 * necessary to preserve the contracts of these operations in the case 2021 * that the backing collection is a set or a list.<p> 2022 * 2023 * The returned collection will be serializable if the specified collection 2024 * is serializable. 2025 * 2026 * @param <T> the class of the objects in the collection 2027 * @param c the collection to be "wrapped" in a synchronized collection. 2028 * @return a synchronized view of the specified collection. 2029 */ 2030 public static <T> Collection<T> synchronizedCollection(Collection<T> c) { 2031 return new SynchronizedCollection<>(c); 2032 } 2033 2034 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) { 2035 return new SynchronizedCollection<>(c, mutex); 2036 } 2037 2038 /** 2039 * @serial include 2040 */ 2041 static class SynchronizedCollection<E> implements Collection<E>, Serializable { 2042 private static final long serialVersionUID = 3053995032091335093L; 2043 2044 final Collection<E> c; // Backing Collection 2045 final Object mutex; // Object on which to synchronize 2046 2047 SynchronizedCollection(Collection<E> c) { 2048 this.c = Objects.requireNonNull(c); 2049 mutex = this; 2050 } 2051 2052 SynchronizedCollection(Collection<E> c, Object mutex) { 2053 this.c = Objects.requireNonNull(c); 2054 this.mutex = Objects.requireNonNull(mutex); 2055 } 2056 2057 public int size() { 2058 synchronized (mutex) {return c.size();} 2059 } 2060 public boolean isEmpty() { 2061 synchronized (mutex) {return c.isEmpty();} 2062 } 2063 public boolean contains(Object o) { 2064 synchronized (mutex) {return c.contains(o);} 2065 } 2066 public Object[] toArray() { 2067 synchronized (mutex) {return c.toArray();} 2068 } 2069 public <T> T[] toArray(T[] a) { 2070 synchronized (mutex) {return c.toArray(a);} 2071 } 2072 2073 public Iterator<E> iterator() { 2074 return c.iterator(); // Must be manually synched by user! 2075 } 2076 2077 public boolean add(E e) { 2078 synchronized (mutex) {return c.add(e);} 2079 } 2080 public boolean remove(Object o) { 2081 synchronized (mutex) {return c.remove(o);} 2082 } 2083 2084 public boolean containsAll(Collection<?> coll) { 2085 synchronized (mutex) {return c.containsAll(coll);} 2086 } 2087 public boolean addAll(Collection<? extends E> coll) { 2088 synchronized (mutex) {return c.addAll(coll);} 2089 } 2090 public boolean removeAll(Collection<?> coll) { 2091 synchronized (mutex) {return c.removeAll(coll);} 2092 } 2093 public boolean retainAll(Collection<?> coll) { 2094 synchronized (mutex) {return c.retainAll(coll);} 2095 } 2096 public void clear() { 2097 synchronized (mutex) {c.clear();} 2098 } 2099 public String toString() { 2100 synchronized (mutex) {return c.toString();} 2101 } 2102 // Override default methods in Collection 2103 @Override 2104 public void forEach(Consumer<? super E> consumer) { 2105 synchronized (mutex) {c.forEach(consumer);} 2106 } 2107 @Override 2108 public boolean removeIf(Predicate<? super E> filter) { 2109 synchronized (mutex) {return c.removeIf(filter);} 2110 } 2111 @Override 2112 public Spliterator<E> spliterator() { 2113 return c.spliterator(); // Must be manually synched by user! 2114 } 2115 @Override 2116 public Stream<E> stream() { 2117 return c.stream(); // Must be manually synched by user! 2118 } 2119 @Override 2120 public Stream<E> parallelStream() { 2121 return c.parallelStream(); // Must be manually synched by user! 2122 } 2123 private void writeObject(ObjectOutputStream s) throws IOException { 2124 synchronized (mutex) {s.defaultWriteObject();} 2125 } 2126 } 2127 2128 /** 2129 * Returns a synchronized (thread-safe) set backed by the specified 2130 * set. In order to guarantee serial access, it is critical that 2131 * <strong>all</strong> access to the backing set is accomplished 2132 * through the returned set.<p> 2133 * 2134 * It is imperative that the user manually synchronize on the returned 2135 * set when iterating over it: 2136 * <pre> 2137 * Set s = Collections.synchronizedSet(new HashSet()); 2138 * ... 2139 * synchronized (s) { 2140 * Iterator i = s.iterator(); // Must be in the synchronized block 2141 * while (i.hasNext()) 2142 * foo(i.next()); 2143 * } 2144 * </pre> 2145 * Failure to follow this advice may result in non-deterministic behavior. 2146 * 2147 * <p>The returned set will be serializable if the specified set is 2148 * serializable. 2149 * 2150 * @param <T> the class of the objects in the set 2151 * @param s the set to be "wrapped" in a synchronized set. 2152 * @return a synchronized view of the specified set. 2153 */ 2154 public static <T> Set<T> synchronizedSet(Set<T> s) { 2155 return new SynchronizedSet<>(s); 2156 } 2157 2158 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) { 2159 return new SynchronizedSet<>(s, mutex); 2160 } 2161 2162 /** 2163 * @serial include 2164 */ 2165 static class SynchronizedSet<E> 2166 extends SynchronizedCollection<E> 2167 implements Set<E> { 2168 private static final long serialVersionUID = 487447009682186044L; 2169 2170 SynchronizedSet(Set<E> s) { 2171 super(s); 2172 } 2173 SynchronizedSet(Set<E> s, Object mutex) { 2174 super(s, mutex); 2175 } 2176 2177 public boolean equals(Object o) { 2178 if (this == o) 2179 return true; 2180 synchronized (mutex) {return c.equals(o);} 2181 } 2182 public int hashCode() { 2183 synchronized (mutex) {return c.hashCode();} 2184 } 2185 } 2186 2187 /** 2188 * Returns a synchronized (thread-safe) sorted set backed by the specified 2189 * sorted set. In order to guarantee serial access, it is critical that 2190 * <strong>all</strong> access to the backing sorted set is accomplished 2191 * through the returned sorted set (or its views).<p> 2192 * 2193 * It is imperative that the user manually synchronize on the returned 2194 * sorted set when iterating over it or any of its <tt>subSet</tt>, 2195 * <tt>headSet</tt>, or <tt>tailSet</tt> views. 2196 * <pre> 2197 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); 2198 * ... 2199 * synchronized (s) { 2200 * Iterator i = s.iterator(); // Must be in the synchronized block 2201 * while (i.hasNext()) 2202 * foo(i.next()); 2203 * } 2204 * </pre> 2205 * or: 2206 * <pre> 2207 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); 2208 * SortedSet s2 = s.headSet(foo); 2209 * ... 2210 * synchronized (s) { // Note: s, not s2!!! 2211 * Iterator i = s2.iterator(); // Must be in the synchronized block 2212 * while (i.hasNext()) 2213 * foo(i.next()); 2214 * } 2215 * </pre> 2216 * Failure to follow this advice may result in non-deterministic behavior. 2217 * 2218 * <p>The returned sorted set will be serializable if the specified 2219 * sorted set is serializable. 2220 * 2221 * @param <T> the class of the objects in the set 2222 * @param s the sorted set to be "wrapped" in a synchronized sorted set. 2223 * @return a synchronized view of the specified sorted set. 2224 */ 2225 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) { 2226 return new SynchronizedSortedSet<>(s); 2227 } 2228 2229 /** 2230 * @serial include 2231 */ 2232 static class SynchronizedSortedSet<E> 2233 extends SynchronizedSet<E> 2234 implements SortedSet<E> 2235 { 2236 private static final long serialVersionUID = 8695801310862127406L; 2237 2238 private final SortedSet<E> ss; 2239 2240 SynchronizedSortedSet(SortedSet<E> s) { 2241 super(s); 2242 ss = s; 2243 } 2244 SynchronizedSortedSet(SortedSet<E> s, Object mutex) { 2245 super(s, mutex); 2246 ss = s; 2247 } 2248 2249 public Comparator<? super E> comparator() { 2250 synchronized (mutex) {return ss.comparator();} 2251 } 2252 2253 public SortedSet<E> subSet(E fromElement, E toElement) { 2254 synchronized (mutex) { 2255 return new SynchronizedSortedSet<>( 2256 ss.subSet(fromElement, toElement), mutex); 2257 } 2258 } 2259 public SortedSet<E> headSet(E toElement) { 2260 synchronized (mutex) { 2261 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex); 2262 } 2263 } 2264 public SortedSet<E> tailSet(E fromElement) { 2265 synchronized (mutex) { 2266 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex); 2267 } 2268 } 2269 2270 public E first() { 2271 synchronized (mutex) {return ss.first();} 2272 } 2273 public E last() { 2274 synchronized (mutex) {return ss.last();} 2275 } 2276 } 2277 2278 /** 2279 * Returns a synchronized (thread-safe) navigable set backed by the 2280 * specified navigable set. In order to guarantee serial access, it is 2281 * critical that <strong>all</strong> access to the backing navigable set is 2282 * accomplished through the returned navigable set (or its views).<p> 2283 * 2284 * It is imperative that the user manually synchronize on the returned 2285 * navigable set when iterating over it or any of its {@code subSet}, 2286 * {@code headSet}, or {@code tailSet} views. 2287 * <pre> 2288 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet()); 2289 * ... 2290 * synchronized (s) { 2291 * Iterator i = s.iterator(); // Must be in the synchronized block 2292 * while (i.hasNext()) 2293 * foo(i.next()); 2294 * } 2295 * </pre> 2296 * or: 2297 * <pre> 2298 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet()); 2299 * NavigableSet s2 = s.headSet(foo, true); 2300 * ... 2301 * synchronized (s) { // Note: s, not s2!!! 2302 * Iterator i = s2.iterator(); // Must be in the synchronized block 2303 * while (i.hasNext()) 2304 * foo(i.next()); 2305 * } 2306 * </pre> 2307 * Failure to follow this advice may result in non-deterministic behavior. 2308 * 2309 * <p>The returned navigable set will be serializable if the specified 2310 * navigable set is serializable. 2311 * 2312 * @param <T> the class of the objects in the set 2313 * @param s the navigable set to be "wrapped" in a synchronized navigable 2314 * set 2315 * @return a synchronized view of the specified navigable set 2316 * @since 1.8 2317 */ 2318 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) { 2319 return new SynchronizedNavigableSet<>(s); 2320 } 2321 2322 /** 2323 * @serial include 2324 */ 2325 static class SynchronizedNavigableSet<E> 2326 extends SynchronizedSortedSet<E> 2327 implements NavigableSet<E> 2328 { 2329 private static final long serialVersionUID = -5505529816273629798L; 2330 2331 private final NavigableSet<E> ns; 2332 2333 SynchronizedNavigableSet(NavigableSet<E> s) { 2334 super(s); 2335 ns = s; 2336 } 2337 2338 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) { 2339 super(s, mutex); 2340 ns = s; 2341 } 2342 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} } 2343 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} } 2344 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} } 2345 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} } 2346 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} } 2347 public E pollLast() { synchronized (mutex) {return ns.pollLast();} } 2348 2349 public NavigableSet<E> descendingSet() { 2350 synchronized (mutex) { 2351 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex); 2352 } 2353 } 2354 2355 public Iterator<E> descendingIterator() 2356 { synchronized (mutex) { return descendingSet().iterator(); } } 2357 2358 public NavigableSet<E> subSet(E fromElement, E toElement) { 2359 synchronized (mutex) { 2360 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex); 2361 } 2362 } 2363 public NavigableSet<E> headSet(E toElement) { 2364 synchronized (mutex) { 2365 return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex); 2366 } 2367 } 2368 public NavigableSet<E> tailSet(E fromElement) { 2369 synchronized (mutex) { 2370 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, true), mutex); 2371 } 2372 } 2373 2374 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 2375 synchronized (mutex) { 2376 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex); 2377 } 2378 } 2379 2380 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 2381 synchronized (mutex) { 2382 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex); 2383 } 2384 } 2385 2386 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 2387 synchronized (mutex) { 2388 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive), mutex); 2389 } 2390 } 2391 } 2392 2393 /** 2394 * Returns a synchronized (thread-safe) list backed by the specified 2395 * list. In order to guarantee serial access, it is critical that 2396 * <strong>all</strong> access to the backing list is accomplished 2397 * through the returned list.<p> 2398 * 2399 * It is imperative that the user manually synchronize on the returned 2400 * list when iterating over it: 2401 * <pre> 2402 * List list = Collections.synchronizedList(new ArrayList()); 2403 * ... 2404 * synchronized (list) { 2405 * Iterator i = list.iterator(); // Must be in synchronized block 2406 * while (i.hasNext()) 2407 * foo(i.next()); 2408 * } 2409 * </pre> 2410 * Failure to follow this advice may result in non-deterministic behavior. 2411 * 2412 * <p>The returned list will be serializable if the specified list is 2413 * serializable. 2414 * 2415 * @param <T> the class of the objects in the list 2416 * @param list the list to be "wrapped" in a synchronized list. 2417 * @return a synchronized view of the specified list. 2418 */ 2419 public static <T> List<T> synchronizedList(List<T> list) { 2420 return (list instanceof RandomAccess ? 2421 new SynchronizedRandomAccessList<>(list) : 2422 new SynchronizedList<>(list)); 2423 } 2424 2425 static <T> List<T> synchronizedList(List<T> list, Object mutex) { 2426 return (list instanceof RandomAccess ? 2427 new SynchronizedRandomAccessList<>(list, mutex) : 2428 new SynchronizedList<>(list, mutex)); 2429 } 2430 2431 /** 2432 * @serial include 2433 */ 2434 static class SynchronizedList<E> 2435 extends SynchronizedCollection<E> 2436 implements List<E> { 2437 private static final long serialVersionUID = -7754090372962971524L; 2438 2439 final List<E> list; 2440 2441 SynchronizedList(List<E> list) { 2442 super(list); 2443 this.list = list; 2444 } 2445 SynchronizedList(List<E> list, Object mutex) { 2446 super(list, mutex); 2447 this.list = list; 2448 } 2449 2450 public boolean equals(Object o) { 2451 if (this == o) 2452 return true; 2453 synchronized (mutex) {return list.equals(o);} 2454 } 2455 public int hashCode() { 2456 synchronized (mutex) {return list.hashCode();} 2457 } 2458 2459 public E get(int index) { 2460 synchronized (mutex) {return list.get(index);} 2461 } 2462 public E set(int index, E element) { 2463 synchronized (mutex) {return list.set(index, element);} 2464 } 2465 public void add(int index, E element) { 2466 synchronized (mutex) {list.add(index, element);} 2467 } 2468 public E remove(int index) { 2469 synchronized (mutex) {return list.remove(index);} 2470 } 2471 2472 public int indexOf(Object o) { 2473 synchronized (mutex) {return list.indexOf(o);} 2474 } 2475 public int lastIndexOf(Object o) { 2476 synchronized (mutex) {return list.lastIndexOf(o);} 2477 } 2478 2479 public boolean addAll(int index, Collection<? extends E> c) { 2480 synchronized (mutex) {return list.addAll(index, c);} 2481 } 2482 2483 public ListIterator<E> listIterator() { 2484 return list.listIterator(); // Must be manually synched by user 2485 } 2486 2487 public ListIterator<E> listIterator(int index) { 2488 return list.listIterator(index); // Must be manually synched by user 2489 } 2490 2491 public List<E> subList(int fromIndex, int toIndex) { 2492 synchronized (mutex) { 2493 return new SynchronizedList<>(list.subList(fromIndex, toIndex), 2494 mutex); 2495 } 2496 } 2497 2498 @Override 2499 public void replaceAll(UnaryOperator<E> operator) { 2500 synchronized (mutex) {list.replaceAll(operator);} 2501 } 2502 @Override 2503 public void sort(Comparator<? super E> c) { 2504 synchronized (mutex) {list.sort(c);} 2505 } 2506 2507 /** 2508 * SynchronizedRandomAccessList instances are serialized as 2509 * SynchronizedList instances to allow them to be deserialized 2510 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList). 2511 * This method inverts the transformation. As a beneficial 2512 * side-effect, it also grafts the RandomAccess marker onto 2513 * SynchronizedList instances that were serialized in pre-1.4 JREs. 2514 * 2515 * Note: Unfortunately, SynchronizedRandomAccessList instances 2516 * serialized in 1.4.1 and deserialized in 1.4 will become 2517 * SynchronizedList instances, as this method was missing in 1.4. 2518 */ 2519 private Object readResolve() { 2520 return (list instanceof RandomAccess 2521 ? new SynchronizedRandomAccessList<>(list) 2522 : this); 2523 } 2524 } 2525 2526 /** 2527 * @serial include 2528 */ 2529 static class SynchronizedRandomAccessList<E> 2530 extends SynchronizedList<E> 2531 implements RandomAccess { 2532 2533 SynchronizedRandomAccessList(List<E> list) { 2534 super(list); 2535 } 2536 2537 SynchronizedRandomAccessList(List<E> list, Object mutex) { 2538 super(list, mutex); 2539 } 2540 2541 public List<E> subList(int fromIndex, int toIndex) { 2542 synchronized (mutex) { 2543 return new SynchronizedRandomAccessList<>( 2544 list.subList(fromIndex, toIndex), mutex); 2545 } 2546 } 2547 2548 private static final long serialVersionUID = 1530674583602358482L; 2549 2550 /** 2551 * Allows instances to be deserialized in pre-1.4 JREs (which do 2552 * not have SynchronizedRandomAccessList). SynchronizedList has 2553 * a readResolve method that inverts this transformation upon 2554 * deserialization. 2555 */ 2556 private Object writeReplace() { 2557 return new SynchronizedList<>(list); 2558 } 2559 } 2560 2561 /** 2562 * Returns a synchronized (thread-safe) map backed by the specified 2563 * map. In order to guarantee serial access, it is critical that 2564 * <strong>all</strong> access to the backing map is accomplished 2565 * through the returned map.<p> 2566 * 2567 * It is imperative that the user manually synchronize on the returned 2568 * map when iterating over any of its collection views: 2569 * <pre> 2570 * Map m = Collections.synchronizedMap(new HashMap()); 2571 * ... 2572 * Set s = m.keySet(); // Needn't be in synchronized block 2573 * ... 2574 * synchronized (m) { // Synchronizing on m, not s! 2575 * Iterator i = s.iterator(); // Must be in synchronized block 2576 * while (i.hasNext()) 2577 * foo(i.next()); 2578 * } 2579 * </pre> 2580 * Failure to follow this advice may result in non-deterministic behavior. 2581 * 2582 * <p>The returned map will be serializable if the specified map is 2583 * serializable. 2584 * 2585 * @param <K> the class of the map keys 2586 * @param <V> the class of the map values 2587 * @param m the map to be "wrapped" in a synchronized map. 2588 * @return a synchronized view of the specified map. 2589 */ 2590 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) { 2591 return new SynchronizedMap<>(m); 2592 } 2593 2594 /** 2595 * @serial include 2596 */ 2597 private static class SynchronizedMap<K,V> 2598 implements Map<K,V>, Serializable { 2599 private static final long serialVersionUID = 1978198479659022715L; 2600 2601 private final Map<K,V> m; // Backing Map 2602 final Object mutex; // Object on which to synchronize 2603 2604 SynchronizedMap(Map<K,V> m) { 2605 this.m = Objects.requireNonNull(m); 2606 mutex = this; 2607 } 2608 2609 SynchronizedMap(Map<K,V> m, Object mutex) { 2610 this.m = m; 2611 this.mutex = mutex; 2612 } 2613 2614 public int size() { 2615 synchronized (mutex) {return m.size();} 2616 } 2617 public boolean isEmpty() { 2618 synchronized (mutex) {return m.isEmpty();} 2619 } 2620 public boolean containsKey(Object key) { 2621 synchronized (mutex) {return m.containsKey(key);} 2622 } 2623 public boolean containsValue(Object value) { 2624 synchronized (mutex) {return m.containsValue(value);} 2625 } 2626 public V get(Object key) { 2627 synchronized (mutex) {return m.get(key);} 2628 } 2629 2630 public V put(K key, V value) { 2631 synchronized (mutex) {return m.put(key, value);} 2632 } 2633 public V remove(Object key) { 2634 synchronized (mutex) {return m.remove(key);} 2635 } 2636 public void putAll(Map<? extends K, ? extends V> map) { 2637 synchronized (mutex) {m.putAll(map);} 2638 } 2639 public void clear() { 2640 synchronized (mutex) {m.clear();} 2641 } 2642 2643 private transient Set<K> keySet; 2644 private transient Set<Map.Entry<K,V>> entrySet; 2645 private transient Collection<V> values; 2646 2647 public Set<K> keySet() { 2648 synchronized (mutex) { 2649 if (keySet==null) 2650 keySet = new SynchronizedSet<>(m.keySet(), mutex); 2651 return keySet; 2652 } 2653 } 2654 2655 public Set<Map.Entry<K,V>> entrySet() { 2656 synchronized (mutex) { 2657 if (entrySet==null) 2658 entrySet = new SynchronizedSet<>(m.entrySet(), mutex); 2659 return entrySet; 2660 } 2661 } 2662 2663 public Collection<V> values() { 2664 synchronized (mutex) { 2665 if (values==null) 2666 values = new SynchronizedCollection<>(m.values(), mutex); 2667 return values; 2668 } 2669 } 2670 2671 public boolean equals(Object o) { 2672 if (this == o) 2673 return true; 2674 synchronized (mutex) {return m.equals(o);} 2675 } 2676 public int hashCode() { 2677 synchronized (mutex) {return m.hashCode();} 2678 } 2679 public String toString() { 2680 synchronized (mutex) {return m.toString();} 2681 } 2682 2683 // Override default methods in Map 2684 @Override 2685 public V getOrDefault(Object k, V defaultValue) { 2686 synchronized (mutex) {return m.getOrDefault(k, defaultValue);} 2687 } 2688 @Override 2689 public void forEach(BiConsumer<? super K, ? super V> action) { 2690 synchronized (mutex) {m.forEach(action);} 2691 } 2692 @Override 2693 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 2694 synchronized (mutex) {m.replaceAll(function);} 2695 } 2696 @Override 2697 public V putIfAbsent(K key, V value) { 2698 synchronized (mutex) {return m.putIfAbsent(key, value);} 2699 } 2700 @Override 2701 public boolean remove(Object key, Object value) { 2702 synchronized (mutex) {return m.remove(key, value);} 2703 } 2704 @Override 2705 public boolean replace(K key, V oldValue, V newValue) { 2706 synchronized (mutex) {return m.replace(key, oldValue, newValue);} 2707 } 2708 @Override 2709 public V replace(K key, V value) { 2710 synchronized (mutex) {return m.replace(key, value);} 2711 } 2712 @Override 2713 public V computeIfAbsent(K key, 2714 Function<? super K, ? extends V> mappingFunction) { 2715 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);} 2716 } 2717 @Override 2718 public V computeIfPresent(K key, 2719 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 2720 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);} 2721 } 2722 @Override 2723 public V compute(K key, 2724 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 2725 synchronized (mutex) {return m.compute(key, remappingFunction);} 2726 } 2727 @Override 2728 public V merge(K key, V value, 2729 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 2730 synchronized (mutex) {return m.merge(key, value, remappingFunction);} 2731 } 2732 2733 private void writeObject(ObjectOutputStream s) throws IOException { 2734 synchronized (mutex) {s.defaultWriteObject();} 2735 } 2736 } 2737 2738 /** 2739 * Returns a synchronized (thread-safe) sorted map backed by the specified 2740 * sorted map. In order to guarantee serial access, it is critical that 2741 * <strong>all</strong> access to the backing sorted map is accomplished 2742 * through the returned sorted map (or its views).<p> 2743 * 2744 * It is imperative that the user manually synchronize on the returned 2745 * sorted map when iterating over any of its collection views, or the 2746 * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or 2747 * <tt>tailMap</tt> views. 2748 * <pre> 2749 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); 2750 * ... 2751 * Set s = m.keySet(); // Needn't be in synchronized block 2752 * ... 2753 * synchronized (m) { // Synchronizing on m, not s! 2754 * Iterator i = s.iterator(); // Must be in synchronized block 2755 * while (i.hasNext()) 2756 * foo(i.next()); 2757 * } 2758 * </pre> 2759 * or: 2760 * <pre> 2761 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); 2762 * SortedMap m2 = m.subMap(foo, bar); 2763 * ... 2764 * Set s2 = m2.keySet(); // Needn't be in synchronized block 2765 * ... 2766 * synchronized (m) { // Synchronizing on m, not m2 or s2! 2767 * Iterator i = s.iterator(); // Must be in synchronized block 2768 * while (i.hasNext()) 2769 * foo(i.next()); 2770 * } 2771 * </pre> 2772 * Failure to follow this advice may result in non-deterministic behavior. 2773 * 2774 * <p>The returned sorted map will be serializable if the specified 2775 * sorted map is serializable. 2776 * 2777 * @param <K> the class of the map keys 2778 * @param <V> the class of the map values 2779 * @param m the sorted map to be "wrapped" in a synchronized sorted map. 2780 * @return a synchronized view of the specified sorted map. 2781 */ 2782 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) { 2783 return new SynchronizedSortedMap<>(m); 2784 } 2785 2786 /** 2787 * @serial include 2788 */ 2789 static class SynchronizedSortedMap<K,V> 2790 extends SynchronizedMap<K,V> 2791 implements SortedMap<K,V> 2792 { 2793 private static final long serialVersionUID = -8798146769416483793L; 2794 2795 private final SortedMap<K,V> sm; 2796 2797 SynchronizedSortedMap(SortedMap<K,V> m) { 2798 super(m); 2799 sm = m; 2800 } 2801 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) { 2802 super(m, mutex); 2803 sm = m; 2804 } 2805 2806 public Comparator<? super K> comparator() { 2807 synchronized (mutex) {return sm.comparator();} 2808 } 2809 2810 public SortedMap<K,V> subMap(K fromKey, K toKey) { 2811 synchronized (mutex) { 2812 return new SynchronizedSortedMap<>( 2813 sm.subMap(fromKey, toKey), mutex); 2814 } 2815 } 2816 public SortedMap<K,V> headMap(K toKey) { 2817 synchronized (mutex) { 2818 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex); 2819 } 2820 } 2821 public SortedMap<K,V> tailMap(K fromKey) { 2822 synchronized (mutex) { 2823 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex); 2824 } 2825 } 2826 2827 public K firstKey() { 2828 synchronized (mutex) {return sm.firstKey();} 2829 } 2830 public K lastKey() { 2831 synchronized (mutex) {return sm.lastKey();} 2832 } 2833 } 2834 2835 /** 2836 * Returns a synchronized (thread-safe) navigable map backed by the 2837 * specified navigable map. In order to guarantee serial access, it is 2838 * critical that <strong>all</strong> access to the backing navigable map is 2839 * accomplished through the returned navigable map (or its views).<p> 2840 * 2841 * It is imperative that the user manually synchronize on the returned 2842 * navigable map when iterating over any of its collection views, or the 2843 * collections views of any of its {@code subMap}, {@code headMap} or 2844 * {@code tailMap} views. 2845 * <pre> 2846 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap()); 2847 * ... 2848 * Set s = m.keySet(); // Needn't be in synchronized block 2849 * ... 2850 * synchronized (m) { // Synchronizing on m, not s! 2851 * Iterator i = s.iterator(); // Must be in synchronized block 2852 * while (i.hasNext()) 2853 * foo(i.next()); 2854 * } 2855 * </pre> 2856 * or: 2857 * <pre> 2858 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap()); 2859 * NavigableMap m2 = m.subMap(foo, true, bar, false); 2860 * ... 2861 * Set s2 = m2.keySet(); // Needn't be in synchronized block 2862 * ... 2863 * synchronized (m) { // Synchronizing on m, not m2 or s2! 2864 * Iterator i = s.iterator(); // Must be in synchronized block 2865 * while (i.hasNext()) 2866 * foo(i.next()); 2867 * } 2868 * </pre> 2869 * Failure to follow this advice may result in non-deterministic behavior. 2870 * 2871 * <p>The returned navigable map will be serializable if the specified 2872 * navigable map is serializable. 2873 * 2874 * @param <K> the class of the map keys 2875 * @param <V> the class of the map values 2876 * @param m the navigable map to be "wrapped" in a synchronized navigable 2877 * map 2878 * @return a synchronized view of the specified navigable map. 2879 * @since 1.8 2880 */ 2881 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) { 2882 return new SynchronizedNavigableMap<>(m); 2883 } 2884 2885 /** 2886 * A synchronized NavigableMap. 2887 * 2888 * @serial include 2889 */ 2890 static class SynchronizedNavigableMap<K,V> 2891 extends SynchronizedSortedMap<K,V> 2892 implements NavigableMap<K,V> 2893 { 2894 private static final long serialVersionUID = 699392247599746807L; 2895 2896 private final NavigableMap<K,V> nm; 2897 2898 SynchronizedNavigableMap(NavigableMap<K,V> m) { 2899 super(m); 2900 nm = m; 2901 } 2902 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) { 2903 super(m, mutex); 2904 nm = m; 2905 } 2906 2907 public Entry<K, V> lowerEntry(K key) 2908 { synchronized (mutex) { return nm.lowerEntry(key); } } 2909 public K lowerKey(K key) 2910 { synchronized (mutex) { return nm.lowerKey(key); } } 2911 public Entry<K, V> floorEntry(K key) 2912 { synchronized (mutex) { return nm.floorEntry(key); } } 2913 public K floorKey(K key) 2914 { synchronized (mutex) { return nm.floorKey(key); } } 2915 public Entry<K, V> ceilingEntry(K key) 2916 { synchronized (mutex) { return nm.ceilingEntry(key); } } 2917 public K ceilingKey(K key) 2918 { synchronized (mutex) { return nm.ceilingKey(key); } } 2919 public Entry<K, V> higherEntry(K key) 2920 { synchronized (mutex) { return nm.higherEntry(key); } } 2921 public K higherKey(K key) 2922 { synchronized (mutex) { return nm.higherKey(key); } } 2923 public Entry<K, V> firstEntry() 2924 { synchronized (mutex) { return nm.firstEntry(); } } 2925 public Entry<K, V> lastEntry() 2926 { synchronized (mutex) { return nm.lastEntry(); } } 2927 public Entry<K, V> pollFirstEntry() 2928 { synchronized (mutex) { return nm.pollFirstEntry(); } } 2929 public Entry<K, V> pollLastEntry() 2930 { synchronized (mutex) { return nm.pollLastEntry(); } } 2931 2932 public NavigableMap<K, V> descendingMap() { 2933 synchronized (mutex) { 2934 return 2935 new SynchronizedNavigableMap<>(nm.descendingMap(), mutex); 2936 } 2937 } 2938 2939 public NavigableSet<K> keySet() { 2940 return navigableKeySet(); 2941 } 2942 2943 public NavigableSet<K> navigableKeySet() { 2944 synchronized (mutex) { 2945 return new SynchronizedNavigableSet<>(nm.navigableKeySet(), mutex); 2946 } 2947 } 2948 2949 public NavigableSet<K> descendingKeySet() { 2950 synchronized (mutex) { 2951 return new SynchronizedNavigableSet<>(nm.descendingKeySet(), mutex); 2952 } 2953 } 2954 2955 2956 public SortedMap<K,V> subMap(K fromKey, K toKey) { 2957 synchronized (mutex) { 2958 return new SynchronizedNavigableMap<>( 2959 nm.subMap(fromKey, true, toKey, false), mutex); 2960 } 2961 } 2962 public SortedMap<K,V> headMap(K toKey) { 2963 synchronized (mutex) { 2964 return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex); 2965 } 2966 } 2967 public SortedMap<K,V> tailMap(K fromKey) { 2968 synchronized (mutex) { 2969 return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex); 2970 } 2971 } 2972 2973 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 2974 synchronized (mutex) { 2975 return new SynchronizedNavigableMap<>( 2976 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex); 2977 } 2978 } 2979 2980 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) { 2981 synchronized (mutex) { 2982 return new SynchronizedNavigableMap<>( 2983 nm.headMap(toKey, inclusive), mutex); 2984 } 2985 } 2986 2987 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) { 2988 synchronized (mutex) { 2989 return new SynchronizedNavigableMap<>( 2990 nm.tailMap(fromKey, inclusive), mutex); 2991 } 2992 } 2993 } 2994 2995 // Dynamically typesafe collection wrappers 2996 2997 /** 2998 * Returns a dynamically typesafe view of the specified collection. 2999 * Any attempt to insert an element of the wrong type will result in an 3000 * immediate {@link ClassCastException}. Assuming a collection 3001 * contains no incorrectly typed elements prior to the time a 3002 * dynamically typesafe view is generated, and that all subsequent 3003 * access to the collection takes place through the view, it is 3004 * <i>guaranteed</i> that the collection cannot contain an incorrectly 3005 * typed element. 3006 * 3007 * <p>The generics mechanism in the language provides compile-time 3008 * (static) type checking, but it is possible to defeat this mechanism 3009 * with unchecked casts. Usually this is not a problem, as the compiler 3010 * issues warnings on all such unchecked operations. There are, however, 3011 * times when static type checking alone is not sufficient. For example, 3012 * suppose a collection is passed to a third-party library and it is 3013 * imperative that the library code not corrupt the collection by 3014 * inserting an element of the wrong type. 3015 * 3016 * <p>Another use of dynamically typesafe views is debugging. Suppose a 3017 * program fails with a {@code ClassCastException}, indicating that an 3018 * incorrectly typed element was put into a parameterized collection. 3019 * Unfortunately, the exception can occur at any time after the erroneous 3020 * element is inserted, so it typically provides little or no information 3021 * as to the real source of the problem. If the problem is reproducible, 3022 * one can quickly determine its source by temporarily modifying the 3023 * program to wrap the collection with a dynamically typesafe view. 3024 * For example, this declaration: 3025 * <pre> {@code 3026 * Collection<String> c = new HashSet<>(); 3027 * }</pre> 3028 * may be replaced temporarily by this one: 3029 * <pre> {@code 3030 * Collection<String> c = Collections.checkedCollection( 3031 * new HashSet<>(), String.class); 3032 * }</pre> 3033 * Running the program again will cause it to fail at the point where 3034 * an incorrectly typed element is inserted into the collection, clearly 3035 * identifying the source of the problem. Once the problem is fixed, the 3036 * modified declaration may be reverted back to the original. 3037 * 3038 * <p>The returned collection does <i>not</i> pass the hashCode and equals 3039 * operations through to the backing collection, but relies on 3040 * {@code Object}'s {@code equals} and {@code hashCode} methods. This 3041 * is necessary to preserve the contracts of these operations in the case 3042 * that the backing collection is a set or a list. 3043 * 3044 * <p>The returned collection will be serializable if the specified 3045 * collection is serializable. 3046 * 3047 * <p>Since {@code null} is considered to be a value of any reference 3048 * type, the returned collection permits insertion of null elements 3049 * whenever the backing collection does. 3050 * 3051 * @param <E> the class of the objects in the collection 3052 * @param c the collection for which a dynamically typesafe view is to be 3053 * returned 3054 * @param type the type of element that {@code c} is permitted to hold 3055 * @return a dynamically typesafe view of the specified collection 3056 * @since 1.5 3057 */ 3058 public static <E> Collection<E> checkedCollection(Collection<E> c, 3059 Class<E> type) { 3060 return new CheckedCollection<>(c, type); 3061 } 3062 3063 @SuppressWarnings("unchecked") 3064 static <T> T[] zeroLengthArray(Class<T> type) { 3065 return (T[]) Array.newInstance(type, 0); 3066 } 3067 3068 /** 3069 * @serial include 3070 */ 3071 static class CheckedCollection<E> implements Collection<E>, Serializable { 3072 private static final long serialVersionUID = 1578914078182001775L; 3073 3074 final Collection<E> c; 3075 final Class<E> type; 3076 3077 @SuppressWarnings("unchecked") 3078 E typeCheck(Object o) { 3079 if (o != null && !type.isInstance(o)) 3080 throw new ClassCastException(badElementMsg(o)); 3081 return (E) o; 3082 } 3083 3084 private String badElementMsg(Object o) { 3085 return "Attempt to insert " + o.getClass() + 3086 " element into collection with element type " + type; 3087 } 3088 3089 CheckedCollection(Collection<E> c, Class<E> type) { 3090 this.c = Objects.requireNonNull(c, "c"); 3091 this.type = Objects.requireNonNull(type, "type"); 3092 } 3093 3094 public int size() { return c.size(); } 3095 public boolean isEmpty() { return c.isEmpty(); } 3096 public boolean contains(Object o) { return c.contains(o); } 3097 public Object[] toArray() { return c.toArray(); } 3098 public <T> T[] toArray(T[] a) { return c.toArray(a); } 3099 public String toString() { return c.toString(); } 3100 public boolean remove(Object o) { return c.remove(o); } 3101 public void clear() { c.clear(); } 3102 3103 public boolean containsAll(Collection<?> coll) { 3104 return c.containsAll(coll); 3105 } 3106 public boolean removeAll(Collection<?> coll) { 3107 return c.removeAll(coll); 3108 } 3109 public boolean retainAll(Collection<?> coll) { 3110 return c.retainAll(coll); 3111 } 3112 3113 public Iterator<E> iterator() { 3114 // JDK-6363904 - unwrapped iterator could be typecast to 3115 // ListIterator with unsafe set() 3116 final Iterator<E> it = c.iterator(); 3117 return new Iterator<E>() { 3118 public boolean hasNext() { return it.hasNext(); } 3119 public E next() { return it.next(); } 3120 public void remove() { it.remove(); }}; 3121 // Android-note: Should we delegate to it for forEachRemaining ? 3122 } 3123 3124 public boolean add(E e) { return c.add(typeCheck(e)); } 3125 3126 private E[] zeroLengthElementArray; // Lazily initialized 3127 3128 private E[] zeroLengthElementArray() { 3129 return zeroLengthElementArray != null ? zeroLengthElementArray : 3130 (zeroLengthElementArray = zeroLengthArray(type)); 3131 } 3132 3133 @SuppressWarnings("unchecked") 3134 Collection<E> checkedCopyOf(Collection<? extends E> coll) { 3135 Object[] a; 3136 try { 3137 E[] z = zeroLengthElementArray(); 3138 a = coll.toArray(z); 3139 // Defend against coll violating the toArray contract 3140 if (a.getClass() != z.getClass()) 3141 a = Arrays.copyOf(a, a.length, z.getClass()); 3142 } catch (ArrayStoreException ignore) { 3143 // To get better and consistent diagnostics, 3144 // we call typeCheck explicitly on each element. 3145 // We call clone() to defend against coll retaining a 3146 // reference to the returned array and storing a bad 3147 // element into it after it has been type checked. 3148 a = coll.toArray().clone(); 3149 for (Object o : a) 3150 typeCheck(o); 3151 } 3152 // A slight abuse of the type system, but safe here. 3153 return (Collection<E>) Arrays.asList(a); 3154 } 3155 3156 public boolean addAll(Collection<? extends E> coll) { 3157 // Doing things this way insulates us from concurrent changes 3158 // in the contents of coll and provides all-or-nothing 3159 // semantics (which we wouldn't get if we type-checked each 3160 // element as we added it) 3161 return c.addAll(checkedCopyOf(coll)); 3162 } 3163 3164 // Override default methods in Collection 3165 @Override 3166 public void forEach(Consumer<? super E> action) {c.forEach(action);} 3167 @Override 3168 public boolean removeIf(Predicate<? super E> filter) { 3169 return c.removeIf(filter); 3170 } 3171 @Override 3172 public Spliterator<E> spliterator() {return c.spliterator();} 3173 @Override 3174 public Stream<E> stream() {return c.stream();} 3175 @Override 3176 public Stream<E> parallelStream() {return c.parallelStream();} 3177 } 3178 3179 /** 3180 * Returns a dynamically typesafe view of the specified queue. 3181 * Any attempt to insert an element of the wrong type will result in 3182 * an immediate {@link ClassCastException}. Assuming a queue contains 3183 * no incorrectly typed elements prior to the time a dynamically typesafe 3184 * view is generated, and that all subsequent access to the queue 3185 * takes place through the view, it is <i>guaranteed</i> that the 3186 * queue cannot contain an incorrectly typed element. 3187 * 3188 * <p>A discussion of the use of dynamically typesafe views may be 3189 * found in the documentation for the {@link #checkedCollection 3190 * checkedCollection} method. 3191 * 3192 * <p>The returned queue will be serializable if the specified queue 3193 * is serializable. 3194 * 3195 * <p>Since {@code null} is considered to be a value of any reference 3196 * type, the returned queue permits insertion of {@code null} elements 3197 * whenever the backing queue does. 3198 * 3199 * @param <E> the class of the objects in the queue 3200 * @param queue the queue for which a dynamically typesafe view is to be 3201 * returned 3202 * @param type the type of element that {@code queue} is permitted to hold 3203 * @return a dynamically typesafe view of the specified queue 3204 * @since 1.8 3205 */ 3206 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) { 3207 return new CheckedQueue<>(queue, type); 3208 } 3209 3210 /** 3211 * @serial include 3212 */ 3213 static class CheckedQueue<E> 3214 extends CheckedCollection<E> 3215 implements Queue<E>, Serializable 3216 { 3217 private static final long serialVersionUID = 1433151992604707767L; 3218 final Queue<E> queue; 3219 3220 CheckedQueue(Queue<E> queue, Class<E> elementType) { 3221 super(queue, elementType); 3222 this.queue = queue; 3223 } 3224 3225 public E element() {return queue.element();} 3226 public boolean equals(Object o) {return o == this || c.equals(o);} 3227 public int hashCode() {return c.hashCode();} 3228 public E peek() {return queue.peek();} 3229 public E poll() {return queue.poll();} 3230 public E remove() {return queue.remove();} 3231 public boolean offer(E e) {return queue.offer(typeCheck(e));} 3232 } 3233 3234 /** 3235 * Returns a dynamically typesafe view of the specified set. 3236 * Any attempt to insert an element of the wrong type will result in 3237 * an immediate {@link ClassCastException}. Assuming a set contains 3238 * no incorrectly typed elements prior to the time a dynamically typesafe 3239 * view is generated, and that all subsequent access to the set 3240 * takes place through the view, it is <i>guaranteed</i> that the 3241 * set cannot contain an incorrectly typed element. 3242 * 3243 * <p>A discussion of the use of dynamically typesafe views may be 3244 * found in the documentation for the {@link #checkedCollection 3245 * checkedCollection} method. 3246 * 3247 * <p>The returned set will be serializable if the specified set is 3248 * serializable. 3249 * 3250 * <p>Since {@code null} is considered to be a value of any reference 3251 * type, the returned set permits insertion of null elements whenever 3252 * the backing set does. 3253 * 3254 * @param <E> the class of the objects in the set 3255 * @param s the set for which a dynamically typesafe view is to be 3256 * returned 3257 * @param type the type of element that {@code s} is permitted to hold 3258 * @return a dynamically typesafe view of the specified set 3259 * @since 1.5 3260 */ 3261 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) { 3262 return new CheckedSet<>(s, type); 3263 } 3264 3265 /** 3266 * @serial include 3267 */ 3268 static class CheckedSet<E> extends CheckedCollection<E> 3269 implements Set<E>, Serializable 3270 { 3271 private static final long serialVersionUID = 4694047833775013803L; 3272 3273 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); } 3274 3275 public boolean equals(Object o) { return o == this || c.equals(o); } 3276 public int hashCode() { return c.hashCode(); } 3277 } 3278 3279 /** 3280 * Returns a dynamically typesafe view of the specified sorted set. 3281 * Any attempt to insert an element of the wrong type will result in an 3282 * immediate {@link ClassCastException}. Assuming a sorted set 3283 * contains no incorrectly typed elements prior to the time a 3284 * dynamically typesafe view is generated, and that all subsequent 3285 * access to the sorted set takes place through the view, it is 3286 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly 3287 * typed element. 3288 * 3289 * <p>A discussion of the use of dynamically typesafe views may be 3290 * found in the documentation for the {@link #checkedCollection 3291 * checkedCollection} method. 3292 * 3293 * <p>The returned sorted set will be serializable if the specified sorted 3294 * set is serializable. 3295 * 3296 * <p>Since {@code null} is considered to be a value of any reference 3297 * type, the returned sorted set permits insertion of null elements 3298 * whenever the backing sorted set does. 3299 * 3300 * @param <E> the class of the objects in the set 3301 * @param s the sorted set for which a dynamically typesafe view is to be 3302 * returned 3303 * @param type the type of element that {@code s} is permitted to hold 3304 * @return a dynamically typesafe view of the specified sorted set 3305 * @since 1.5 3306 */ 3307 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s, 3308 Class<E> type) { 3309 return new CheckedSortedSet<>(s, type); 3310 } 3311 3312 /** 3313 * @serial include 3314 */ 3315 static class CheckedSortedSet<E> extends CheckedSet<E> 3316 implements SortedSet<E>, Serializable 3317 { 3318 private static final long serialVersionUID = 1599911165492914959L; 3319 3320 private final SortedSet<E> ss; 3321 3322 CheckedSortedSet(SortedSet<E> s, Class<E> type) { 3323 super(s, type); 3324 ss = s; 3325 } 3326 3327 public Comparator<? super E> comparator() { return ss.comparator(); } 3328 public E first() { return ss.first(); } 3329 public E last() { return ss.last(); } 3330 3331 public SortedSet<E> subSet(E fromElement, E toElement) { 3332 return checkedSortedSet(ss.subSet(fromElement,toElement), type); 3333 } 3334 public SortedSet<E> headSet(E toElement) { 3335 return checkedSortedSet(ss.headSet(toElement), type); 3336 } 3337 public SortedSet<E> tailSet(E fromElement) { 3338 return checkedSortedSet(ss.tailSet(fromElement), type); 3339 } 3340 } 3341 3342/** 3343 * Returns a dynamically typesafe view of the specified navigable set. 3344 * Any attempt to insert an element of the wrong type will result in an 3345 * immediate {@link ClassCastException}. Assuming a navigable set 3346 * contains no incorrectly typed elements prior to the time a 3347 * dynamically typesafe view is generated, and that all subsequent 3348 * access to the navigable set takes place through the view, it is 3349 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly 3350 * typed element. 3351 * 3352 * <p>A discussion of the use of dynamically typesafe views may be 3353 * found in the documentation for the {@link #checkedCollection 3354 * checkedCollection} method. 3355 * 3356 * <p>The returned navigable set will be serializable if the specified 3357 * navigable set is serializable. 3358 * 3359 * <p>Since {@code null} is considered to be a value of any reference 3360 * type, the returned navigable set permits insertion of null elements 3361 * whenever the backing sorted set does. 3362 * 3363 * @param <E> the class of the objects in the set 3364 * @param s the navigable set for which a dynamically typesafe view is to be 3365 * returned 3366 * @param type the type of element that {@code s} is permitted to hold 3367 * @return a dynamically typesafe view of the specified navigable set 3368 * @since 1.8 3369 */ 3370 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s, 3371 Class<E> type) { 3372 return new CheckedNavigableSet<>(s, type); 3373 } 3374 3375 /** 3376 * @serial include 3377 */ 3378 static class CheckedNavigableSet<E> extends CheckedSortedSet<E> 3379 implements NavigableSet<E>, Serializable 3380 { 3381 private static final long serialVersionUID = -5429120189805438922L; 3382 3383 private final NavigableSet<E> ns; 3384 3385 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) { 3386 super(s, type); 3387 ns = s; 3388 } 3389 3390 public E lower(E e) { return ns.lower(e); } 3391 public E floor(E e) { return ns.floor(e); } 3392 public E ceiling(E e) { return ns.ceiling(e); } 3393 public E higher(E e) { return ns.higher(e); } 3394 public E pollFirst() { return ns.pollFirst(); } 3395 public E pollLast() {return ns.pollLast(); } 3396 public NavigableSet<E> descendingSet() 3397 { return checkedNavigableSet(ns.descendingSet(), type); } 3398 public Iterator<E> descendingIterator() 3399 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); } 3400 3401 public NavigableSet<E> subSet(E fromElement, E toElement) { 3402 return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type); 3403 } 3404 public NavigableSet<E> headSet(E toElement) { 3405 return checkedNavigableSet(ns.headSet(toElement, false), type); 3406 } 3407 public NavigableSet<E> tailSet(E fromElement) { 3408 return checkedNavigableSet(ns.tailSet(fromElement, true), type); 3409 } 3410 3411 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 3412 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type); 3413 } 3414 3415 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 3416 return checkedNavigableSet(ns.headSet(toElement, inclusive), type); 3417 } 3418 3419 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 3420 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type); 3421 } 3422 } 3423 3424 /** 3425 * Returns a dynamically typesafe view of the specified list. 3426 * Any attempt to insert an element of the wrong type will result in 3427 * an immediate {@link ClassCastException}. Assuming a list contains 3428 * no incorrectly typed elements prior to the time a dynamically typesafe 3429 * view is generated, and that all subsequent access to the list 3430 * takes place through the view, it is <i>guaranteed</i> that the 3431 * list cannot contain an incorrectly typed element. 3432 * 3433 * <p>A discussion of the use of dynamically typesafe views may be 3434 * found in the documentation for the {@link #checkedCollection 3435 * checkedCollection} method. 3436 * 3437 * <p>The returned list will be serializable if the specified list 3438 * is serializable. 3439 * 3440 * <p>Since {@code null} is considered to be a value of any reference 3441 * type, the returned list permits insertion of null elements whenever 3442 * the backing list does. 3443 * 3444 * @param <E> the class of the objects in the list 3445 * @param list the list for which a dynamically typesafe view is to be 3446 * returned 3447 * @param type the type of element that {@code list} is permitted to hold 3448 * @return a dynamically typesafe view of the specified list 3449 * @since 1.5 3450 */ 3451 public static <E> List<E> checkedList(List<E> list, Class<E> type) { 3452 return (list instanceof RandomAccess ? 3453 new CheckedRandomAccessList<>(list, type) : 3454 new CheckedList<>(list, type)); 3455 } 3456 3457 /** 3458 * @serial include 3459 */ 3460 static class CheckedList<E> 3461 extends CheckedCollection<E> 3462 implements List<E> 3463 { 3464 private static final long serialVersionUID = 65247728283967356L; 3465 final List<E> list; 3466 3467 CheckedList(List<E> list, Class<E> type) { 3468 super(list, type); 3469 this.list = list; 3470 } 3471 3472 public boolean equals(Object o) { return o == this || list.equals(o); } 3473 public int hashCode() { return list.hashCode(); } 3474 public E get(int index) { return list.get(index); } 3475 public E remove(int index) { return list.remove(index); } 3476 public int indexOf(Object o) { return list.indexOf(o); } 3477 public int lastIndexOf(Object o) { return list.lastIndexOf(o); } 3478 3479 public E set(int index, E element) { 3480 return list.set(index, typeCheck(element)); 3481 } 3482 3483 public void add(int index, E element) { 3484 list.add(index, typeCheck(element)); 3485 } 3486 3487 public boolean addAll(int index, Collection<? extends E> c) { 3488 return list.addAll(index, checkedCopyOf(c)); 3489 } 3490 public ListIterator<E> listIterator() { return listIterator(0); } 3491 3492 public ListIterator<E> listIterator(final int index) { 3493 final ListIterator<E> i = list.listIterator(index); 3494 3495 return new ListIterator<E>() { 3496 public boolean hasNext() { return i.hasNext(); } 3497 public E next() { return i.next(); } 3498 public boolean hasPrevious() { return i.hasPrevious(); } 3499 public E previous() { return i.previous(); } 3500 public int nextIndex() { return i.nextIndex(); } 3501 public int previousIndex() { return i.previousIndex(); } 3502 public void remove() { i.remove(); } 3503 3504 public void set(E e) { 3505 i.set(typeCheck(e)); 3506 } 3507 3508 public void add(E e) { 3509 i.add(typeCheck(e)); 3510 } 3511 3512 @Override 3513 public void forEachRemaining(Consumer<? super E> action) { 3514 i.forEachRemaining(action); 3515 } 3516 }; 3517 } 3518 3519 public List<E> subList(int fromIndex, int toIndex) { 3520 return new CheckedList<>(list.subList(fromIndex, toIndex), type); 3521 } 3522 3523 /** 3524 * {@inheritDoc} 3525 * 3526 * @throws ClassCastException if the class of an element returned by the 3527 * operator prevents it from being added to this collection. The 3528 * exception may be thrown after some elements of the list have 3529 * already been replaced. 3530 */ 3531 @Override 3532 public void replaceAll(UnaryOperator<E> operator) { 3533 Objects.requireNonNull(operator); 3534 list.replaceAll(e -> typeCheck(operator.apply(e))); 3535 } 3536 3537 @Override 3538 public void sort(Comparator<? super E> c) { 3539 list.sort(c); 3540 } 3541 } 3542 3543 /** 3544 * @serial include 3545 */ 3546 static class CheckedRandomAccessList<E> extends CheckedList<E> 3547 implements RandomAccess 3548 { 3549 private static final long serialVersionUID = 1638200125423088369L; 3550 3551 CheckedRandomAccessList(List<E> list, Class<E> type) { 3552 super(list, type); 3553 } 3554 3555 public List<E> subList(int fromIndex, int toIndex) { 3556 return new CheckedRandomAccessList<>( 3557 list.subList(fromIndex, toIndex), type); 3558 } 3559 } 3560 3561 /** 3562 * Returns a dynamically typesafe view of the specified map. 3563 * Any attempt to insert a mapping whose key or value have the wrong 3564 * type will result in an immediate {@link ClassCastException}. 3565 * Similarly, any attempt to modify the value currently associated with 3566 * a key will result in an immediate {@link ClassCastException}, 3567 * whether the modification is attempted directly through the map 3568 * itself, or through a {@link Map.Entry} instance obtained from the 3569 * map's {@link Map#entrySet() entry set} view. 3570 * 3571 * <p>Assuming a map contains no incorrectly typed keys or values 3572 * prior to the time a dynamically typesafe view is generated, and 3573 * that all subsequent access to the map takes place through the view 3574 * (or one of its collection views), it is <i>guaranteed</i> that the 3575 * map cannot contain an incorrectly typed key or value. 3576 * 3577 * <p>A discussion of the use of dynamically typesafe views may be 3578 * found in the documentation for the {@link #checkedCollection 3579 * checkedCollection} method. 3580 * 3581 * <p>The returned map will be serializable if the specified map is 3582 * serializable. 3583 * 3584 * <p>Since {@code null} is considered to be a value of any reference 3585 * type, the returned map permits insertion of null keys or values 3586 * whenever the backing map does. 3587 * 3588 * @param <K> the class of the map keys 3589 * @param <V> the class of the map values 3590 * @param m the map for which a dynamically typesafe view is to be 3591 * returned 3592 * @param keyType the type of key that {@code m} is permitted to hold 3593 * @param valueType the type of value that {@code m} is permitted to hold 3594 * @return a dynamically typesafe view of the specified map 3595 * @since 1.5 3596 */ 3597 public static <K, V> Map<K, V> checkedMap(Map<K, V> m, 3598 Class<K> keyType, 3599 Class<V> valueType) { 3600 return new CheckedMap<>(m, keyType, valueType); 3601 } 3602 3603 3604 /** 3605 * @serial include 3606 */ 3607 private static class CheckedMap<K,V> 3608 implements Map<K,V>, Serializable 3609 { 3610 private static final long serialVersionUID = 5742860141034234728L; 3611 3612 private final Map<K, V> m; 3613 final Class<K> keyType; 3614 final Class<V> valueType; 3615 3616 private void typeCheck(Object key, Object value) { 3617 if (key != null && !keyType.isInstance(key)) 3618 throw new ClassCastException(badKeyMsg(key)); 3619 3620 if (value != null && !valueType.isInstance(value)) 3621 throw new ClassCastException(badValueMsg(value)); 3622 } 3623 3624 private BiFunction<? super K, ? super V, ? extends V> typeCheck( 3625 BiFunction<? super K, ? super V, ? extends V> func) { 3626 Objects.requireNonNull(func); 3627 return (k, v) -> { 3628 V newValue = func.apply(k, v); 3629 typeCheck(k, newValue); 3630 return newValue; 3631 }; 3632 } 3633 3634 private String badKeyMsg(Object key) { 3635 return "Attempt to insert " + key.getClass() + 3636 " key into map with key type " + keyType; 3637 } 3638 3639 private String badValueMsg(Object value) { 3640 return "Attempt to insert " + value.getClass() + 3641 " value into map with value type " + valueType; 3642 } 3643 3644 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) { 3645 this.m = Objects.requireNonNull(m); 3646 this.keyType = Objects.requireNonNull(keyType); 3647 this.valueType = Objects.requireNonNull(valueType); 3648 } 3649 3650 public int size() { return m.size(); } 3651 public boolean isEmpty() { return m.isEmpty(); } 3652 public boolean containsKey(Object key) { return m.containsKey(key); } 3653 public boolean containsValue(Object v) { return m.containsValue(v); } 3654 public V get(Object key) { return m.get(key); } 3655 public V remove(Object key) { return m.remove(key); } 3656 public void clear() { m.clear(); } 3657 public Set<K> keySet() { return m.keySet(); } 3658 public Collection<V> values() { return m.values(); } 3659 public boolean equals(Object o) { return o == this || m.equals(o); } 3660 public int hashCode() { return m.hashCode(); } 3661 public String toString() { return m.toString(); } 3662 3663 public V put(K key, V value) { 3664 typeCheck(key, value); 3665 return m.put(key, value); 3666 } 3667 3668 @SuppressWarnings("unchecked") 3669 public void putAll(Map<? extends K, ? extends V> t) { 3670 // Satisfy the following goals: 3671 // - good diagnostics in case of type mismatch 3672 // - all-or-nothing semantics 3673 // - protection from malicious t 3674 // - correct behavior if t is a concurrent map 3675 Object[] entries = t.entrySet().toArray(); 3676 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length); 3677 for (Object o : entries) { 3678 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3679 Object k = e.getKey(); 3680 Object v = e.getValue(); 3681 typeCheck(k, v); 3682 checked.add( 3683 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v)); 3684 } 3685 for (Map.Entry<K,V> e : checked) 3686 m.put(e.getKey(), e.getValue()); 3687 } 3688 3689 private transient Set<Map.Entry<K,V>> entrySet; 3690 3691 public Set<Map.Entry<K,V>> entrySet() { 3692 if (entrySet==null) 3693 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType); 3694 return entrySet; 3695 } 3696 3697 // Override default methods in Map 3698 @Override 3699 public void forEach(BiConsumer<? super K, ? super V> action) { 3700 m.forEach(action); 3701 } 3702 3703 @Override 3704 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 3705 m.replaceAll(typeCheck(function)); 3706 } 3707 3708 @Override 3709 public V putIfAbsent(K key, V value) { 3710 typeCheck(key, value); 3711 return m.putIfAbsent(key, value); 3712 } 3713 3714 @Override 3715 public boolean remove(Object key, Object value) { 3716 return m.remove(key, value); 3717 } 3718 3719 @Override 3720 public boolean replace(K key, V oldValue, V newValue) { 3721 typeCheck(key, newValue); 3722 return m.replace(key, oldValue, newValue); 3723 } 3724 3725 @Override 3726 public V replace(K key, V value) { 3727 typeCheck(key, value); 3728 return m.replace(key, value); 3729 } 3730 3731 @Override 3732 public V computeIfAbsent(K key, 3733 Function<? super K, ? extends V> mappingFunction) { 3734 Objects.requireNonNull(mappingFunction); 3735 return m.computeIfAbsent(key, k -> { 3736 V value = mappingFunction.apply(k); 3737 typeCheck(k, value); 3738 return value; 3739 }); 3740 } 3741 3742 @Override 3743 public V computeIfPresent(K key, 3744 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3745 return m.computeIfPresent(key, typeCheck(remappingFunction)); 3746 } 3747 3748 @Override 3749 public V compute(K key, 3750 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3751 return m.compute(key, typeCheck(remappingFunction)); 3752 } 3753 3754 @Override 3755 public V merge(K key, V value, 3756 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 3757 Objects.requireNonNull(remappingFunction); 3758 return m.merge(key, value, (v1, v2) -> { 3759 V newValue = remappingFunction.apply(v1, v2); 3760 typeCheck(null, newValue); 3761 return newValue; 3762 }); 3763 } 3764 3765 /** 3766 * We need this class in addition to CheckedSet as Map.Entry permits 3767 * modification of the backing Map via the setValue operation. This 3768 * class is subtle: there are many possible attacks that must be 3769 * thwarted. 3770 * 3771 * @serial exclude 3772 */ 3773 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> { 3774 private final Set<Map.Entry<K,V>> s; 3775 private final Class<V> valueType; 3776 3777 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) { 3778 this.s = s; 3779 this.valueType = valueType; 3780 } 3781 3782 public int size() { return s.size(); } 3783 public boolean isEmpty() { return s.isEmpty(); } 3784 public String toString() { return s.toString(); } 3785 public int hashCode() { return s.hashCode(); } 3786 public void clear() { s.clear(); } 3787 3788 public boolean add(Map.Entry<K, V> e) { 3789 throw new UnsupportedOperationException(); 3790 } 3791 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) { 3792 throw new UnsupportedOperationException(); 3793 } 3794 3795 public Iterator<Map.Entry<K,V>> iterator() { 3796 final Iterator<Map.Entry<K, V>> i = s.iterator(); 3797 final Class<V> valueType = this.valueType; 3798 3799 return new Iterator<Map.Entry<K,V>>() { 3800 public boolean hasNext() { return i.hasNext(); } 3801 public void remove() { i.remove(); } 3802 3803 public Map.Entry<K,V> next() { 3804 return checkedEntry(i.next(), valueType); 3805 } 3806 // Android-note: forEachRemaining is missing checks. 3807 }; 3808 } 3809 3810 @SuppressWarnings("unchecked") 3811 public Object[] toArray() { 3812 Object[] source = s.toArray(); 3813 3814 /* 3815 * Ensure that we don't get an ArrayStoreException even if 3816 * s.toArray returns an array of something other than Object 3817 */ 3818 Object[] dest = (CheckedEntry.class.isInstance( 3819 source.getClass().getComponentType()) ? source : 3820 new Object[source.length]); 3821 3822 for (int i = 0; i < source.length; i++) 3823 dest[i] = checkedEntry((Map.Entry<K,V>)source[i], 3824 valueType); 3825 return dest; 3826 } 3827 3828 @SuppressWarnings("unchecked") 3829 public <T> T[] toArray(T[] a) { 3830 // We don't pass a to s.toArray, to avoid window of 3831 // vulnerability wherein an unscrupulous multithreaded client 3832 // could get his hands on raw (unwrapped) Entries from s. 3833 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); 3834 3835 for (int i=0; i<arr.length; i++) 3836 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i], 3837 valueType); 3838 if (arr.length > a.length) 3839 return arr; 3840 3841 System.arraycopy(arr, 0, a, 0, arr.length); 3842 if (a.length > arr.length) 3843 a[arr.length] = null; 3844 return a; 3845 } 3846 3847 /** 3848 * This method is overridden to protect the backing set against 3849 * an object with a nefarious equals function that senses 3850 * that the equality-candidate is Map.Entry and calls its 3851 * setValue method. 3852 */ 3853 public boolean contains(Object o) { 3854 if (!(o instanceof Map.Entry)) 3855 return false; 3856 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3857 return s.contains( 3858 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType)); 3859 } 3860 3861 /** 3862 * The bulk collection methods are overridden to protect 3863 * against an unscrupulous collection whose contains(Object o) 3864 * method senses when o is a Map.Entry, and calls o.setValue. 3865 */ 3866 public boolean containsAll(Collection<?> c) { 3867 for (Object o : c) 3868 if (!contains(o)) // Invokes safe contains() above 3869 return false; 3870 return true; 3871 } 3872 3873 public boolean remove(Object o) { 3874 if (!(o instanceof Map.Entry)) 3875 return false; 3876 return s.remove(new AbstractMap.SimpleImmutableEntry 3877 <>((Map.Entry<?,?>)o)); 3878 } 3879 3880 public boolean removeAll(Collection<?> c) { 3881 return batchRemove(c, false); 3882 } 3883 public boolean retainAll(Collection<?> c) { 3884 return batchRemove(c, true); 3885 } 3886 private boolean batchRemove(Collection<?> c, boolean complement) { 3887 Objects.requireNonNull(c); 3888 boolean modified = false; 3889 Iterator<Map.Entry<K,V>> it = iterator(); 3890 while (it.hasNext()) { 3891 if (c.contains(it.next()) != complement) { 3892 it.remove(); 3893 modified = true; 3894 } 3895 } 3896 return modified; 3897 } 3898 3899 public boolean equals(Object o) { 3900 if (o == this) 3901 return true; 3902 if (!(o instanceof Set)) 3903 return false; 3904 Set<?> that = (Set<?>) o; 3905 return that.size() == s.size() 3906 && containsAll(that); // Invokes safe containsAll() above 3907 } 3908 3909 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e, 3910 Class<T> valueType) { 3911 return new CheckedEntry<>(e, valueType); 3912 } 3913 3914 /** 3915 * This "wrapper class" serves two purposes: it prevents 3916 * the client from modifying the backing Map, by short-circuiting 3917 * the setValue method, and it protects the backing Map against 3918 * an ill-behaved Map.Entry that attempts to modify another 3919 * Map.Entry when asked to perform an equality check. 3920 */ 3921 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> { 3922 private final Map.Entry<K, V> e; 3923 private final Class<T> valueType; 3924 3925 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) { 3926 this.e = Objects.requireNonNull(e); 3927 this.valueType = Objects.requireNonNull(valueType); 3928 } 3929 3930 public K getKey() { return e.getKey(); } 3931 public V getValue() { return e.getValue(); } 3932 public int hashCode() { return e.hashCode(); } 3933 public String toString() { return e.toString(); } 3934 3935 public V setValue(V value) { 3936 if (value != null && !valueType.isInstance(value)) 3937 throw new ClassCastException(badValueMsg(value)); 3938 return e.setValue(value); 3939 } 3940 3941 private String badValueMsg(Object value) { 3942 return "Attempt to insert " + value.getClass() + 3943 " value into map with value type " + valueType; 3944 } 3945 3946 public boolean equals(Object o) { 3947 if (o == this) 3948 return true; 3949 if (!(o instanceof Map.Entry)) 3950 return false; 3951 return e.equals(new AbstractMap.SimpleImmutableEntry 3952 <>((Map.Entry<?,?>)o)); 3953 } 3954 } 3955 } 3956 } 3957 3958 /** 3959 * Returns a dynamically typesafe view of the specified sorted map. 3960 * Any attempt to insert a mapping whose key or value have the wrong 3961 * type will result in an immediate {@link ClassCastException}. 3962 * Similarly, any attempt to modify the value currently associated with 3963 * a key will result in an immediate {@link ClassCastException}, 3964 * whether the modification is attempted directly through the map 3965 * itself, or through a {@link Map.Entry} instance obtained from the 3966 * map's {@link Map#entrySet() entry set} view. 3967 * 3968 * <p>Assuming a map contains no incorrectly typed keys or values 3969 * prior to the time a dynamically typesafe view is generated, and 3970 * that all subsequent access to the map takes place through the view 3971 * (or one of its collection views), it is <i>guaranteed</i> that the 3972 * map cannot contain an incorrectly typed key or value. 3973 * 3974 * <p>A discussion of the use of dynamically typesafe views may be 3975 * found in the documentation for the {@link #checkedCollection 3976 * checkedCollection} method. 3977 * 3978 * <p>The returned map will be serializable if the specified map is 3979 * serializable. 3980 * 3981 * <p>Since {@code null} is considered to be a value of any reference 3982 * type, the returned map permits insertion of null keys or values 3983 * whenever the backing map does. 3984 * 3985 * @param <K> the class of the map keys 3986 * @param <V> the class of the map values 3987 * @param m the map for which a dynamically typesafe view is to be 3988 * returned 3989 * @param keyType the type of key that {@code m} is permitted to hold 3990 * @param valueType the type of value that {@code m} is permitted to hold 3991 * @return a dynamically typesafe view of the specified map 3992 * @since 1.5 3993 */ 3994 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m, 3995 Class<K> keyType, 3996 Class<V> valueType) { 3997 return new CheckedSortedMap<>(m, keyType, valueType); 3998 } 3999 4000 /** 4001 * @serial include 4002 */ 4003 static class CheckedSortedMap<K,V> extends CheckedMap<K,V> 4004 implements SortedMap<K,V>, Serializable 4005 { 4006 private static final long serialVersionUID = 1599671320688067438L; 4007 4008 private final SortedMap<K, V> sm; 4009 4010 CheckedSortedMap(SortedMap<K, V> m, 4011 Class<K> keyType, Class<V> valueType) { 4012 super(m, keyType, valueType); 4013 sm = m; 4014 } 4015 4016 public Comparator<? super K> comparator() { return sm.comparator(); } 4017 public K firstKey() { return sm.firstKey(); } 4018 public K lastKey() { return sm.lastKey(); } 4019 4020 public SortedMap<K,V> subMap(K fromKey, K toKey) { 4021 return checkedSortedMap(sm.subMap(fromKey, toKey), 4022 keyType, valueType); 4023 } 4024 public SortedMap<K,V> headMap(K toKey) { 4025 return checkedSortedMap(sm.headMap(toKey), keyType, valueType); 4026 } 4027 public SortedMap<K,V> tailMap(K fromKey) { 4028 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType); 4029 } 4030 } 4031 4032 /** 4033 * Returns a dynamically typesafe view of the specified navigable map. 4034 * Any attempt to insert a mapping whose key or value have the wrong 4035 * type will result in an immediate {@link ClassCastException}. 4036 * Similarly, any attempt to modify the value currently associated with 4037 * a key will result in an immediate {@link ClassCastException}, 4038 * whether the modification is attempted directly through the map 4039 * itself, or through a {@link Map.Entry} instance obtained from the 4040 * map's {@link Map#entrySet() entry set} view. 4041 * 4042 * <p>Assuming a map contains no incorrectly typed keys or values 4043 * prior to the time a dynamically typesafe view is generated, and 4044 * that all subsequent access to the map takes place through the view 4045 * (or one of its collection views), it is <em>guaranteed</em> that the 4046 * map cannot contain an incorrectly typed key or value. 4047 * 4048 * <p>A discussion of the use of dynamically typesafe views may be 4049 * found in the documentation for the {@link #checkedCollection 4050 * checkedCollection} method. 4051 * 4052 * <p>The returned map will be serializable if the specified map is 4053 * serializable. 4054 * 4055 * <p>Since {@code null} is considered to be a value of any reference 4056 * type, the returned map permits insertion of null keys or values 4057 * whenever the backing map does. 4058 * 4059 * @param <K> type of map keys 4060 * @param <V> type of map values 4061 * @param m the map for which a dynamically typesafe view is to be 4062 * returned 4063 * @param keyType the type of key that {@code m} is permitted to hold 4064 * @param valueType the type of value that {@code m} is permitted to hold 4065 * @return a dynamically typesafe view of the specified map 4066 * @since 1.8 4067 */ 4068 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m, 4069 Class<K> keyType, 4070 Class<V> valueType) { 4071 return new CheckedNavigableMap<>(m, keyType, valueType); 4072 } 4073 4074 /** 4075 * @serial include 4076 */ 4077 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V> 4078 implements NavigableMap<K,V>, Serializable 4079 { 4080 private static final long serialVersionUID = -4852462692372534096L; 4081 4082 private final NavigableMap<K, V> nm; 4083 4084 CheckedNavigableMap(NavigableMap<K, V> m, 4085 Class<K> keyType, Class<V> valueType) { 4086 super(m, keyType, valueType); 4087 nm = m; 4088 } 4089 4090 public Comparator<? super K> comparator() { return nm.comparator(); } 4091 public K firstKey() { return nm.firstKey(); } 4092 public K lastKey() { return nm.lastKey(); } 4093 4094 public Entry<K, V> lowerEntry(K key) { 4095 Entry<K,V> lower = nm.lowerEntry(key); 4096 return (null != lower) 4097 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(lower, valueType) 4098 : null; 4099 } 4100 4101 public K lowerKey(K key) { return nm.lowerKey(key); } 4102 4103 public Entry<K, V> floorEntry(K key) { 4104 Entry<K,V> floor = nm.floorEntry(key); 4105 return (null != floor) 4106 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(floor, valueType) 4107 : null; 4108 } 4109 4110 public K floorKey(K key) { return nm.floorKey(key); } 4111 4112 public Entry<K, V> ceilingEntry(K key) { 4113 Entry<K,V> ceiling = nm.ceilingEntry(key); 4114 return (null != ceiling) 4115 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(ceiling, valueType) 4116 : null; 4117 } 4118 4119 public K ceilingKey(K key) { return nm.ceilingKey(key); } 4120 4121 public Entry<K, V> higherEntry(K key) { 4122 Entry<K,V> higher = nm.higherEntry(key); 4123 return (null != higher) 4124 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(higher, valueType) 4125 : null; 4126 } 4127 4128 public K higherKey(K key) { return nm.higherKey(key); } 4129 4130 public Entry<K, V> firstEntry() { 4131 Entry<K,V> first = nm.firstEntry(); 4132 return (null != first) 4133 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(first, valueType) 4134 : null; 4135 } 4136 4137 public Entry<K, V> lastEntry() { 4138 Entry<K,V> last = nm.lastEntry(); 4139 return (null != last) 4140 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(last, valueType) 4141 : null; 4142 } 4143 4144 public Entry<K, V> pollFirstEntry() { 4145 Entry<K,V> entry = nm.pollFirstEntry(); 4146 return (null == entry) 4147 ? null 4148 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4149 } 4150 4151 public Entry<K, V> pollLastEntry() { 4152 Entry<K,V> entry = nm.pollLastEntry(); 4153 return (null == entry) 4154 ? null 4155 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4156 } 4157 4158 public NavigableMap<K, V> descendingMap() { 4159 return checkedNavigableMap(nm.descendingMap(), keyType, valueType); 4160 } 4161 4162 public NavigableSet<K> keySet() { 4163 return navigableKeySet(); 4164 } 4165 4166 public NavigableSet<K> navigableKeySet() { 4167 return checkedNavigableSet(nm.navigableKeySet(), keyType); 4168 } 4169 4170 public NavigableSet<K> descendingKeySet() { 4171 return checkedNavigableSet(nm.descendingKeySet(), keyType); 4172 } 4173 4174 @Override 4175 public NavigableMap<K,V> subMap(K fromKey, K toKey) { 4176 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false), 4177 keyType, valueType); 4178 } 4179 4180 @Override 4181 public NavigableMap<K,V> headMap(K toKey) { 4182 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType); 4183 } 4184 4185 @Override 4186 public NavigableMap<K,V> tailMap(K fromKey) { 4187 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType); 4188 } 4189 4190 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 4191 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType); 4192 } 4193 4194 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) { 4195 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType); 4196 } 4197 4198 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) { 4199 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType); 4200 } 4201 } 4202 4203 // Empty collections 4204 4205 /** 4206 * Returns an iterator that has no elements. More precisely, 4207 * 4208 * <ul> 4209 * <li>{@link Iterator#hasNext hasNext} always returns {@code 4210 * false}.</li> 4211 * <li>{@link Iterator#next next} always throws {@link 4212 * NoSuchElementException}.</li> 4213 * <li>{@link Iterator#remove remove} always throws {@link 4214 * IllegalStateException}.</li> 4215 * </ul> 4216 * 4217 * <p>Implementations of this method are permitted, but not 4218 * required, to return the same object from multiple invocations. 4219 * 4220 * @param <T> type of elements, if there were any, in the iterator 4221 * @return an empty iterator 4222 * @since 1.7 4223 */ 4224 @SuppressWarnings("unchecked") 4225 public static <T> Iterator<T> emptyIterator() { 4226 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR; 4227 } 4228 4229 private static class EmptyIterator<E> implements Iterator<E> { 4230 static final EmptyIterator<Object> EMPTY_ITERATOR 4231 = new EmptyIterator<>(); 4232 4233 public boolean hasNext() { return false; } 4234 public E next() { throw new NoSuchElementException(); } 4235 public void remove() { throw new IllegalStateException(); } 4236 @Override 4237 public void forEachRemaining(Consumer<? super E> action) { 4238 Objects.requireNonNull(action); 4239 } 4240 } 4241 4242 /** 4243 * Returns a list iterator that has no elements. More precisely, 4244 * 4245 * <ul> 4246 * <li>{@link Iterator#hasNext hasNext} and {@link 4247 * ListIterator#hasPrevious hasPrevious} always return {@code 4248 * false}.</li> 4249 * <li>{@link Iterator#next next} and {@link ListIterator#previous 4250 * previous} always throw {@link NoSuchElementException}.</li> 4251 * <li>{@link Iterator#remove remove} and {@link ListIterator#set 4252 * set} always throw {@link IllegalStateException}.</li> 4253 * <li>{@link ListIterator#add add} always throws {@link 4254 * UnsupportedOperationException}.</li> 4255 * <li>{@link ListIterator#nextIndex nextIndex} always returns 4256 * {@code 0}.</li> 4257 * <li>{@link ListIterator#previousIndex previousIndex} always 4258 * returns {@code -1}.</li> 4259 * </ul> 4260 * 4261 * <p>Implementations of this method are permitted, but not 4262 * required, to return the same object from multiple invocations. 4263 * 4264 * @param <T> type of elements, if there were any, in the iterator 4265 * @return an empty list iterator 4266 * @since 1.7 4267 */ 4268 @SuppressWarnings("unchecked") 4269 public static <T> ListIterator<T> emptyListIterator() { 4270 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR; 4271 } 4272 4273 private static class EmptyListIterator<E> 4274 extends EmptyIterator<E> 4275 implements ListIterator<E> 4276 { 4277 static final EmptyListIterator<Object> EMPTY_ITERATOR 4278 = new EmptyListIterator<>(); 4279 4280 public boolean hasPrevious() { return false; } 4281 public E previous() { throw new NoSuchElementException(); } 4282 public int nextIndex() { return 0; } 4283 public int previousIndex() { return -1; } 4284 public void set(E e) { throw new IllegalStateException(); } 4285 public void add(E e) { throw new UnsupportedOperationException(); } 4286 } 4287 4288 /** 4289 * Returns an enumeration that has no elements. More precisely, 4290 * 4291 * <ul> 4292 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always 4293 * returns {@code false}.</li> 4294 * <li> {@link Enumeration#nextElement nextElement} always throws 4295 * {@link NoSuchElementException}.</li> 4296 * </ul> 4297 * 4298 * <p>Implementations of this method are permitted, but not 4299 * required, to return the same object from multiple invocations. 4300 * 4301 * @param <T> the class of the objects in the enumeration 4302 * @return an empty enumeration 4303 * @since 1.7 4304 */ 4305 @SuppressWarnings("unchecked") 4306 public static <T> Enumeration<T> emptyEnumeration() { 4307 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION; 4308 } 4309 4310 private static class EmptyEnumeration<E> implements Enumeration<E> { 4311 static final EmptyEnumeration<Object> EMPTY_ENUMERATION 4312 = new EmptyEnumeration<>(); 4313 4314 public boolean hasMoreElements() { return false; } 4315 public E nextElement() { throw new NoSuchElementException(); } 4316 } 4317 4318 /** 4319 * The empty set (immutable). This set is serializable. 4320 * 4321 * @see #emptySet() 4322 */ 4323 @SuppressWarnings("rawtypes") 4324 public static final Set EMPTY_SET = new EmptySet<>(); 4325 4326 /** 4327 * Returns an empty set (immutable). This set is serializable. 4328 * Unlike the like-named field, this method is parameterized. 4329 * 4330 * <p>This example illustrates the type-safe way to obtain an empty set: 4331 * <pre> 4332 * Set<String> s = Collections.emptySet(); 4333 * </pre> 4334 * @implNote Implementations of this method need not create a separate 4335 * {@code Set} object for each call. Using this method is likely to have 4336 * comparable cost to using the like-named field. (Unlike this method, the 4337 * field does not provide type safety.) 4338 * 4339 * @param <T> the class of the objects in the set 4340 * @return the empty set 4341 * 4342 * @see #EMPTY_SET 4343 * @since 1.5 4344 */ 4345 @SuppressWarnings("unchecked") 4346 public static final <T> Set<T> emptySet() { 4347 return (Set<T>) EMPTY_SET; 4348 } 4349 4350 /** 4351 * @serial include 4352 */ 4353 private static class EmptySet<E> 4354 extends AbstractSet<E> 4355 implements Serializable 4356 { 4357 private static final long serialVersionUID = 1582296315990362920L; 4358 4359 public Iterator<E> iterator() { return emptyIterator(); } 4360 4361 public int size() {return 0;} 4362 public boolean isEmpty() {return true;} 4363 4364 public boolean contains(Object obj) {return false;} 4365 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4366 4367 public Object[] toArray() { return new Object[0]; } 4368 4369 public <T> T[] toArray(T[] a) { 4370 if (a.length > 0) 4371 a[0] = null; 4372 return a; 4373 } 4374 4375 // Override default methods in Collection 4376 @Override 4377 public void forEach(Consumer<? super E> action) { 4378 Objects.requireNonNull(action); 4379 } 4380 @Override 4381 public boolean removeIf(Predicate<? super E> filter) { 4382 Objects.requireNonNull(filter); 4383 return false; 4384 } 4385 @Override 4386 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4387 4388 // Preserves singleton property 4389 private Object readResolve() { 4390 return EMPTY_SET; 4391 } 4392 } 4393 4394 /** 4395 * Returns an empty sorted set (immutable). This set is serializable. 4396 * 4397 * <p>This example illustrates the type-safe way to obtain an empty 4398 * sorted set: 4399 * <pre> {@code 4400 * SortedSet<String> s = Collections.emptySortedSet(); 4401 * }</pre> 4402 * 4403 * @implNote Implementations of this method need not create a separate 4404 * {@code SortedSet} object for each call. 4405 * 4406 * @param <E> type of elements, if there were any, in the set 4407 * @return the empty sorted set 4408 * @since 1.8 4409 */ 4410 @SuppressWarnings("unchecked") 4411 public static <E> SortedSet<E> emptySortedSet() { 4412 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4413 } 4414 4415 /** 4416 * Returns an empty navigable set (immutable). This set is serializable. 4417 * 4418 * <p>This example illustrates the type-safe way to obtain an empty 4419 * navigable set: 4420 * <pre> {@code 4421 * NavigableSet<String> s = Collections.emptyNavigableSet(); 4422 * }</pre> 4423 * 4424 * @implNote Implementations of this method need not 4425 * create a separate {@code NavigableSet} object for each call. 4426 * 4427 * @param <E> type of elements, if there were any, in the set 4428 * @return the empty navigable set 4429 * @since 1.8 4430 */ 4431 @SuppressWarnings("unchecked") 4432 public static <E> NavigableSet<E> emptyNavigableSet() { 4433 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4434 } 4435 4436 /** 4437 * The empty list (immutable). This list is serializable. 4438 * 4439 * @see #emptyList() 4440 */ 4441 @SuppressWarnings("rawtypes") 4442 public static final List EMPTY_LIST = new EmptyList<>(); 4443 4444 /** 4445 * Returns an empty list (immutable). This list is serializable. 4446 * 4447 * <p>This example illustrates the type-safe way to obtain an empty list: 4448 * <pre> 4449 * List<String> s = Collections.emptyList(); 4450 * </pre> 4451 * 4452 * @implNote 4453 * Implementations of this method need not create a separate <tt>List</tt> 4454 * object for each call. Using this method is likely to have comparable 4455 * cost to using the like-named field. (Unlike this method, the field does 4456 * not provide type safety.) 4457 * 4458 * @param <T> type of elements, if there were any, in the list 4459 * @return an empty immutable list 4460 * 4461 * @see #EMPTY_LIST 4462 * @since 1.5 4463 */ 4464 @SuppressWarnings("unchecked") 4465 public static final <T> List<T> emptyList() { 4466 return (List<T>) EMPTY_LIST; 4467 } 4468 4469 /** 4470 * @serial include 4471 */ 4472 private static class EmptyList<E> 4473 extends AbstractList<E> 4474 implements RandomAccess, Serializable { 4475 private static final long serialVersionUID = 8842843931221139166L; 4476 4477 public Iterator<E> iterator() { 4478 return emptyIterator(); 4479 } 4480 public ListIterator<E> listIterator() { 4481 return emptyListIterator(); 4482 } 4483 4484 public int size() {return 0;} 4485 public boolean isEmpty() {return true;} 4486 4487 public boolean contains(Object obj) {return false;} 4488 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4489 4490 public Object[] toArray() { return new Object[0]; } 4491 4492 public <T> T[] toArray(T[] a) { 4493 if (a.length > 0) 4494 a[0] = null; 4495 return a; 4496 } 4497 4498 public E get(int index) { 4499 throw new IndexOutOfBoundsException("Index: "+index); 4500 } 4501 4502 public boolean equals(Object o) { 4503 return (o instanceof List) && ((List<?>)o).isEmpty(); 4504 } 4505 4506 public int hashCode() { return 1; } 4507 4508 @Override 4509 public boolean removeIf(Predicate<? super E> filter) { 4510 Objects.requireNonNull(filter); 4511 return false; 4512 } 4513 @Override 4514 public void replaceAll(UnaryOperator<E> operator) { 4515 Objects.requireNonNull(operator); 4516 } 4517 @Override 4518 public void sort(Comparator<? super E> c) { 4519 } 4520 4521 // Override default methods in Collection 4522 @Override 4523 public void forEach(Consumer<? super E> action) { 4524 Objects.requireNonNull(action); 4525 } 4526 4527 @Override 4528 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4529 4530 // Preserves singleton property 4531 private Object readResolve() { 4532 return EMPTY_LIST; 4533 } 4534 } 4535 4536 /** 4537 * The empty map (immutable). This map is serializable. 4538 * 4539 * @see #emptyMap() 4540 * @since 1.3 4541 */ 4542 @SuppressWarnings("rawtypes") 4543 public static final Map EMPTY_MAP = new EmptyMap<>(); 4544 4545 /** 4546 * Returns an empty map (immutable). This map is serializable. 4547 * 4548 * <p>This example illustrates the type-safe way to obtain an empty map: 4549 * <pre> 4550 * Map<String, Date> s = Collections.emptyMap(); 4551 * </pre> 4552 * @implNote Implementations of this method need not create a separate 4553 * {@code Map} object for each call. Using this method is likely to have 4554 * comparable cost to using the like-named field. (Unlike this method, the 4555 * field does not provide type safety.) 4556 * 4557 * @param <K> the class of the map keys 4558 * @param <V> the class of the map values 4559 * @return an empty map 4560 * @see #EMPTY_MAP 4561 * @since 1.5 4562 */ 4563 @SuppressWarnings("unchecked") 4564 public static final <K,V> Map<K,V> emptyMap() { 4565 return (Map<K,V>) EMPTY_MAP; 4566 } 4567 4568 /** 4569 * Returns an empty sorted map (immutable). This map is serializable. 4570 * 4571 * <p>This example illustrates the type-safe way to obtain an empty map: 4572 * <pre> {@code 4573 * SortedMap<String, Date> s = Collections.emptySortedMap(); 4574 * }</pre> 4575 * 4576 * @implNote Implementations of this method need not create a separate 4577 * {@code SortedMap} object for each call. 4578 * 4579 * @param <K> the class of the map keys 4580 * @param <V> the class of the map values 4581 * @return an empty sorted map 4582 * @since 1.8 4583 */ 4584 @SuppressWarnings("unchecked") 4585 public static final <K,V> SortedMap<K,V> emptySortedMap() { 4586 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4587 } 4588 4589 /** 4590 * Returns an empty navigable map (immutable). This map is serializable. 4591 * 4592 * <p>This example illustrates the type-safe way to obtain an empty map: 4593 * <pre> {@code 4594 * NavigableMap<String, Date> s = Collections.emptyNavigableMap(); 4595 * }</pre> 4596 * 4597 * @implNote Implementations of this method need not create a separate 4598 * {@code NavigableMap} object for each call. 4599 * 4600 * @param <K> the class of the map keys 4601 * @param <V> the class of the map values 4602 * @return an empty navigable map 4603 * @since 1.8 4604 */ 4605 @SuppressWarnings("unchecked") 4606 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() { 4607 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4608 } 4609 4610 /** 4611 * @serial include 4612 */ 4613 private static class EmptyMap<K,V> 4614 extends AbstractMap<K,V> 4615 implements Serializable 4616 { 4617 private static final long serialVersionUID = 6428348081105594320L; 4618 4619 public int size() {return 0;} 4620 public boolean isEmpty() {return true;} 4621 public boolean containsKey(Object key) {return false;} 4622 public boolean containsValue(Object value) {return false;} 4623 public V get(Object key) {return null;} 4624 public Set<K> keySet() {return emptySet();} 4625 public Collection<V> values() {return emptySet();} 4626 public Set<Map.Entry<K,V>> entrySet() {return emptySet();} 4627 4628 public boolean equals(Object o) { 4629 return (o instanceof Map) && ((Map<?,?>)o).isEmpty(); 4630 } 4631 4632 public int hashCode() {return 0;} 4633 4634 // Override default methods in Map 4635 @Override 4636 @SuppressWarnings("unchecked") 4637 public V getOrDefault(Object k, V defaultValue) { 4638 return defaultValue; 4639 } 4640 4641 @Override 4642 public void forEach(BiConsumer<? super K, ? super V> action) { 4643 Objects.requireNonNull(action); 4644 } 4645 4646 @Override 4647 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4648 Objects.requireNonNull(function); 4649 } 4650 4651 @Override 4652 public V putIfAbsent(K key, V value) { 4653 throw new UnsupportedOperationException(); 4654 } 4655 4656 @Override 4657 public boolean remove(Object key, Object value) { 4658 throw new UnsupportedOperationException(); 4659 } 4660 4661 @Override 4662 public boolean replace(K key, V oldValue, V newValue) { 4663 throw new UnsupportedOperationException(); 4664 } 4665 4666 @Override 4667 public V replace(K key, V value) { 4668 throw new UnsupportedOperationException(); 4669 } 4670 4671 @Override 4672 public V computeIfAbsent(K key, 4673 Function<? super K, ? extends V> mappingFunction) { 4674 throw new UnsupportedOperationException(); 4675 } 4676 4677 @Override 4678 public V computeIfPresent(K key, 4679 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4680 throw new UnsupportedOperationException(); 4681 } 4682 4683 @Override 4684 public V compute(K key, 4685 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4686 throw new UnsupportedOperationException(); 4687 } 4688 4689 @Override 4690 public V merge(K key, V value, 4691 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 4692 throw new UnsupportedOperationException(); 4693 } 4694 4695 // Preserves singleton property 4696 private Object readResolve() { 4697 return EMPTY_MAP; 4698 } 4699 } 4700 4701 // Singleton collections 4702 4703 /** 4704 * Returns an immutable set containing only the specified object. 4705 * The returned set is serializable. 4706 * 4707 * @param <E> the class of the objects in the set 4708 * @param o the sole object to be stored in the returned set. 4709 * @return an immutable set containing only the specified object. 4710 */ 4711 public static <E> Set<E> singleton(E o) { 4712 return new SingletonSet<>(o); 4713 } 4714 4715 static <E> Iterator<E> singletonIterator(final E e) { 4716 return new Iterator<E>() { 4717 private boolean hasNext = true; 4718 public boolean hasNext() { 4719 return hasNext; 4720 } 4721 public E next() { 4722 if (hasNext) { 4723 hasNext = false; 4724 return e; 4725 } 4726 throw new NoSuchElementException(); 4727 } 4728 public void remove() { 4729 throw new UnsupportedOperationException(); 4730 } 4731 @Override 4732 public void forEachRemaining(Consumer<? super E> action) { 4733 Objects.requireNonNull(action); 4734 if (hasNext) { 4735 action.accept(e); 4736 hasNext = false; 4737 } 4738 } 4739 }; 4740 } 4741 4742 /** 4743 * Creates a {@code Spliterator} with only the specified element 4744 * 4745 * @param <T> Type of elements 4746 * @return A singleton {@code Spliterator} 4747 */ 4748 static <T> Spliterator<T> singletonSpliterator(final T element) { 4749 return new Spliterator<T>() { 4750 long est = 1; 4751 4752 @Override 4753 public Spliterator<T> trySplit() { 4754 return null; 4755 } 4756 4757 @Override 4758 public boolean tryAdvance(Consumer<? super T> consumer) { 4759 Objects.requireNonNull(consumer); 4760 if (est > 0) { 4761 est--; 4762 consumer.accept(element); 4763 return true; 4764 } 4765 return false; 4766 } 4767 4768 @Override 4769 public void forEachRemaining(Consumer<? super T> consumer) { 4770 tryAdvance(consumer); 4771 } 4772 4773 @Override 4774 public long estimateSize() { 4775 return est; 4776 } 4777 4778 @Override 4779 public int characteristics() { 4780 int value = (element != null) ? Spliterator.NONNULL : 0; 4781 4782 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE | 4783 Spliterator.DISTINCT | Spliterator.ORDERED; 4784 } 4785 }; 4786 } 4787 4788 /** 4789 * @serial include 4790 */ 4791 private static class SingletonSet<E> 4792 extends AbstractSet<E> 4793 implements Serializable 4794 { 4795 private static final long serialVersionUID = 3193687207550431679L; 4796 4797 private final E element; 4798 4799 SingletonSet(E e) {element = e;} 4800 4801 public Iterator<E> iterator() { 4802 return singletonIterator(element); 4803 } 4804 4805 public int size() {return 1;} 4806 4807 public boolean contains(Object o) {return eq(o, element);} 4808 4809 // Override default methods for Collection 4810 @Override 4811 public void forEach(Consumer<? super E> action) { 4812 action.accept(element); 4813 } 4814 @Override 4815 public Spliterator<E> spliterator() { 4816 return singletonSpliterator(element); 4817 } 4818 @Override 4819 public boolean removeIf(Predicate<? super E> filter) { 4820 throw new UnsupportedOperationException(); 4821 } 4822 } 4823 4824 /** 4825 * Returns an immutable list containing only the specified object. 4826 * The returned list is serializable. 4827 * 4828 * @param <E> the class of the objects in the list 4829 * @param o the sole object to be stored in the returned list. 4830 * @return an immutable list containing only the specified object. 4831 * @since 1.3 4832 */ 4833 public static <E> List<E> singletonList(E o) { 4834 return new SingletonList<>(o); 4835 } 4836 4837 /** 4838 * @serial include 4839 */ 4840 private static class SingletonList<E> 4841 extends AbstractList<E> 4842 implements RandomAccess, Serializable { 4843 4844 private static final long serialVersionUID = 3093736618740652951L; 4845 4846 private final E element; 4847 4848 SingletonList(E obj) {element = obj;} 4849 4850 public Iterator<E> iterator() { 4851 return singletonIterator(element); 4852 } 4853 4854 public int size() {return 1;} 4855 4856 public boolean contains(Object obj) {return eq(obj, element);} 4857 4858 public E get(int index) { 4859 if (index != 0) 4860 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1"); 4861 return element; 4862 } 4863 4864 // Override default methods for Collection 4865 @Override 4866 public void forEach(Consumer<? super E> action) { 4867 action.accept(element); 4868 } 4869 @Override 4870 public boolean removeIf(Predicate<? super E> filter) { 4871 throw new UnsupportedOperationException(); 4872 } 4873 @Override 4874 public void replaceAll(UnaryOperator<E> operator) { 4875 throw new UnsupportedOperationException(); 4876 } 4877 @Override 4878 public void sort(Comparator<? super E> c) { 4879 } 4880 @Override 4881 public Spliterator<E> spliterator() { 4882 return singletonSpliterator(element); 4883 } 4884 } 4885 4886 /** 4887 * Returns an immutable map, mapping only the specified key to the 4888 * specified value. The returned map is serializable. 4889 * 4890 * @param <K> the class of the map keys 4891 * @param <V> the class of the map values 4892 * @param key the sole key to be stored in the returned map. 4893 * @param value the value to which the returned map maps <tt>key</tt>. 4894 * @return an immutable map containing only the specified key-value 4895 * mapping. 4896 * @since 1.3 4897 */ 4898 public static <K,V> Map<K,V> singletonMap(K key, V value) { 4899 return new SingletonMap<>(key, value); 4900 } 4901 4902 /** 4903 * @serial include 4904 */ 4905 private static class SingletonMap<K,V> 4906 extends AbstractMap<K,V> 4907 implements Serializable { 4908 private static final long serialVersionUID = -6979724477215052911L; 4909 4910 private final K k; 4911 private final V v; 4912 4913 SingletonMap(K key, V value) { 4914 k = key; 4915 v = value; 4916 } 4917 4918 public int size() {return 1;} 4919 public boolean isEmpty() {return false;} 4920 public boolean containsKey(Object key) {return eq(key, k);} 4921 public boolean containsValue(Object value) {return eq(value, v);} 4922 public V get(Object key) {return (eq(key, k) ? v : null);} 4923 4924 private transient Set<K> keySet; 4925 private transient Set<Map.Entry<K,V>> entrySet; 4926 private transient Collection<V> values; 4927 4928 public Set<K> keySet() { 4929 if (keySet==null) 4930 keySet = singleton(k); 4931 return keySet; 4932 } 4933 4934 public Set<Map.Entry<K,V>> entrySet() { 4935 if (entrySet==null) 4936 entrySet = Collections.<Map.Entry<K,V>>singleton( 4937 new SimpleImmutableEntry<>(k, v)); 4938 return entrySet; 4939 } 4940 4941 public Collection<V> values() { 4942 if (values==null) 4943 values = singleton(v); 4944 return values; 4945 } 4946 4947 // Override default methods in Map 4948 @Override 4949 public V getOrDefault(Object key, V defaultValue) { 4950 return eq(key, k) ? v : defaultValue; 4951 } 4952 4953 @Override 4954 public void forEach(BiConsumer<? super K, ? super V> action) { 4955 action.accept(k, v); 4956 } 4957 4958 @Override 4959 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4960 throw new UnsupportedOperationException(); 4961 } 4962 4963 @Override 4964 public V putIfAbsent(K key, V value) { 4965 throw new UnsupportedOperationException(); 4966 } 4967 4968 @Override 4969 public boolean remove(Object key, Object value) { 4970 throw new UnsupportedOperationException(); 4971 } 4972 4973 @Override 4974 public boolean replace(K key, V oldValue, V newValue) { 4975 throw new UnsupportedOperationException(); 4976 } 4977 4978 @Override 4979 public V replace(K key, V value) { 4980 throw new UnsupportedOperationException(); 4981 } 4982 4983 @Override 4984 public V computeIfAbsent(K key, 4985 Function<? super K, ? extends V> mappingFunction) { 4986 throw new UnsupportedOperationException(); 4987 } 4988 4989 @Override 4990 public V computeIfPresent(K key, 4991 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4992 throw new UnsupportedOperationException(); 4993 } 4994 4995 @Override 4996 public V compute(K key, 4997 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4998 throw new UnsupportedOperationException(); 4999 } 5000 5001 @Override 5002 public V merge(K key, V value, 5003 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 5004 throw new UnsupportedOperationException(); 5005 } 5006 } 5007 5008 // Miscellaneous 5009 5010 /** 5011 * Returns an immutable list consisting of <tt>n</tt> copies of the 5012 * specified object. The newly allocated data object is tiny (it contains 5013 * a single reference to the data object). This method is useful in 5014 * combination with the <tt>List.addAll</tt> method to grow lists. 5015 * The returned list is serializable. 5016 * 5017 * @param <T> the class of the object to copy and of the objects 5018 * in the returned list. 5019 * @param n the number of elements in the returned list. 5020 * @param o the element to appear repeatedly in the returned list. 5021 * @return an immutable list consisting of <tt>n</tt> copies of the 5022 * specified object. 5023 * @throws IllegalArgumentException if {@code n < 0} 5024 * @see List#addAll(Collection) 5025 * @see List#addAll(int, Collection) 5026 */ 5027 public static <T> List<T> nCopies(int n, T o) { 5028 if (n < 0) 5029 throw new IllegalArgumentException("List length = " + n); 5030 return new CopiesList<>(n, o); 5031 } 5032 5033 /** 5034 * @serial include 5035 */ 5036 private static class CopiesList<E> 5037 extends AbstractList<E> 5038 implements RandomAccess, Serializable 5039 { 5040 private static final long serialVersionUID = 2739099268398711800L; 5041 5042 final int n; 5043 final E element; 5044 5045 CopiesList(int n, E e) { 5046 assert n >= 0; 5047 this.n = n; 5048 element = e; 5049 } 5050 5051 public int size() { 5052 return n; 5053 } 5054 5055 public boolean contains(Object obj) { 5056 return n != 0 && eq(obj, element); 5057 } 5058 5059 public int indexOf(Object o) { 5060 return contains(o) ? 0 : -1; 5061 } 5062 5063 public int lastIndexOf(Object o) { 5064 return contains(o) ? n - 1 : -1; 5065 } 5066 5067 public E get(int index) { 5068 if (index < 0 || index >= n) 5069 throw new IndexOutOfBoundsException("Index: "+index+ 5070 ", Size: "+n); 5071 return element; 5072 } 5073 5074 public Object[] toArray() { 5075 final Object[] a = new Object[n]; 5076 if (element != null) 5077 Arrays.fill(a, 0, n, element); 5078 return a; 5079 } 5080 5081 @SuppressWarnings("unchecked") 5082 public <T> T[] toArray(T[] a) { 5083 final int n = this.n; 5084 if (a.length < n) { 5085 a = (T[])java.lang.reflect.Array 5086 .newInstance(a.getClass().getComponentType(), n); 5087 if (element != null) 5088 Arrays.fill(a, 0, n, element); 5089 } else { 5090 Arrays.fill(a, 0, n, element); 5091 if (a.length > n) 5092 a[n] = null; 5093 } 5094 return a; 5095 } 5096 5097 public List<E> subList(int fromIndex, int toIndex) { 5098 if (fromIndex < 0) 5099 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); 5100 if (toIndex > n) 5101 throw new IndexOutOfBoundsException("toIndex = " + toIndex); 5102 if (fromIndex > toIndex) 5103 throw new IllegalArgumentException("fromIndex(" + fromIndex + 5104 ") > toIndex(" + toIndex + ")"); 5105 return new CopiesList<>(toIndex - fromIndex, element); 5106 } 5107 5108 // Override default methods in Collection 5109 @Override 5110 public Stream<E> stream() { 5111 return IntStream.range(0, n).mapToObj(i -> element); 5112 } 5113 5114 @Override 5115 public Stream<E> parallelStream() { 5116 return IntStream.range(0, n).parallel().mapToObj(i -> element); 5117 } 5118 5119 @Override 5120 public Spliterator<E> spliterator() { 5121 return stream().spliterator(); 5122 } 5123 } 5124 5125 /** 5126 * Returns a comparator that imposes the reverse of the <em>natural 5127 * ordering</em> on a collection of objects that implement the 5128 * {@code Comparable} interface. (The natural ordering is the ordering 5129 * imposed by the objects' own {@code compareTo} method.) This enables a 5130 * simple idiom for sorting (or maintaining) collections (or arrays) of 5131 * objects that implement the {@code Comparable} interface in 5132 * reverse-natural-order. For example, suppose {@code a} is an array of 5133 * strings. Then: <pre> 5134 * Arrays.sort(a, Collections.reverseOrder()); 5135 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p> 5136 * 5137 * The returned comparator is serializable. 5138 * 5139 * @param <T> the class of the objects compared by the comparator 5140 * @return A comparator that imposes the reverse of the <i>natural 5141 * ordering</i> on a collection of objects that implement 5142 * the <tt>Comparable</tt> interface. 5143 * @see Comparable 5144 */ 5145 @SuppressWarnings("unchecked") 5146 public static <T> Comparator<T> reverseOrder() { 5147 return (Comparator<T>) ReverseComparator.REVERSE_ORDER; 5148 } 5149 5150 /** 5151 * @serial include 5152 */ 5153 private static class ReverseComparator 5154 implements Comparator<Comparable<Object>>, Serializable { 5155 5156 private static final long serialVersionUID = 7207038068494060240L; 5157 5158 static final ReverseComparator REVERSE_ORDER 5159 = new ReverseComparator(); 5160 5161 public int compare(Comparable<Object> c1, Comparable<Object> c2) { 5162 return c2.compareTo(c1); 5163 } 5164 5165 private Object readResolve() { return Collections.reverseOrder(); } 5166 5167 @Override 5168 public Comparator<Comparable<Object>> reversed() { 5169 return Comparator.naturalOrder(); 5170 } 5171 } 5172 5173 /** 5174 * Returns a comparator that imposes the reverse ordering of the specified 5175 * comparator. If the specified comparator is {@code null}, this method is 5176 * equivalent to {@link #reverseOrder()} (in other words, it returns a 5177 * comparator that imposes the reverse of the <em>natural ordering</em> on 5178 * a collection of objects that implement the Comparable interface). 5179 * 5180 * <p>The returned comparator is serializable (assuming the specified 5181 * comparator is also serializable or {@code null}). 5182 * 5183 * @param <T> the class of the objects compared by the comparator 5184 * @param cmp a comparator who's ordering is to be reversed by the returned 5185 * comparator or {@code null} 5186 * @return A comparator that imposes the reverse ordering of the 5187 * specified comparator. 5188 * @since 1.5 5189 */ 5190 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) { 5191 if (cmp == null) 5192 return reverseOrder(); 5193 5194 if (cmp instanceof ReverseComparator2) 5195 return ((ReverseComparator2<T>)cmp).cmp; 5196 5197 return new ReverseComparator2<>(cmp); 5198 } 5199 5200 /** 5201 * @serial include 5202 */ 5203 private static class ReverseComparator2<T> implements Comparator<T>, 5204 Serializable 5205 { 5206 private static final long serialVersionUID = 4374092139857L; 5207 5208 /** 5209 * The comparator specified in the static factory. This will never 5210 * be null, as the static factory returns a ReverseComparator 5211 * instance if its argument is null. 5212 * 5213 * @serial 5214 */ 5215 final Comparator<T> cmp; 5216 5217 ReverseComparator2(Comparator<T> cmp) { 5218 assert cmp != null; 5219 this.cmp = cmp; 5220 } 5221 5222 public int compare(T t1, T t2) { 5223 return cmp.compare(t2, t1); 5224 } 5225 5226 public boolean equals(Object o) { 5227 return (o == this) || 5228 (o instanceof ReverseComparator2 && 5229 cmp.equals(((ReverseComparator2)o).cmp)); 5230 } 5231 5232 public int hashCode() { 5233 return cmp.hashCode() ^ Integer.MIN_VALUE; 5234 } 5235 5236 @Override 5237 public Comparator<T> reversed() { 5238 return cmp; 5239 } 5240 } 5241 5242 /** 5243 * Returns an enumeration over the specified collection. This provides 5244 * interoperability with legacy APIs that require an enumeration 5245 * as input. 5246 * 5247 * @param <T> the class of the objects in the collection 5248 * @param c the collection for which an enumeration is to be returned. 5249 * @return an enumeration over the specified collection. 5250 * @see Enumeration 5251 */ 5252 public static <T> Enumeration<T> enumeration(final Collection<T> c) { 5253 return new Enumeration<T>() { 5254 private final Iterator<T> i = c.iterator(); 5255 5256 public boolean hasMoreElements() { 5257 return i.hasNext(); 5258 } 5259 5260 public T nextElement() { 5261 return i.next(); 5262 } 5263 }; 5264 } 5265 5266 /** 5267 * Returns an array list containing the elements returned by the 5268 * specified enumeration in the order they are returned by the 5269 * enumeration. This method provides interoperability between 5270 * legacy APIs that return enumerations and new APIs that require 5271 * collections. 5272 * 5273 * @param <T> the class of the objects returned by the enumeration 5274 * @param e enumeration providing elements for the returned 5275 * array list 5276 * @return an array list containing the elements returned 5277 * by the specified enumeration. 5278 * @since 1.4 5279 * @see Enumeration 5280 * @see ArrayList 5281 */ 5282 public static <T> ArrayList<T> list(Enumeration<T> e) { 5283 ArrayList<T> l = new ArrayList<>(); 5284 while (e.hasMoreElements()) 5285 l.add(e.nextElement()); 5286 return l; 5287 } 5288 5289 /** 5290 * Returns true if the specified arguments are equal, or both null. 5291 * 5292 * NB: Do not replace with Object.equals until JDK-8015417 is resolved. 5293 */ 5294 static boolean eq(Object o1, Object o2) { 5295 return o1==null ? o2==null : o1.equals(o2); 5296 } 5297 5298 /** 5299 * Returns the number of elements in the specified collection equal to the 5300 * specified object. More formally, returns the number of elements 5301 * <tt>e</tt> in the collection such that 5302 * <tt>(o == null ? e == null : o.equals(e))</tt>. 5303 * 5304 * @param c the collection in which to determine the frequency 5305 * of <tt>o</tt> 5306 * @param o the object whose frequency is to be determined 5307 * @return the number of elements in {@code c} equal to {@code o} 5308 * @throws NullPointerException if <tt>c</tt> is null 5309 * @since 1.5 5310 */ 5311 public static int frequency(Collection<?> c, Object o) { 5312 int result = 0; 5313 if (o == null) { 5314 for (Object e : c) 5315 if (e == null) 5316 result++; 5317 } else { 5318 for (Object e : c) 5319 if (o.equals(e)) 5320 result++; 5321 } 5322 return result; 5323 } 5324 5325 /** 5326 * Returns {@code true} if the two specified collections have no 5327 * elements in common. 5328 * 5329 * <p>Care must be exercised if this method is used on collections that 5330 * do not comply with the general contract for {@code Collection}. 5331 * Implementations may elect to iterate over either collection and test 5332 * for containment in the other collection (or to perform any equivalent 5333 * computation). If either collection uses a nonstandard equality test 5334 * (as does a {@link SortedSet} whose ordering is not <em>compatible with 5335 * equals</em>, or the key set of an {@link IdentityHashMap}), both 5336 * collections must use the same nonstandard equality test, or the 5337 * result of this method is undefined. 5338 * 5339 * <p>Care must also be exercised when using collections that have 5340 * restrictions on the elements that they may contain. Collection 5341 * implementations are allowed to throw exceptions for any operation 5342 * involving elements they deem ineligible. For absolute safety the 5343 * specified collections should contain only elements which are 5344 * eligible elements for both collections. 5345 * 5346 * <p>Note that it is permissible to pass the same collection in both 5347 * parameters, in which case the method will return {@code true} if and 5348 * only if the collection is empty. 5349 * 5350 * @param c1 a collection 5351 * @param c2 a collection 5352 * @return {@code true} if the two specified collections have no 5353 * elements in common. 5354 * @throws NullPointerException if either collection is {@code null}. 5355 * @throws NullPointerException if one collection contains a {@code null} 5356 * element and {@code null} is not an eligible element for the other collection. 5357 * (<a href="Collection.html#optional-restrictions">optional</a>) 5358 * @throws ClassCastException if one collection contains an element that is 5359 * of a type which is ineligible for the other collection. 5360 * (<a href="Collection.html#optional-restrictions">optional</a>) 5361 * @since 1.5 5362 */ 5363 public static boolean disjoint(Collection<?> c1, Collection<?> c2) { 5364 // The collection to be used for contains(). Preference is given to 5365 // the collection who's contains() has lower O() complexity. 5366 Collection<?> contains = c2; 5367 // The collection to be iterated. If the collections' contains() impl 5368 // are of different O() complexity, the collection with slower 5369 // contains() will be used for iteration. For collections who's 5370 // contains() are of the same complexity then best performance is 5371 // achieved by iterating the smaller collection. 5372 Collection<?> iterate = c1; 5373 5374 // Performance optimization cases. The heuristics: 5375 // 1. Generally iterate over c1. 5376 // 2. If c1 is a Set then iterate over c2. 5377 // 3. If either collection is empty then result is always true. 5378 // 4. Iterate over the smaller Collection. 5379 if (c1 instanceof Set) { 5380 // Use c1 for contains as a Set's contains() is expected to perform 5381 // better than O(N/2) 5382 iterate = c2; 5383 contains = c1; 5384 } else if (!(c2 instanceof Set)) { 5385 // Both are mere Collections. Iterate over smaller collection. 5386 // Example: If c1 contains 3 elements and c2 contains 50 elements and 5387 // assuming contains() requires ceiling(N/2) comparisons then 5388 // checking for all c1 elements in c2 would require 75 comparisons 5389 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring 5390 // 100 comparisons (50 * ceiling(3/2)). 5391 int c1size = c1.size(); 5392 int c2size = c2.size(); 5393 if (c1size == 0 || c2size == 0) { 5394 // At least one collection is empty. Nothing will match. 5395 return true; 5396 } 5397 5398 if (c1size > c2size) { 5399 iterate = c2; 5400 contains = c1; 5401 } 5402 } 5403 5404 for (Object e : iterate) { 5405 if (contains.contains(e)) { 5406 // Found a common element. Collections are not disjoint. 5407 return false; 5408 } 5409 } 5410 5411 // No common elements were found. 5412 return true; 5413 } 5414 5415 /** 5416 * Adds all of the specified elements to the specified collection. 5417 * Elements to be added may be specified individually or as an array. 5418 * The behavior of this convenience method is identical to that of 5419 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely 5420 * to run significantly faster under most implementations. 5421 * 5422 * <p>When elements are specified individually, this method provides a 5423 * convenient way to add a few elements to an existing collection: 5424 * <pre> 5425 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon"); 5426 * </pre> 5427 * 5428 * @param <T> the class of the elements to add and of the collection 5429 * @param c the collection into which <tt>elements</tt> are to be inserted 5430 * @param elements the elements to insert into <tt>c</tt> 5431 * @return <tt>true</tt> if the collection changed as a result of the call 5432 * @throws UnsupportedOperationException if <tt>c</tt> does not support 5433 * the <tt>add</tt> operation 5434 * @throws NullPointerException if <tt>elements</tt> contains one or more 5435 * null values and <tt>c</tt> does not permit null elements, or 5436 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt> 5437 * @throws IllegalArgumentException if some property of a value in 5438 * <tt>elements</tt> prevents it from being added to <tt>c</tt> 5439 * @see Collection#addAll(Collection) 5440 * @since 1.5 5441 */ 5442 @SafeVarargs 5443 public static <T> boolean addAll(Collection<? super T> c, T... elements) { 5444 boolean result = false; 5445 for (T element : elements) 5446 result |= c.add(element); 5447 return result; 5448 } 5449 5450 /** 5451 * Returns a set backed by the specified map. The resulting set displays 5452 * the same ordering, concurrency, and performance characteristics as the 5453 * backing map. In essence, this factory method provides a {@link Set} 5454 * implementation corresponding to any {@link Map} implementation. There 5455 * is no need to use this method on a {@link Map} implementation that 5456 * already has a corresponding {@link Set} implementation (such as {@link 5457 * HashMap} or {@link TreeMap}). 5458 * 5459 * <p>Each method invocation on the set returned by this method results in 5460 * exactly one method invocation on the backing map or its <tt>keySet</tt> 5461 * view, with one exception. The <tt>addAll</tt> method is implemented 5462 * as a sequence of <tt>put</tt> invocations on the backing map. 5463 * 5464 * <p>The specified map must be empty at the time this method is invoked, 5465 * and should not be accessed directly after this method returns. These 5466 * conditions are ensured if the map is created empty, passed directly 5467 * to this method, and no reference to the map is retained, as illustrated 5468 * in the following code fragment: 5469 * <pre> 5470 * Set<Object> weakHashSet = Collections.newSetFromMap( 5471 * new WeakHashMap<Object, Boolean>()); 5472 * </pre> 5473 * 5474 * @param <E> the class of the map keys and of the objects in the 5475 * returned set 5476 * @param map the backing map 5477 * @return the set backed by the map 5478 * @throws IllegalArgumentException if <tt>map</tt> is not empty 5479 * @since 1.6 5480 */ 5481 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) { 5482 return new SetFromMap<>(map); 5483 } 5484 5485 /** 5486 * @serial include 5487 */ 5488 private static class SetFromMap<E> extends AbstractSet<E> 5489 implements Set<E>, Serializable 5490 { 5491 private final Map<E, Boolean> m; // The backing map 5492 private transient Set<E> s; // Its keySet 5493 5494 SetFromMap(Map<E, Boolean> map) { 5495 if (!map.isEmpty()) 5496 throw new IllegalArgumentException("Map is non-empty"); 5497 m = map; 5498 s = map.keySet(); 5499 } 5500 5501 public void clear() { m.clear(); } 5502 public int size() { return m.size(); } 5503 public boolean isEmpty() { return m.isEmpty(); } 5504 public boolean contains(Object o) { return m.containsKey(o); } 5505 public boolean remove(Object o) { return m.remove(o) != null; } 5506 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; } 5507 public Iterator<E> iterator() { return s.iterator(); } 5508 public Object[] toArray() { return s.toArray(); } 5509 public <T> T[] toArray(T[] a) { return s.toArray(a); } 5510 public String toString() { return s.toString(); } 5511 public int hashCode() { return s.hashCode(); } 5512 public boolean equals(Object o) { return o == this || s.equals(o); } 5513 public boolean containsAll(Collection<?> c) {return s.containsAll(c);} 5514 public boolean removeAll(Collection<?> c) {return s.removeAll(c);} 5515 public boolean retainAll(Collection<?> c) {return s.retainAll(c);} 5516 // addAll is the only inherited implementation 5517 5518 // Override default methods in Collection 5519 @Override 5520 public void forEach(Consumer<? super E> action) { 5521 s.forEach(action); 5522 } 5523 @Override 5524 public boolean removeIf(Predicate<? super E> filter) { 5525 return s.removeIf(filter); 5526 } 5527 5528 @Override 5529 public Spliterator<E> spliterator() {return s.spliterator();} 5530 @Override 5531 public Stream<E> stream() {return s.stream();} 5532 @Override 5533 public Stream<E> parallelStream() {return s.parallelStream();} 5534 5535 private static final long serialVersionUID = 2454657854757543876L; 5536 5537 private void readObject(java.io.ObjectInputStream stream) 5538 throws IOException, ClassNotFoundException 5539 { 5540 stream.defaultReadObject(); 5541 s = m.keySet(); 5542 } 5543 } 5544 5545 /** 5546 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo) 5547 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>, 5548 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This 5549 * view can be useful when you would like to use a method 5550 * requiring a <tt>Queue</tt> but you need Lifo ordering. 5551 * 5552 * <p>Each method invocation on the queue returned by this method 5553 * results in exactly one method invocation on the backing deque, with 5554 * one exception. The {@link Queue#addAll addAll} method is 5555 * implemented as a sequence of {@link Deque#addFirst addFirst} 5556 * invocations on the backing deque. 5557 * 5558 * @param <T> the class of the objects in the deque 5559 * @param deque the deque 5560 * @return the queue 5561 * @since 1.6 5562 */ 5563 public static <T> Queue<T> asLifoQueue(Deque<T> deque) { 5564 return new AsLIFOQueue<>(deque); 5565 } 5566 5567 /** 5568 * @serial include 5569 */ 5570 static class AsLIFOQueue<E> extends AbstractQueue<E> 5571 implements Queue<E>, Serializable { 5572 private static final long serialVersionUID = 1802017725587941708L; 5573 private final Deque<E> q; 5574 AsLIFOQueue(Deque<E> q) { this.q = q; } 5575 public boolean add(E e) { q.addFirst(e); return true; } 5576 public boolean offer(E e) { return q.offerFirst(e); } 5577 public E poll() { return q.pollFirst(); } 5578 public E remove() { return q.removeFirst(); } 5579 public E peek() { return q.peekFirst(); } 5580 public E element() { return q.getFirst(); } 5581 public void clear() { q.clear(); } 5582 public int size() { return q.size(); } 5583 public boolean isEmpty() { return q.isEmpty(); } 5584 public boolean contains(Object o) { return q.contains(o); } 5585 public boolean remove(Object o) { return q.remove(o); } 5586 public Iterator<E> iterator() { return q.iterator(); } 5587 public Object[] toArray() { return q.toArray(); } 5588 public <T> T[] toArray(T[] a) { return q.toArray(a); } 5589 public String toString() { return q.toString(); } 5590 public boolean containsAll(Collection<?> c) {return q.containsAll(c);} 5591 public boolean removeAll(Collection<?> c) {return q.removeAll(c);} 5592 public boolean retainAll(Collection<?> c) {return q.retainAll(c);} 5593 // We use inherited addAll; forwarding addAll would be wrong 5594 5595 // Override default methods in Collection 5596 @Override 5597 public void forEach(Consumer<? super E> action) {q.forEach(action);} 5598 @Override 5599 public boolean removeIf(Predicate<? super E> filter) { 5600 return q.removeIf(filter); 5601 } 5602 @Override 5603 public Spliterator<E> spliterator() {return q.spliterator();} 5604 @Override 5605 public Stream<E> stream() {return q.stream();} 5606 @Override 5607 public Stream<E> parallelStream() {return q.parallelStream();} 5608 } 5609} 5610