Collections.java revision 44d40c2a5aa1f60f1d137a6734f7fa21e445c5a0
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 44/** 45 * This class consists exclusively of static methods that operate on or return 46 * collections. It contains polymorphic algorithms that operate on 47 * collections, "wrappers", which return a new collection backed by a 48 * specified collection, and a few other odds and ends. 49 * 50 * <p>The methods of this class all throw a <tt>NullPointerException</tt> 51 * if the collections or class objects provided to them are null. 52 * 53 * <p>The documentation for the polymorphic algorithms contained in this class 54 * generally includes a brief description of the <i>implementation</i>. Such 55 * descriptions should be regarded as <i>implementation notes</i>, rather than 56 * parts of the <i>specification</i>. Implementors should feel free to 57 * substitute other algorithms, so long as the specification itself is adhered 58 * to. (For example, the algorithm used by <tt>sort</tt> does not have to be 59 * a mergesort, but it does have to be <i>stable</i>.) 60 * 61 * <p>The "destructive" algorithms contained in this class, that is, the 62 * algorithms that modify the collection on which they operate, are specified 63 * to throw <tt>UnsupportedOperationException</tt> if the collection does not 64 * support the appropriate mutation primitive(s), such as the <tt>set</tt> 65 * method. These algorithms may, but are not required to, throw this 66 * exception if an invocation would have no effect on the collection. For 67 * example, invoking the <tt>sort</tt> method on an unmodifiable list that is 68 * already sorted may or may not throw <tt>UnsupportedOperationException</tt>. 69 * 70 * <p>This class is a member of the 71 * <a href="{@docRoot}openjdk-redirect.html?v=8&path=/technotes/guides/collections/index.html"> 72 * Java Collections Framework</a>. 73 * 74 * @author Josh Bloch 75 * @author Neal Gafter 76 * @see Collection 77 * @see Set 78 * @see List 79 * @see Map 80 * @since 1.2 81 */ 82 83public class Collections { 84 // Suppresses default constructor, ensuring non-instantiability. 85 private Collections() { 86 } 87 88 // Algorithms 89 90 /* 91 * Tuning parameters for algorithms - Many of the List algorithms have 92 * two implementations, one of which is appropriate for RandomAccess 93 * lists, the other for "sequential." Often, the random access variant 94 * yields better performance on small sequential access lists. The 95 * tuning parameters below determine the cutoff point for what constitutes 96 * a "small" sequential access list for each algorithm. The values below 97 * were empirically determined to work well for LinkedList. Hopefully 98 * they should be reasonable for other sequential access List 99 * implementations. Those doing performance work on this code would 100 * do well to validate the values of these parameters from time to time. 101 * (The first word of each tuning parameter name is the algorithm to which 102 * it applies.) 103 */ 104 private static final int BINARYSEARCH_THRESHOLD = 5000; 105 private static final int REVERSE_THRESHOLD = 18; 106 private static final int SHUFFLE_THRESHOLD = 5; 107 private static final int FILL_THRESHOLD = 25; 108 private static final int ROTATE_THRESHOLD = 100; 109 private static final int COPY_THRESHOLD = 10; 110 private static final int REPLACEALL_THRESHOLD = 11; 111 private static final int INDEXOFSUBLIST_THRESHOLD = 35; 112 113 // Android-changed: Warn about Collections.sort() being built on top 114 // of List.sort() when it used to be the other way round in Nougat. 115 /** 116 * Sorts the specified list into ascending order, according to the 117 * {@linkplain Comparable natural ordering} of its elements. 118 * All elements in the list must implement the {@link Comparable} 119 * interface. Furthermore, all elements in the list must be 120 * <i>mutually comparable</i> (that is, {@code e1.compareTo(e2)} 121 * must not throw a {@code ClassCastException} for any elements 122 * {@code e1} and {@code e2} in the list). 123 * 124 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will 125 * not be reordered as a result of the sort. 126 * 127 * <p>The specified list must be modifiable, but need not be resizable. 128 * 129 * @implNote 130 * This implementation defers to the {@link List#sort(Comparator)} 131 * method using the specified list and a {@code null} comparator. 132 * Note that in Android 7 (Nougat), {@code Collections.sort()} used to 133 * be implemented on top of {@link List#toArray()}, 134 * {@link ListIterator#next()} and {@link ListIterator#set(Object)}. 135 * 136 * @param <T> the class of the objects in the list 137 * @param list the list to be sorted. 138 * @throws ClassCastException if the list contains elements that are not 139 * <i>mutually comparable</i> (for example, strings and integers). 140 * @throws UnsupportedOperationException if the specified list's 141 * list-iterator does not support the {@code set} operation. 142 * @throws IllegalArgumentException (optional) if the implementation 143 * detects that the natural ordering of the list elements is 144 * found to violate the {@link Comparable} contract 145 * @see List#sort(Comparator) 146 */ 147 @SuppressWarnings("unchecked") 148 public static <T extends Comparable<? super T>> void sort(List<T> list) { 149 list.sort(null); 150 } 151 152 // Android-changed: Warn about Collections.sort() being built on top 153 // of List.sort() when it used to be the other way round in Nougat. 154 /** 155 * Sorts the specified list according to the order induced by the 156 * specified comparator. All elements in the list must be <i>mutually 157 * comparable</i> using the specified comparator (that is, 158 * {@code c.compare(e1, e2)} must not throw a {@code ClassCastException} 159 * for any elements {@code e1} and {@code e2} in the list). 160 * 161 * <p>This sort is guaranteed to be <i>stable</i>: equal elements will 162 * not be reordered as a result of the sort. 163 * 164 * <p>The specified list must be modifiable, but need not be resizable. 165 * 166 * @implNote 167 * This implementation defers to the {@link List#sort(Comparator)} 168 * method using the specified list and comparator. 169 * Note that in Android 7 (Nougat), {@code Collections.sort()} used to 170 * be implemented on top of {@link List#toArray()}, 171 * {@link ListIterator#next()} and {@link ListIterator#set(Object)}. 172 * 173 * @param <T> the class of the objects in the list 174 * @param list the list to be sorted. 175 * @param c the comparator to determine the order of the list. A 176 * {@code null} value indicates that the elements' <i>natural 177 * ordering</i> should be used. 178 * @throws ClassCastException if the list contains elements that are not 179 * <i>mutually comparable</i> using the specified comparator. 180 * @throws UnsupportedOperationException if the specified list's 181 * list-iterator does not support the {@code set} operation. 182 * @throws IllegalArgumentException (optional) if the comparator is 183 * found to violate the {@link Comparator} contract 184 * @see List#sort(Comparator) 185 */ 186 @SuppressWarnings({"unchecked", "rawtypes"}) 187 public static <T> void sort(List<T> list, Comparator<? super T> c) { 188 list.sort(c); 189 } 190 191 192 /** 193 * Searches the specified list for the specified object using the binary 194 * search algorithm. The list must be sorted into ascending order 195 * according to the {@linkplain Comparable natural ordering} of its 196 * elements (as by the {@link #sort(List)} method) prior to making this 197 * call. If it is not sorted, the results are undefined. If the list 198 * contains multiple elements equal to the specified object, there is no 199 * guarantee which one will be found. 200 * 201 * <p>This method runs in log(n) time for a "random access" list (which 202 * provides near-constant-time positional access). If the specified list 203 * does not implement the {@link RandomAccess} interface and is large, 204 * this method will do an iterator-based binary search that performs 205 * O(n) link traversals and O(log n) element comparisons. 206 * 207 * @param <T> the class of the objects in the list 208 * @param list the list to be searched. 209 * @param key the key to be searched for. 210 * @return the index of the search key, if it is contained in the list; 211 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The 212 * <i>insertion point</i> is defined as the point at which the 213 * key would be inserted into the list: the index of the first 214 * element greater than the key, or <tt>list.size()</tt> if all 215 * elements in the list are less than the specified key. Note 216 * that this guarantees that the return value will be >= 0 if 217 * and only if the key is found. 218 * @throws ClassCastException if the list contains elements that are not 219 * <i>mutually comparable</i> (for example, strings and 220 * integers), or the search key is not mutually comparable 221 * with the elements of the list. 222 */ 223 public static <T> 224 int binarySearch(List<? extends Comparable<? super T>> list, T key) { 225 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) 226 return Collections.indexedBinarySearch(list, key); 227 else 228 return Collections.iteratorBinarySearch(list, key); 229 } 230 231 private static <T> 232 int indexedBinarySearch(List<? extends Comparable<? super T>> list, T key) { 233 int low = 0; 234 int high = list.size()-1; 235 236 while (low <= high) { 237 int mid = (low + high) >>> 1; 238 Comparable<? super T> midVal = list.get(mid); 239 int cmp = midVal.compareTo(key); 240 241 if (cmp < 0) 242 low = mid + 1; 243 else if (cmp > 0) 244 high = mid - 1; 245 else 246 return mid; // key found 247 } 248 return -(low + 1); // key not found 249 } 250 251 private static <T> 252 int iteratorBinarySearch(List<? extends Comparable<? super T>> list, T key) 253 { 254 int low = 0; 255 int high = list.size()-1; 256 ListIterator<? extends Comparable<? super T>> i = list.listIterator(); 257 258 while (low <= high) { 259 int mid = (low + high) >>> 1; 260 Comparable<? super T> midVal = get(i, mid); 261 int cmp = midVal.compareTo(key); 262 263 if (cmp < 0) 264 low = mid + 1; 265 else if (cmp > 0) 266 high = mid - 1; 267 else 268 return mid; // key found 269 } 270 return -(low + 1); // key not found 271 } 272 273 /** 274 * Gets the ith element from the given list by repositioning the specified 275 * list listIterator. 276 */ 277 private static <T> T get(ListIterator<? extends T> i, int index) { 278 T obj = null; 279 int pos = i.nextIndex(); 280 if (pos <= index) { 281 do { 282 obj = i.next(); 283 } while (pos++ < index); 284 } else { 285 do { 286 obj = i.previous(); 287 } while (--pos > index); 288 } 289 return obj; 290 } 291 292 /** 293 * Searches the specified list for the specified object using the binary 294 * search algorithm. The list must be sorted into ascending order 295 * according to the specified comparator (as by the 296 * {@link #sort(List, Comparator) sort(List, Comparator)} 297 * method), prior to making this call. If it is 298 * not sorted, the results are undefined. If the list contains multiple 299 * elements equal to the specified object, there is no guarantee which one 300 * will be found. 301 * 302 * <p>This method runs in log(n) time for a "random access" list (which 303 * provides near-constant-time positional access). If the specified list 304 * does not implement the {@link RandomAccess} interface and is large, 305 * this method will do an iterator-based binary search that performs 306 * O(n) link traversals and O(log n) element comparisons. 307 * 308 * @param <T> the class of the objects in the list 309 * @param list the list to be searched. 310 * @param key the key to be searched for. 311 * @param c the comparator by which the list is ordered. 312 * A <tt>null</tt> value indicates that the elements' 313 * {@linkplain Comparable natural ordering} should be used. 314 * @return the index of the search key, if it is contained in the list; 315 * otherwise, <tt>(-(<i>insertion point</i>) - 1)</tt>. The 316 * <i>insertion point</i> is defined as the point at which the 317 * key would be inserted into the list: the index of the first 318 * element greater than the key, or <tt>list.size()</tt> if all 319 * elements in the list are less than the specified key. Note 320 * that this guarantees that the return value will be >= 0 if 321 * and only if the key is found. 322 * @throws ClassCastException if the list contains elements that are not 323 * <i>mutually comparable</i> using the specified comparator, 324 * or the search key is not mutually comparable with the 325 * elements of the list using this comparator. 326 */ 327 @SuppressWarnings("unchecked") 328 public static <T> int binarySearch(List<? extends T> list, T key, Comparator<? super T> c) { 329 if (c==null) 330 return binarySearch((List<? extends Comparable<? super T>>) list, key); 331 332 if (list instanceof RandomAccess || list.size()<BINARYSEARCH_THRESHOLD) 333 return Collections.indexedBinarySearch(list, key, c); 334 else 335 return Collections.iteratorBinarySearch(list, key, c); 336 } 337 338 private static <T> int indexedBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { 339 int low = 0; 340 int high = l.size()-1; 341 342 while (low <= high) { 343 int mid = (low + high) >>> 1; 344 T midVal = l.get(mid); 345 int cmp = c.compare(midVal, key); 346 347 if (cmp < 0) 348 low = mid + 1; 349 else if (cmp > 0) 350 high = mid - 1; 351 else 352 return mid; // key found 353 } 354 return -(low + 1); // key not found 355 } 356 357 private static <T> int iteratorBinarySearch(List<? extends T> l, T key, Comparator<? super T> c) { 358 int low = 0; 359 int high = l.size()-1; 360 ListIterator<? extends T> i = l.listIterator(); 361 362 while (low <= high) { 363 int mid = (low + high) >>> 1; 364 T midVal = get(i, mid); 365 int cmp = c.compare(midVal, key); 366 367 if (cmp < 0) 368 low = mid + 1; 369 else if (cmp > 0) 370 high = mid - 1; 371 else 372 return mid; // key found 373 } 374 return -(low + 1); // key not found 375 } 376 377 /** 378 * Reverses the order of the elements in the specified list.<p> 379 * 380 * This method runs in linear time. 381 * 382 * @param list the list whose elements are to be reversed. 383 * @throws UnsupportedOperationException if the specified list or 384 * its list-iterator does not support the <tt>set</tt> operation. 385 */ 386 @SuppressWarnings({"rawtypes", "unchecked"}) 387 public static void reverse(List<?> list) { 388 int size = list.size(); 389 if (size < REVERSE_THRESHOLD || list instanceof RandomAccess) { 390 for (int i=0, mid=size>>1, j=size-1; i<mid; i++, j--) 391 swap(list, i, j); 392 } else { 393 // instead of using a raw type here, it's possible to capture 394 // the wildcard but it will require a call to a supplementary 395 // private method 396 ListIterator fwd = list.listIterator(); 397 ListIterator rev = list.listIterator(size); 398 for (int i=0, mid=list.size()>>1; i<mid; i++) { 399 Object tmp = fwd.next(); 400 fwd.set(rev.previous()); 401 rev.set(tmp); 402 } 403 } 404 } 405 406 /** 407 * Randomly permutes the specified list using a default source of 408 * randomness. All permutations occur with approximately equal 409 * likelihood. 410 * 411 * <p>The hedge "approximately" is used in the foregoing description because 412 * default source of randomness is only approximately an unbiased source 413 * of independently chosen bits. If it were a perfect source of randomly 414 * chosen bits, then the algorithm would choose permutations with perfect 415 * uniformity. 416 * 417 * <p>This implementation traverses the list backwards, from the last 418 * element up to the second, repeatedly swapping a randomly selected element 419 * into the "current position". Elements are randomly selected from the 420 * portion of the list that runs from the first element to the current 421 * position, inclusive. 422 * 423 * <p>This method runs in linear time. If the specified list does not 424 * implement the {@link RandomAccess} interface and is large, this 425 * implementation dumps the specified list into an array before shuffling 426 * it, and dumps the shuffled array back into the list. This avoids the 427 * quadratic behavior that would result from shuffling a "sequential 428 * access" list in place. 429 * 430 * @param list the list to be shuffled. 431 * @throws UnsupportedOperationException if the specified list or 432 * its list-iterator does not support the <tt>set</tt> operation. 433 */ 434 public static void shuffle(List<?> list) { 435 Random rnd = r; 436 if (rnd == null) 437 r = rnd = new Random(); // harmless race. 438 shuffle(list, rnd); 439 } 440 441 private static Random r; 442 443 /** 444 * Randomly permute the specified list using the specified source of 445 * randomness. All permutations occur with equal likelihood 446 * assuming that the source of randomness is fair.<p> 447 * 448 * This implementation traverses the list backwards, from the last element 449 * up to the second, repeatedly swapping a randomly selected element into 450 * the "current position". Elements are randomly selected from the 451 * portion of the list that runs from the first element to the current 452 * position, inclusive.<p> 453 * 454 * This method runs in linear time. If the specified list does not 455 * implement the {@link RandomAccess} interface and is large, this 456 * implementation dumps the specified list into an array before shuffling 457 * it, and dumps the shuffled array back into the list. This avoids the 458 * quadratic behavior that would result from shuffling a "sequential 459 * access" list in place. 460 * 461 * @param list the list to be shuffled. 462 * @param rnd the source of randomness to use to shuffle the list. 463 * @throws UnsupportedOperationException if the specified list or its 464 * list-iterator does not support the <tt>set</tt> operation. 465 */ 466 @SuppressWarnings({"rawtypes", "unchecked"}) 467 public static void shuffle(List<?> list, Random rnd) { 468 int size = list.size(); 469 if (size < SHUFFLE_THRESHOLD || list instanceof RandomAccess) { 470 for (int i=size; i>1; i--) 471 swap(list, i-1, rnd.nextInt(i)); 472 } else { 473 Object arr[] = list.toArray(); 474 475 // Shuffle array 476 for (int i=size; i>1; i--) 477 swap(arr, i-1, rnd.nextInt(i)); 478 479 // Dump array back into list 480 // instead of using a raw type here, it's possible to capture 481 // the wildcard but it will require a call to a supplementary 482 // private method 483 ListIterator it = list.listIterator(); 484 for (int i=0; i<arr.length; i++) { 485 it.next(); 486 it.set(arr[i]); 487 } 488 } 489 } 490 491 /** 492 * Swaps the elements at the specified positions in the specified list. 493 * (If the specified positions are equal, invoking this method leaves 494 * the list unchanged.) 495 * 496 * @param list The list in which to swap elements. 497 * @param i the index of one element to be swapped. 498 * @param j the index of the other element to be swapped. 499 * @throws IndexOutOfBoundsException if either <tt>i</tt> or <tt>j</tt> 500 * is out of range (i < 0 || i >= list.size() 501 * || j < 0 || j >= list.size()). 502 * @since 1.4 503 */ 504 @SuppressWarnings({"rawtypes", "unchecked"}) 505 public static void swap(List<?> list, int i, int j) { 506 // instead of using a raw type here, it's possible to capture 507 // the wildcard but it will require a call to a supplementary 508 // private method 509 final List l = list; 510 l.set(i, l.set(j, l.get(i))); 511 } 512 513 /** 514 * Swaps the two specified elements in the specified array. 515 */ 516 private static void swap(Object[] arr, int i, int j) { 517 Object tmp = arr[i]; 518 arr[i] = arr[j]; 519 arr[j] = tmp; 520 } 521 522 /** 523 * Replaces all of the elements of the specified list with the specified 524 * element. <p> 525 * 526 * This method runs in linear time. 527 * 528 * @param <T> the class of the objects in the list 529 * @param list the list to be filled with the specified element. 530 * @param obj The element with which to fill the specified list. 531 * @throws UnsupportedOperationException if the specified list or its 532 * list-iterator does not support the <tt>set</tt> operation. 533 */ 534 public static <T> void fill(List<? super T> list, T obj) { 535 int size = list.size(); 536 537 if (size < FILL_THRESHOLD || list instanceof RandomAccess) { 538 for (int i=0; i<size; i++) 539 list.set(i, obj); 540 } else { 541 ListIterator<? super T> itr = list.listIterator(); 542 for (int i=0; i<size; i++) { 543 itr.next(); 544 itr.set(obj); 545 } 546 } 547 } 548 549 /** 550 * Copies all of the elements from one list into another. After the 551 * operation, the index of each copied element in the destination list 552 * will be identical to its index in the source list. The destination 553 * list must be at least as long as the source list. If it is longer, the 554 * remaining elements in the destination list are unaffected. <p> 555 * 556 * This method runs in linear time. 557 * 558 * @param <T> the class of the objects in the lists 559 * @param dest The destination list. 560 * @param src The source list. 561 * @throws IndexOutOfBoundsException if the destination list is too small 562 * to contain the entire source List. 563 * @throws UnsupportedOperationException if the destination list's 564 * list-iterator does not support the <tt>set</tt> operation. 565 */ 566 public static <T> void copy(List<? super T> dest, List<? extends T> src) { 567 int srcSize = src.size(); 568 if (srcSize > dest.size()) 569 throw new IndexOutOfBoundsException("Source does not fit in dest"); 570 571 if (srcSize < COPY_THRESHOLD || 572 (src instanceof RandomAccess && dest instanceof RandomAccess)) { 573 for (int i=0; i<srcSize; i++) 574 dest.set(i, src.get(i)); 575 } else { 576 ListIterator<? super T> di=dest.listIterator(); 577 ListIterator<? extends T> si=src.listIterator(); 578 for (int i=0; i<srcSize; i++) { 579 di.next(); 580 di.set(si.next()); 581 } 582 } 583 } 584 585 /** 586 * Returns the minimum element of the given collection, according to the 587 * <i>natural ordering</i> of its elements. All elements in the 588 * collection must implement the <tt>Comparable</tt> interface. 589 * Furthermore, all elements in the collection must be <i>mutually 590 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a 591 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 592 * <tt>e2</tt> in the collection).<p> 593 * 594 * This method iterates over the entire collection, hence it requires 595 * time proportional to the size of the collection. 596 * 597 * @param <T> the class of the objects in the collection 598 * @param coll the collection whose minimum element is to be determined. 599 * @return the minimum element of the given collection, according 600 * to the <i>natural ordering</i> of its elements. 601 * @throws ClassCastException if the collection contains elements that are 602 * not <i>mutually comparable</i> (for example, strings and 603 * integers). 604 * @throws NoSuchElementException if the collection is empty. 605 * @see Comparable 606 */ 607 public static <T extends Object & Comparable<? super T>> T min(Collection<? extends T> coll) { 608 Iterator<? extends T> i = coll.iterator(); 609 T candidate = i.next(); 610 611 while (i.hasNext()) { 612 T next = i.next(); 613 if (next.compareTo(candidate) < 0) 614 candidate = next; 615 } 616 return candidate; 617 } 618 619 /** 620 * Returns the minimum element of the given collection, according to the 621 * order induced by the specified comparator. All elements in the 622 * collection must be <i>mutually comparable</i> by the specified 623 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a 624 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 625 * <tt>e2</tt> in the collection).<p> 626 * 627 * This method iterates over the entire collection, hence it requires 628 * time proportional to the size of the collection. 629 * 630 * @param <T> the class of the objects in the collection 631 * @param coll the collection whose minimum element is to be determined. 632 * @param comp the comparator with which to determine the minimum element. 633 * A <tt>null</tt> value indicates that the elements' <i>natural 634 * ordering</i> should be used. 635 * @return the minimum element of the given collection, according 636 * to the specified comparator. 637 * @throws ClassCastException if the collection contains elements that are 638 * not <i>mutually comparable</i> using the specified comparator. 639 * @throws NoSuchElementException if the collection is empty. 640 * @see Comparable 641 */ 642 @SuppressWarnings({"unchecked", "rawtypes"}) 643 public static <T> T min(Collection<? extends T> coll, Comparator<? super T> comp) { 644 if (comp==null) 645 return (T)min((Collection) coll); 646 647 Iterator<? extends T> i = coll.iterator(); 648 T candidate = i.next(); 649 650 while (i.hasNext()) { 651 T next = i.next(); 652 if (comp.compare(next, candidate) < 0) 653 candidate = next; 654 } 655 return candidate; 656 } 657 658 /** 659 * Returns the maximum element of the given collection, according to the 660 * <i>natural ordering</i> of its elements. All elements in the 661 * collection must implement the <tt>Comparable</tt> interface. 662 * Furthermore, all elements in the collection must be <i>mutually 663 * comparable</i> (that is, <tt>e1.compareTo(e2)</tt> must not throw a 664 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 665 * <tt>e2</tt> in the collection).<p> 666 * 667 * This method iterates over the entire collection, hence it requires 668 * time proportional to the size of the collection. 669 * 670 * @param <T> the class of the objects in the collection 671 * @param coll the collection whose maximum element is to be determined. 672 * @return the maximum element of the given collection, according 673 * to the <i>natural ordering</i> of its elements. 674 * @throws ClassCastException if the collection contains elements that are 675 * not <i>mutually comparable</i> (for example, strings and 676 * integers). 677 * @throws NoSuchElementException if the collection is empty. 678 * @see Comparable 679 */ 680 public static <T extends Object & Comparable<? super T>> T max(Collection<? extends T> coll) { 681 Iterator<? extends T> i = coll.iterator(); 682 T candidate = i.next(); 683 684 while (i.hasNext()) { 685 T next = i.next(); 686 if (next.compareTo(candidate) > 0) 687 candidate = next; 688 } 689 return candidate; 690 } 691 692 /** 693 * Returns the maximum element of the given collection, according to the 694 * order induced by the specified comparator. All elements in the 695 * collection must be <i>mutually comparable</i> by the specified 696 * comparator (that is, <tt>comp.compare(e1, e2)</tt> must not throw a 697 * <tt>ClassCastException</tt> for any elements <tt>e1</tt> and 698 * <tt>e2</tt> in the collection).<p> 699 * 700 * This method iterates over the entire collection, hence it requires 701 * time proportional to the size of the collection. 702 * 703 * @param <T> the class of the objects in the collection 704 * @param coll the collection whose maximum element is to be determined. 705 * @param comp the comparator with which to determine the maximum element. 706 * A <tt>null</tt> value indicates that the elements' <i>natural 707 * ordering</i> should be used. 708 * @return the maximum element of the given collection, according 709 * to the specified comparator. 710 * @throws ClassCastException if the collection contains elements that are 711 * not <i>mutually comparable</i> using the specified comparator. 712 * @throws NoSuchElementException if the collection is empty. 713 * @see Comparable 714 */ 715 @SuppressWarnings({"unchecked", "rawtypes"}) 716 public static <T> T max(Collection<? extends T> coll, Comparator<? super T> comp) { 717 if (comp==null) 718 return (T)max((Collection) coll); 719 720 Iterator<? extends T> i = coll.iterator(); 721 T candidate = i.next(); 722 723 while (i.hasNext()) { 724 T next = i.next(); 725 if (comp.compare(next, candidate) > 0) 726 candidate = next; 727 } 728 return candidate; 729 } 730 731 /** 732 * Rotates the elements in the specified list by the specified distance. 733 * After calling this method, the element at index <tt>i</tt> will be 734 * the element previously at index <tt>(i - distance)</tt> mod 735 * <tt>list.size()</tt>, for all values of <tt>i</tt> between <tt>0</tt> 736 * and <tt>list.size()-1</tt>, inclusive. (This method has no effect on 737 * the size of the list.) 738 * 739 * <p>For example, suppose <tt>list</tt> comprises<tt> [t, a, n, k, s]</tt>. 740 * After invoking <tt>Collections.rotate(list, 1)</tt> (or 741 * <tt>Collections.rotate(list, -4)</tt>), <tt>list</tt> will comprise 742 * <tt>[s, t, a, n, k]</tt>. 743 * 744 * <p>Note that this method can usefully be applied to sublists to 745 * move one or more elements within a list while preserving the 746 * order of the remaining elements. For example, the following idiom 747 * moves the element at index <tt>j</tt> forward to position 748 * <tt>k</tt> (which must be greater than or equal to <tt>j</tt>): 749 * <pre> 750 * Collections.rotate(list.subList(j, k+1), -1); 751 * </pre> 752 * To make this concrete, suppose <tt>list</tt> comprises 753 * <tt>[a, b, c, d, e]</tt>. To move the element at index <tt>1</tt> 754 * (<tt>b</tt>) forward two positions, perform the following invocation: 755 * <pre> 756 * Collections.rotate(l.subList(1, 4), -1); 757 * </pre> 758 * The resulting list is <tt>[a, c, d, b, e]</tt>. 759 * 760 * <p>To move more than one element forward, increase the absolute value 761 * of the rotation distance. To move elements backward, use a positive 762 * shift distance. 763 * 764 * <p>If the specified list is small or implements the {@link 765 * RandomAccess} interface, this implementation exchanges the first 766 * element into the location it should go, and then repeatedly exchanges 767 * the displaced element into the location it should go until a displaced 768 * element is swapped into the first element. If necessary, the process 769 * is repeated on the second and successive elements, until the rotation 770 * is complete. If the specified list is large and doesn't implement the 771 * <tt>RandomAccess</tt> interface, this implementation breaks the 772 * list into two sublist views around index <tt>-distance mod size</tt>. 773 * Then the {@link #reverse(List)} method is invoked on each sublist view, 774 * and finally it is invoked on the entire list. For a more complete 775 * description of both algorithms, see Section 2.3 of Jon Bentley's 776 * <i>Programming Pearls</i> (Addison-Wesley, 1986). 777 * 778 * @param list the list to be rotated. 779 * @param distance the distance to rotate the list. There are no 780 * constraints on this value; it may be zero, negative, or 781 * greater than <tt>list.size()</tt>. 782 * @throws UnsupportedOperationException if the specified list or 783 * its list-iterator does not support the <tt>set</tt> operation. 784 * @since 1.4 785 */ 786 public static void rotate(List<?> list, int distance) { 787 if (list instanceof RandomAccess || list.size() < ROTATE_THRESHOLD) 788 rotate1(list, distance); 789 else 790 rotate2(list, distance); 791 } 792 793 private static <T> void rotate1(List<T> list, int distance) { 794 int size = list.size(); 795 if (size == 0) 796 return; 797 distance = distance % size; 798 if (distance < 0) 799 distance += size; 800 if (distance == 0) 801 return; 802 803 for (int cycleStart = 0, nMoved = 0; nMoved != size; cycleStart++) { 804 T displaced = list.get(cycleStart); 805 int i = cycleStart; 806 do { 807 i += distance; 808 if (i >= size) 809 i -= size; 810 displaced = list.set(i, displaced); 811 nMoved ++; 812 } while (i != cycleStart); 813 } 814 } 815 816 private static void rotate2(List<?> list, int distance) { 817 int size = list.size(); 818 if (size == 0) 819 return; 820 int mid = -distance % size; 821 if (mid < 0) 822 mid += size; 823 if (mid == 0) 824 return; 825 826 reverse(list.subList(0, mid)); 827 reverse(list.subList(mid, size)); 828 reverse(list); 829 } 830 831 /** 832 * Replaces all occurrences of one specified value in a list with another. 833 * More formally, replaces with <tt>newVal</tt> each element <tt>e</tt> 834 * in <tt>list</tt> such that 835 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. 836 * (This method has no effect on the size of the list.) 837 * 838 * @param <T> the class of the objects in the list 839 * @param list the list in which replacement is to occur. 840 * @param oldVal the old value to be replaced. 841 * @param newVal the new value with which <tt>oldVal</tt> is to be 842 * replaced. 843 * @return <tt>true</tt> if <tt>list</tt> contained one or more elements 844 * <tt>e</tt> such that 845 * <tt>(oldVal==null ? e==null : oldVal.equals(e))</tt>. 846 * @throws UnsupportedOperationException if the specified list or 847 * its list-iterator does not support the <tt>set</tt> operation. 848 * @since 1.4 849 */ 850 public static <T> boolean replaceAll(List<T> list, T oldVal, T newVal) { 851 boolean result = false; 852 int size = list.size(); 853 if (size < REPLACEALL_THRESHOLD || list instanceof RandomAccess) { 854 if (oldVal==null) { 855 for (int i=0; i<size; i++) { 856 if (list.get(i)==null) { 857 list.set(i, newVal); 858 result = true; 859 } 860 } 861 } else { 862 for (int i=0; i<size; i++) { 863 if (oldVal.equals(list.get(i))) { 864 list.set(i, newVal); 865 result = true; 866 } 867 } 868 } 869 } else { 870 ListIterator<T> itr=list.listIterator(); 871 if (oldVal==null) { 872 for (int i=0; i<size; i++) { 873 if (itr.next()==null) { 874 itr.set(newVal); 875 result = true; 876 } 877 } 878 } else { 879 for (int i=0; i<size; i++) { 880 if (oldVal.equals(itr.next())) { 881 itr.set(newVal); 882 result = true; 883 } 884 } 885 } 886 } 887 return result; 888 } 889 890 /** 891 * Returns the starting position of the first occurrence of the specified 892 * target list within the specified source list, or -1 if there is no 893 * such occurrence. More formally, returns the lowest index <tt>i</tt> 894 * such that {@code source.subList(i, i+target.size()).equals(target)}, 895 * or -1 if there is no such index. (Returns -1 if 896 * {@code target.size() > source.size()}) 897 * 898 * <p>This implementation uses the "brute force" technique of scanning 899 * over the source list, looking for a match with the target at each 900 * location in turn. 901 * 902 * @param source the list in which to search for the first occurrence 903 * of <tt>target</tt>. 904 * @param target the list to search for as a subList of <tt>source</tt>. 905 * @return the starting position of the first occurrence of the specified 906 * target list within the specified source list, or -1 if there 907 * is no such occurrence. 908 * @since 1.4 909 */ 910 public static int indexOfSubList(List<?> source, List<?> target) { 911 int sourceSize = source.size(); 912 int targetSize = target.size(); 913 int maxCandidate = sourceSize - targetSize; 914 915 if (sourceSize < INDEXOFSUBLIST_THRESHOLD || 916 (source instanceof RandomAccess&&target instanceof RandomAccess)) { 917 nextCand: 918 for (int candidate = 0; candidate <= maxCandidate; candidate++) { 919 for (int i=0, j=candidate; i<targetSize; i++, j++) 920 if (!eq(target.get(i), source.get(j))) 921 continue nextCand; // Element mismatch, try next cand 922 return candidate; // All elements of candidate matched target 923 } 924 } else { // Iterator version of above algorithm 925 ListIterator<?> si = source.listIterator(); 926 nextCand: 927 for (int candidate = 0; candidate <= maxCandidate; candidate++) { 928 ListIterator<?> ti = target.listIterator(); 929 for (int i=0; i<targetSize; i++) { 930 if (!eq(ti.next(), si.next())) { 931 // Back up source iterator to next candidate 932 for (int j=0; j<i; j++) 933 si.previous(); 934 continue nextCand; 935 } 936 } 937 return candidate; 938 } 939 } 940 return -1; // No candidate matched the target 941 } 942 943 /** 944 * Returns the starting position of the last occurrence of the specified 945 * target list within the specified source list, or -1 if there is no such 946 * occurrence. More formally, returns the highest index <tt>i</tt> 947 * such that {@code source.subList(i, i+target.size()).equals(target)}, 948 * or -1 if there is no such index. (Returns -1 if 949 * {@code target.size() > source.size()}) 950 * 951 * <p>This implementation uses the "brute force" technique of iterating 952 * over the source list, looking for a match with the target at each 953 * location in turn. 954 * 955 * @param source the list in which to search for the last occurrence 956 * of <tt>target</tt>. 957 * @param target the list to search for as a subList of <tt>source</tt>. 958 * @return the starting position of the last occurrence of the specified 959 * target list within the specified source list, or -1 if there 960 * is no such occurrence. 961 * @since 1.4 962 */ 963 public static int lastIndexOfSubList(List<?> source, List<?> target) { 964 int sourceSize = source.size(); 965 int targetSize = target.size(); 966 int maxCandidate = sourceSize - targetSize; 967 968 if (sourceSize < INDEXOFSUBLIST_THRESHOLD || 969 source instanceof RandomAccess) { // Index access version 970 nextCand: 971 for (int candidate = maxCandidate; candidate >= 0; candidate--) { 972 for (int i=0, j=candidate; i<targetSize; i++, j++) 973 if (!eq(target.get(i), source.get(j))) 974 continue nextCand; // Element mismatch, try next cand 975 return candidate; // All elements of candidate matched target 976 } 977 } else { // Iterator version of above algorithm 978 if (maxCandidate < 0) 979 return -1; 980 ListIterator<?> si = source.listIterator(maxCandidate); 981 nextCand: 982 for (int candidate = maxCandidate; candidate >= 0; candidate--) { 983 ListIterator<?> ti = target.listIterator(); 984 for (int i=0; i<targetSize; i++) { 985 if (!eq(ti.next(), si.next())) { 986 if (candidate != 0) { 987 // Back up source iterator to next candidate 988 for (int j=0; j<=i+1; j++) 989 si.previous(); 990 } 991 continue nextCand; 992 } 993 } 994 return candidate; 995 } 996 } 997 return -1; // No candidate matched the target 998 } 999 1000 1001 // Unmodifiable Wrappers 1002 1003 /** 1004 * Returns an unmodifiable view of the specified collection. This method 1005 * allows modules to provide users with "read-only" access to internal 1006 * collections. Query operations on the returned collection "read through" 1007 * to the specified collection, and attempts to modify the returned 1008 * collection, whether direct or via its iterator, result in an 1009 * <tt>UnsupportedOperationException</tt>.<p> 1010 * 1011 * The returned collection does <i>not</i> pass the hashCode and equals 1012 * operations through to the backing collection, but relies on 1013 * <tt>Object</tt>'s <tt>equals</tt> and <tt>hashCode</tt> methods. This 1014 * is necessary to preserve the contracts of these operations in the case 1015 * that the backing collection is a set or a list.<p> 1016 * 1017 * The returned collection will be serializable if the specified collection 1018 * is serializable. 1019 * 1020 * @param <T> the class of the objects in the collection 1021 * @param c the collection for which an unmodifiable view is to be 1022 * returned. 1023 * @return an unmodifiable view of the specified collection. 1024 */ 1025 public static <T> Collection<T> unmodifiableCollection(Collection<? extends T> c) { 1026 return new UnmodifiableCollection<>(c); 1027 } 1028 1029 /** 1030 * @serial include 1031 */ 1032 static class UnmodifiableCollection<E> implements Collection<E>, Serializable { 1033 private static final long serialVersionUID = 1820017752578914078L; 1034 1035 final Collection<? extends E> c; 1036 1037 UnmodifiableCollection(Collection<? extends E> c) { 1038 if (c==null) 1039 throw new NullPointerException(); 1040 this.c = c; 1041 } 1042 1043 public int size() {return c.size();} 1044 public boolean isEmpty() {return c.isEmpty();} 1045 public boolean contains(Object o) {return c.contains(o);} 1046 public Object[] toArray() {return c.toArray();} 1047 public <T> T[] toArray(T[] a) {return c.toArray(a);} 1048 public String toString() {return c.toString();} 1049 1050 public Iterator<E> iterator() { 1051 return new Iterator<E>() { 1052 private final Iterator<? extends E> i = c.iterator(); 1053 1054 public boolean hasNext() {return i.hasNext();} 1055 public E next() {return i.next();} 1056 public void remove() { 1057 throw new UnsupportedOperationException(); 1058 } 1059 @Override 1060 public void forEachRemaining(Consumer<? super E> action) { 1061 // Use backing collection version 1062 i.forEachRemaining(action); 1063 } 1064 }; 1065 } 1066 1067 public boolean add(E e) { 1068 throw new UnsupportedOperationException(); 1069 } 1070 public boolean remove(Object o) { 1071 throw new UnsupportedOperationException(); 1072 } 1073 1074 public boolean containsAll(Collection<?> coll) { 1075 return c.containsAll(coll); 1076 } 1077 public boolean addAll(Collection<? extends E> coll) { 1078 throw new UnsupportedOperationException(); 1079 } 1080 public boolean removeAll(Collection<?> coll) { 1081 throw new UnsupportedOperationException(); 1082 } 1083 public boolean retainAll(Collection<?> coll) { 1084 throw new UnsupportedOperationException(); 1085 } 1086 public void clear() { 1087 throw new UnsupportedOperationException(); 1088 } 1089 1090 // Override default methods in Collection 1091 @Override 1092 public void forEach(Consumer<? super E> action) { 1093 c.forEach(action); 1094 } 1095 @Override 1096 public boolean removeIf(Predicate<? super E> filter) { 1097 throw new UnsupportedOperationException(); 1098 } 1099 @SuppressWarnings("unchecked") 1100 @Override 1101 public Spliterator<E> spliterator() { 1102 return (Spliterator<E>)c.spliterator(); 1103 } 1104 @SuppressWarnings("unchecked") 1105 @Override 1106 public Stream<E> stream() { 1107 return (Stream<E>)c.stream(); 1108 } 1109 @SuppressWarnings("unchecked") 1110 @Override 1111 public Stream<E> parallelStream() { 1112 return (Stream<E>)c.parallelStream(); 1113 } 1114 } 1115 1116 /** 1117 * Returns an unmodifiable view of the specified set. This method allows 1118 * modules to provide users with "read-only" access to internal sets. 1119 * Query operations on the returned set "read through" to the specified 1120 * set, and attempts to modify the returned set, whether direct or via its 1121 * iterator, result in an <tt>UnsupportedOperationException</tt>.<p> 1122 * 1123 * The returned set will be serializable if the specified set 1124 * is serializable. 1125 * 1126 * @param <T> the class of the objects in the set 1127 * @param s the set for which an unmodifiable view is to be returned. 1128 * @return an unmodifiable view of the specified set. 1129 */ 1130 public static <T> Set<T> unmodifiableSet(Set<? extends T> s) { 1131 return new UnmodifiableSet<>(s); 1132 } 1133 1134 /** 1135 * @serial include 1136 */ 1137 static class UnmodifiableSet<E> extends UnmodifiableCollection<E> 1138 implements Set<E>, Serializable { 1139 private static final long serialVersionUID = -9215047833775013803L; 1140 1141 UnmodifiableSet(Set<? extends E> s) {super(s);} 1142 public boolean equals(Object o) {return o == this || c.equals(o);} 1143 public int hashCode() {return c.hashCode();} 1144 } 1145 1146 /** 1147 * Returns an unmodifiable view of the specified sorted set. This method 1148 * allows modules to provide users with "read-only" access to internal 1149 * sorted sets. Query operations on the returned sorted set "read 1150 * through" to the specified sorted set. Attempts to modify the returned 1151 * sorted set, whether direct, via its iterator, or via its 1152 * <tt>subSet</tt>, <tt>headSet</tt>, or <tt>tailSet</tt> views, result in 1153 * an <tt>UnsupportedOperationException</tt>.<p> 1154 * 1155 * The returned sorted set will be serializable if the specified sorted set 1156 * is serializable. 1157 * 1158 * @param <T> the class of the objects in the set 1159 * @param s the sorted set for which an unmodifiable view is to be 1160 * returned. 1161 * @return an unmodifiable view of the specified sorted set. 1162 */ 1163 public static <T> SortedSet<T> unmodifiableSortedSet(SortedSet<T> s) { 1164 return new UnmodifiableSortedSet<>(s); 1165 } 1166 1167 /** 1168 * @serial include 1169 */ 1170 static class UnmodifiableSortedSet<E> 1171 extends UnmodifiableSet<E> 1172 implements SortedSet<E>, Serializable { 1173 private static final long serialVersionUID = -4929149591599911165L; 1174 private final SortedSet<E> ss; 1175 1176 UnmodifiableSortedSet(SortedSet<E> s) {super(s); ss = s;} 1177 1178 public Comparator<? super E> comparator() {return ss.comparator();} 1179 1180 public SortedSet<E> subSet(E fromElement, E toElement) { 1181 return new UnmodifiableSortedSet<>(ss.subSet(fromElement,toElement)); 1182 } 1183 public SortedSet<E> headSet(E toElement) { 1184 return new UnmodifiableSortedSet<>(ss.headSet(toElement)); 1185 } 1186 public SortedSet<E> tailSet(E fromElement) { 1187 return new UnmodifiableSortedSet<>(ss.tailSet(fromElement)); 1188 } 1189 1190 public E first() {return ss.first();} 1191 public E last() {return ss.last();} 1192 } 1193 1194 /** 1195 * Returns an unmodifiable view of the specified navigable set. This method 1196 * allows modules to provide users with "read-only" access to internal 1197 * navigable sets. Query operations on the returned navigable set "read 1198 * through" to the specified navigable set. Attempts to modify the returned 1199 * navigable set, whether direct, via its iterator, or via its 1200 * {@code subSet}, {@code headSet}, or {@code tailSet} views, result in 1201 * an {@code UnsupportedOperationException}.<p> 1202 * 1203 * The returned navigable set will be serializable if the specified 1204 * navigable set is serializable. 1205 * 1206 * @param <T> the class of the objects in the set 1207 * @param s the navigable set for which an unmodifiable view is to be 1208 * returned 1209 * @return an unmodifiable view of the specified navigable set 1210 * @since 1.8 1211 * @hide 1212 */ 1213 public static <T> NavigableSet<T> unmodifiableNavigableSet(NavigableSet<T> s) { 1214 return new UnmodifiableNavigableSet<>(s); 1215 } 1216 1217 /** 1218 * Wraps a navigable set and disables all of the mutative operations. 1219 * 1220 * @param <E> type of elements 1221 * @serial include 1222 */ 1223 static class UnmodifiableNavigableSet<E> 1224 extends UnmodifiableSortedSet<E> 1225 implements NavigableSet<E>, Serializable { 1226 1227 private static final long serialVersionUID = -6027448201786391929L; 1228 1229 /** 1230 * A singleton empty unmodifiable navigable set used for 1231 * {@link #emptyNavigableSet()}. 1232 * 1233 * @param <E> type of elements, if there were any, and bounds 1234 */ 1235 private static class EmptyNavigableSet<E> extends UnmodifiableNavigableSet<E> 1236 implements Serializable { 1237 private static final long serialVersionUID = -6291252904449939134L; 1238 1239 public EmptyNavigableSet() { 1240 super(new TreeSet<E>()); 1241 } 1242 1243 private Object readResolve() { return EMPTY_NAVIGABLE_SET; } 1244 } 1245 1246 @SuppressWarnings("rawtypes") 1247 private static final NavigableSet<?> EMPTY_NAVIGABLE_SET = 1248 new EmptyNavigableSet<>(); 1249 1250 /** 1251 * The instance we are protecting. 1252 */ 1253 private final NavigableSet<E> ns; 1254 1255 UnmodifiableNavigableSet(NavigableSet<E> s) {super(s); ns = s;} 1256 1257 public E lower(E e) { return ns.lower(e); } 1258 public E floor(E e) { return ns.floor(e); } 1259 public E ceiling(E e) { return ns.ceiling(e); } 1260 public E higher(E e) { return ns.higher(e); } 1261 public E pollFirst() { throw new UnsupportedOperationException(); } 1262 public E pollLast() { throw new UnsupportedOperationException(); } 1263 public NavigableSet<E> descendingSet() 1264 { return new UnmodifiableNavigableSet<>(ns.descendingSet()); } 1265 public Iterator<E> descendingIterator() 1266 { return descendingSet().iterator(); } 1267 1268 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 1269 return new UnmodifiableNavigableSet<>( 1270 ns.subSet(fromElement, fromInclusive, toElement, toInclusive)); 1271 } 1272 1273 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 1274 return new UnmodifiableNavigableSet<>( 1275 ns.headSet(toElement, inclusive)); 1276 } 1277 1278 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 1279 return new UnmodifiableNavigableSet<>( 1280 ns.tailSet(fromElement, inclusive)); 1281 } 1282 } 1283 1284 /** 1285 * Returns an unmodifiable view of the specified list. This method allows 1286 * modules to provide users with "read-only" access to internal 1287 * lists. Query operations on the returned list "read through" to the 1288 * specified list, and attempts to modify the returned list, whether 1289 * direct or via its iterator, result in an 1290 * <tt>UnsupportedOperationException</tt>.<p> 1291 * 1292 * The returned list will be serializable if the specified list 1293 * is serializable. Similarly, the returned list will implement 1294 * {@link RandomAccess} if the specified list does. 1295 * 1296 * @param <T> the class of the objects in the list 1297 * @param list the list for which an unmodifiable view is to be returned. 1298 * @return an unmodifiable view of the specified list. 1299 */ 1300 public static <T> List<T> unmodifiableList(List<? extends T> list) { 1301 return (list instanceof RandomAccess ? 1302 new UnmodifiableRandomAccessList<>(list) : 1303 new UnmodifiableList<>(list)); 1304 } 1305 1306 /** 1307 * @serial include 1308 */ 1309 static class UnmodifiableList<E> extends UnmodifiableCollection<E> 1310 implements List<E> { 1311 private static final long serialVersionUID = -283967356065247728L; 1312 1313 final List<? extends E> list; 1314 1315 UnmodifiableList(List<? extends E> list) { 1316 super(list); 1317 this.list = list; 1318 } 1319 1320 public boolean equals(Object o) {return o == this || list.equals(o);} 1321 public int hashCode() {return list.hashCode();} 1322 1323 public E get(int index) {return list.get(index);} 1324 public E set(int index, E element) { 1325 throw new UnsupportedOperationException(); 1326 } 1327 public void add(int index, E element) { 1328 throw new UnsupportedOperationException(); 1329 } 1330 public E remove(int index) { 1331 throw new UnsupportedOperationException(); 1332 } 1333 public int indexOf(Object o) {return list.indexOf(o);} 1334 public int lastIndexOf(Object o) {return list.lastIndexOf(o);} 1335 public boolean addAll(int index, Collection<? extends E> c) { 1336 throw new UnsupportedOperationException(); 1337 } 1338 1339 @Override 1340 public void replaceAll(UnaryOperator<E> operator) { 1341 throw new UnsupportedOperationException(); 1342 } 1343 @Override 1344 public void sort(Comparator<? super E> c) { 1345 throw new UnsupportedOperationException(); 1346 } 1347 1348 public ListIterator<E> listIterator() {return listIterator(0);} 1349 1350 public ListIterator<E> listIterator(final int index) { 1351 return new ListIterator<E>() { 1352 private final ListIterator<? extends E> i 1353 = list.listIterator(index); 1354 1355 public boolean hasNext() {return i.hasNext();} 1356 public E next() {return i.next();} 1357 public boolean hasPrevious() {return i.hasPrevious();} 1358 public E previous() {return i.previous();} 1359 public int nextIndex() {return i.nextIndex();} 1360 public int previousIndex() {return i.previousIndex();} 1361 1362 public void remove() { 1363 throw new UnsupportedOperationException(); 1364 } 1365 public void set(E e) { 1366 throw new UnsupportedOperationException(); 1367 } 1368 public void add(E e) { 1369 throw new UnsupportedOperationException(); 1370 } 1371 1372 @Override 1373 public void forEachRemaining(Consumer<? super E> action) { 1374 i.forEachRemaining(action); 1375 } 1376 }; 1377 } 1378 1379 public List<E> subList(int fromIndex, int toIndex) { 1380 return new UnmodifiableList<>(list.subList(fromIndex, toIndex)); 1381 } 1382 1383 /** 1384 * UnmodifiableRandomAccessList instances are serialized as 1385 * UnmodifiableList instances to allow them to be deserialized 1386 * in pre-1.4 JREs (which do not have UnmodifiableRandomAccessList). 1387 * This method inverts the transformation. As a beneficial 1388 * side-effect, it also grafts the RandomAccess marker onto 1389 * UnmodifiableList instances that were serialized in pre-1.4 JREs. 1390 * 1391 * Note: Unfortunately, UnmodifiableRandomAccessList instances 1392 * serialized in 1.4.1 and deserialized in 1.4 will become 1393 * UnmodifiableList instances, as this method was missing in 1.4. 1394 */ 1395 private Object readResolve() { 1396 return (list instanceof RandomAccess 1397 ? new UnmodifiableRandomAccessList<>(list) 1398 : this); 1399 } 1400 } 1401 1402 /** 1403 * @serial include 1404 */ 1405 static class UnmodifiableRandomAccessList<E> extends UnmodifiableList<E> 1406 implements RandomAccess 1407 { 1408 UnmodifiableRandomAccessList(List<? extends E> list) { 1409 super(list); 1410 } 1411 1412 public List<E> subList(int fromIndex, int toIndex) { 1413 return new UnmodifiableRandomAccessList<>( 1414 list.subList(fromIndex, toIndex)); 1415 } 1416 1417 private static final long serialVersionUID = -2542308836966382001L; 1418 1419 /** 1420 * Allows instances to be deserialized in pre-1.4 JREs (which do 1421 * not have UnmodifiableRandomAccessList). UnmodifiableList has 1422 * a readResolve method that inverts this transformation upon 1423 * deserialization. 1424 */ 1425 private Object writeReplace() { 1426 return new UnmodifiableList<>(list); 1427 } 1428 } 1429 1430 /** 1431 * Returns an unmodifiable view of the specified map. This method 1432 * allows modules to provide users with "read-only" access to internal 1433 * maps. Query operations on the returned map "read through" 1434 * to the specified map, and attempts to modify the returned 1435 * map, whether direct or via its collection views, result in an 1436 * <tt>UnsupportedOperationException</tt>.<p> 1437 * 1438 * The returned map will be serializable if the specified map 1439 * is serializable. 1440 * 1441 * @param <K> the class of the map keys 1442 * @param <V> the class of the map values 1443 * @param m the map for which an unmodifiable view is to be returned. 1444 * @return an unmodifiable view of the specified map. 1445 */ 1446 public static <K,V> Map<K,V> unmodifiableMap(Map<? extends K, ? extends V> m) { 1447 return new UnmodifiableMap<>(m); 1448 } 1449 1450 /** 1451 * @serial include 1452 */ 1453 private static class UnmodifiableMap<K,V> implements Map<K,V>, Serializable { 1454 private static final long serialVersionUID = -1034234728574286014L; 1455 1456 private final Map<? extends K, ? extends V> m; 1457 1458 UnmodifiableMap(Map<? extends K, ? extends V> m) { 1459 if (m==null) 1460 throw new NullPointerException(); 1461 this.m = m; 1462 } 1463 1464 public int size() {return m.size();} 1465 public boolean isEmpty() {return m.isEmpty();} 1466 public boolean containsKey(Object key) {return m.containsKey(key);} 1467 public boolean containsValue(Object val) {return m.containsValue(val);} 1468 public V get(Object key) {return m.get(key);} 1469 1470 public V put(K key, V value) { 1471 throw new UnsupportedOperationException(); 1472 } 1473 public V remove(Object key) { 1474 throw new UnsupportedOperationException(); 1475 } 1476 public void putAll(Map<? extends K, ? extends V> m) { 1477 throw new UnsupportedOperationException(); 1478 } 1479 public void clear() { 1480 throw new UnsupportedOperationException(); 1481 } 1482 1483 private transient Set<K> keySet; 1484 private transient Set<Map.Entry<K,V>> entrySet; 1485 private transient Collection<V> values; 1486 1487 public Set<K> keySet() { 1488 if (keySet==null) 1489 keySet = unmodifiableSet(m.keySet()); 1490 return keySet; 1491 } 1492 1493 public Set<Map.Entry<K,V>> entrySet() { 1494 if (entrySet==null) 1495 entrySet = new UnmodifiableEntrySet<>(m.entrySet()); 1496 return entrySet; 1497 } 1498 1499 public Collection<V> values() { 1500 if (values==null) 1501 values = unmodifiableCollection(m.values()); 1502 return values; 1503 } 1504 1505 public boolean equals(Object o) {return o == this || m.equals(o);} 1506 public int hashCode() {return m.hashCode();} 1507 public String toString() {return m.toString();} 1508 1509 // Override default methods in Map 1510 @Override 1511 @SuppressWarnings("unchecked") 1512 public V getOrDefault(Object k, V defaultValue) { 1513 // Safe cast as we don't change the value 1514 return ((Map<K, V>)m).getOrDefault(k, defaultValue); 1515 } 1516 1517 @Override 1518 public void forEach(BiConsumer<? super K, ? super V> action) { 1519 m.forEach(action); 1520 } 1521 1522 @Override 1523 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 1524 throw new UnsupportedOperationException(); 1525 } 1526 1527 @Override 1528 public V putIfAbsent(K key, V value) { 1529 throw new UnsupportedOperationException(); 1530 } 1531 1532 @Override 1533 public boolean remove(Object key, Object value) { 1534 throw new UnsupportedOperationException(); 1535 } 1536 1537 @Override 1538 public boolean replace(K key, V oldValue, V newValue) { 1539 throw new UnsupportedOperationException(); 1540 } 1541 1542 @Override 1543 public V replace(K key, V value) { 1544 throw new UnsupportedOperationException(); 1545 } 1546 1547 @Override 1548 public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) { 1549 throw new UnsupportedOperationException(); 1550 } 1551 1552 @Override 1553 public V computeIfPresent(K key, 1554 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 1555 throw new UnsupportedOperationException(); 1556 } 1557 1558 @Override 1559 public V compute(K key, 1560 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 1561 throw new UnsupportedOperationException(); 1562 } 1563 1564 @Override 1565 public V merge(K key, V value, 1566 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 1567 throw new UnsupportedOperationException(); 1568 } 1569 1570 /** 1571 * We need this class in addition to UnmodifiableSet as 1572 * Map.Entries themselves permit modification of the backing Map 1573 * via their setValue operation. This class is subtle: there are 1574 * many possible attacks that must be thwarted. 1575 * 1576 * @serial include 1577 */ 1578 static class UnmodifiableEntrySet<K,V> 1579 extends UnmodifiableSet<Map.Entry<K,V>> { 1580 private static final long serialVersionUID = 7854390611657943733L; 1581 1582 @SuppressWarnings({"unchecked", "rawtypes"}) 1583 UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) { 1584 // Need to cast to raw in order to work around a limitation in the type system 1585 super((Set)s); 1586 } 1587 1588 static <K, V> Consumer<Map.Entry<K, V>> entryConsumer(Consumer<? super Entry<K, V>> action) { 1589 return e -> action.accept(new UnmodifiableEntry<>(e)); 1590 } 1591 1592 public void forEach(Consumer<? super Entry<K, V>> action) { 1593 Objects.requireNonNull(action); 1594 c.forEach(entryConsumer(action)); 1595 } 1596 1597 static final class UnmodifiableEntrySetSpliterator<K, V> 1598 implements Spliterator<Entry<K,V>> { 1599 final Spliterator<Map.Entry<K, V>> s; 1600 1601 UnmodifiableEntrySetSpliterator(Spliterator<Entry<K, V>> s) { 1602 this.s = s; 1603 } 1604 1605 @Override 1606 public boolean tryAdvance(Consumer<? super Entry<K, V>> action) { 1607 Objects.requireNonNull(action); 1608 return s.tryAdvance(entryConsumer(action)); 1609 } 1610 1611 @Override 1612 public void forEachRemaining(Consumer<? super Entry<K, V>> action) { 1613 Objects.requireNonNull(action); 1614 s.forEachRemaining(entryConsumer(action)); 1615 } 1616 1617 @Override 1618 public Spliterator<Entry<K, V>> trySplit() { 1619 Spliterator<Entry<K, V>> split = s.trySplit(); 1620 return split == null 1621 ? null 1622 : new UnmodifiableEntrySetSpliterator<>(split); 1623 } 1624 1625 @Override 1626 public long estimateSize() { 1627 return s.estimateSize(); 1628 } 1629 1630 @Override 1631 public long getExactSizeIfKnown() { 1632 return s.getExactSizeIfKnown(); 1633 } 1634 1635 @Override 1636 public int characteristics() { 1637 return s.characteristics(); 1638 } 1639 1640 @Override 1641 public boolean hasCharacteristics(int characteristics) { 1642 return s.hasCharacteristics(characteristics); 1643 } 1644 1645 @Override 1646 public Comparator<? super Entry<K, V>> getComparator() { 1647 return s.getComparator(); 1648 } 1649 } 1650 1651 @SuppressWarnings("unchecked") 1652 public Spliterator<Entry<K,V>> spliterator() { 1653 return new UnmodifiableEntrySetSpliterator<>( 1654 (Spliterator<Map.Entry<K, V>>) c.spliterator()); 1655 } 1656 1657 @Override 1658 public Stream<Entry<K,V>> stream() { 1659 return StreamSupport.stream(spliterator(), false); 1660 } 1661 1662 @Override 1663 public Stream<Entry<K,V>> parallelStream() { 1664 return StreamSupport.stream(spliterator(), true); 1665 } 1666 1667 public Iterator<Map.Entry<K,V>> iterator() { 1668 return new Iterator<Map.Entry<K,V>>() { 1669 private final Iterator<? extends Map.Entry<? extends K, ? extends V>> i = c.iterator(); 1670 1671 public boolean hasNext() { 1672 return i.hasNext(); 1673 } 1674 public Map.Entry<K,V> next() { 1675 return new UnmodifiableEntry<>(i.next()); 1676 } 1677 public void remove() { 1678 throw new UnsupportedOperationException(); 1679 } 1680 // Android-note: This seems pretty inconsistent. Unlike other subclasses, we aren't 1681 // delegating to the subclass iterator here. Seems like an oversight. 1682 }; 1683 } 1684 1685 @SuppressWarnings("unchecked") 1686 public Object[] toArray() { 1687 Object[] a = c.toArray(); 1688 for (int i=0; i<a.length; i++) 1689 a[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)a[i]); 1690 return a; 1691 } 1692 1693 @SuppressWarnings("unchecked") 1694 public <T> T[] toArray(T[] a) { 1695 // We don't pass a to c.toArray, to avoid window of 1696 // vulnerability wherein an unscrupulous multithreaded client 1697 // could get his hands on raw (unwrapped) Entries from c. 1698 Object[] arr = c.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); 1699 1700 for (int i=0; i<arr.length; i++) 1701 arr[i] = new UnmodifiableEntry<>((Map.Entry<? extends K, ? extends V>)arr[i]); 1702 1703 if (arr.length > a.length) 1704 return (T[])arr; 1705 1706 System.arraycopy(arr, 0, a, 0, arr.length); 1707 if (a.length > arr.length) 1708 a[arr.length] = null; 1709 return a; 1710 } 1711 1712 /** 1713 * This method is overridden to protect the backing set against 1714 * an object with a nefarious equals function that senses 1715 * that the equality-candidate is Map.Entry and calls its 1716 * setValue method. 1717 */ 1718 public boolean contains(Object o) { 1719 if (!(o instanceof Map.Entry)) 1720 return false; 1721 return c.contains( 1722 new UnmodifiableEntry<>((Map.Entry<?,?>) o)); 1723 } 1724 1725 /** 1726 * The next two methods are overridden to protect against 1727 * an unscrupulous List whose contains(Object o) method senses 1728 * when o is a Map.Entry, and calls o.setValue. 1729 */ 1730 public boolean containsAll(Collection<?> coll) { 1731 for (Object e : coll) { 1732 if (!contains(e)) // Invokes safe contains() above 1733 return false; 1734 } 1735 return true; 1736 } 1737 public boolean equals(Object o) { 1738 if (o == this) 1739 return true; 1740 1741 if (!(o instanceof Set)) 1742 return false; 1743 Set<?> s = (Set<?>) o; 1744 if (s.size() != c.size()) 1745 return false; 1746 return containsAll(s); // Invokes safe containsAll() above 1747 } 1748 1749 /** 1750 * This "wrapper class" serves two purposes: it prevents 1751 * the client from modifying the backing Map, by short-circuiting 1752 * the setValue method, and it protects the backing Map against 1753 * an ill-behaved Map.Entry that attempts to modify another 1754 * Map Entry when asked to perform an equality check. 1755 */ 1756 private static class UnmodifiableEntry<K,V> implements Map.Entry<K,V> { 1757 private Map.Entry<? extends K, ? extends V> e; 1758 1759 UnmodifiableEntry(Map.Entry<? extends K, ? extends V> e) 1760 {this.e = Objects.requireNonNull(e);} 1761 1762 public K getKey() {return e.getKey();} 1763 public V getValue() {return e.getValue();} 1764 public V setValue(V value) { 1765 throw new UnsupportedOperationException(); 1766 } 1767 public int hashCode() {return e.hashCode();} 1768 public boolean equals(Object o) { 1769 if (this == o) 1770 return true; 1771 if (!(o instanceof Map.Entry)) 1772 return false; 1773 Map.Entry<?,?> t = (Map.Entry<?,?>)o; 1774 return eq(e.getKey(), t.getKey()) && 1775 eq(e.getValue(), t.getValue()); 1776 } 1777 public String toString() {return e.toString();} 1778 } 1779 } 1780 } 1781 1782 /** 1783 * Returns an unmodifiable view of the specified sorted map. This method 1784 * allows modules to provide users with "read-only" access to internal 1785 * sorted maps. Query operations on the returned sorted map "read through" 1786 * to the specified sorted map. Attempts to modify the returned 1787 * sorted map, whether direct, via its collection views, or via its 1788 * <tt>subMap</tt>, <tt>headMap</tt>, or <tt>tailMap</tt> views, result in 1789 * an <tt>UnsupportedOperationException</tt>.<p> 1790 * 1791 * The returned sorted map will be serializable if the specified sorted map 1792 * is serializable. 1793 * 1794 * @param <K> the class of the map keys 1795 * @param <V> the class of the map values 1796 * @param m the sorted map for which an unmodifiable view is to be 1797 * returned. 1798 * @return an unmodifiable view of the specified sorted map. 1799 */ 1800 public static <K,V> SortedMap<K,V> unmodifiableSortedMap(SortedMap<K, ? extends V> m) { 1801 return new UnmodifiableSortedMap<>(m); 1802 } 1803 1804 /** 1805 * @serial include 1806 */ 1807 static class UnmodifiableSortedMap<K,V> 1808 extends UnmodifiableMap<K,V> 1809 implements SortedMap<K,V>, Serializable { 1810 private static final long serialVersionUID = -8806743815996713206L; 1811 1812 private final SortedMap<K, ? extends V> sm; 1813 1814 UnmodifiableSortedMap(SortedMap<K, ? extends V> m) {super(m); sm = m; } 1815 public Comparator<? super K> comparator() { return sm.comparator(); } 1816 public SortedMap<K,V> subMap(K fromKey, K toKey) 1817 { return new UnmodifiableSortedMap<>(sm.subMap(fromKey, toKey)); } 1818 public SortedMap<K,V> headMap(K toKey) 1819 { return new UnmodifiableSortedMap<>(sm.headMap(toKey)); } 1820 public SortedMap<K,V> tailMap(K fromKey) 1821 { return new UnmodifiableSortedMap<>(sm.tailMap(fromKey)); } 1822 public K firstKey() { return sm.firstKey(); } 1823 public K lastKey() { return sm.lastKey(); } 1824 } 1825 1826 /** 1827 * Returns an unmodifiable view of the specified navigable map. This method 1828 * allows modules to provide users with "read-only" access to internal 1829 * navigable maps. Query operations on the returned navigable map "read 1830 * through" to the specified navigable map. Attempts to modify the returned 1831 * navigable map, whether direct, via its collection views, or via its 1832 * {@code subMap}, {@code headMap}, or {@code tailMap} views, result in 1833 * an {@code UnsupportedOperationException}.<p> 1834 * 1835 * The returned navigable map will be serializable if the specified 1836 * navigable map is serializable. 1837 * 1838 * @param <K> the class of the map keys 1839 * @param <V> the class of the map values 1840 * @param m the navigable map for which an unmodifiable view is to be 1841 * returned 1842 * @return an unmodifiable view of the specified navigable map 1843 * @since 1.8 1844 * @hide 1845 */ 1846 public static <K,V> NavigableMap<K,V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> m) { 1847 return new UnmodifiableNavigableMap<>(m); 1848 } 1849 1850 /** 1851 * @serial include 1852 */ 1853 static class UnmodifiableNavigableMap<K,V> 1854 extends UnmodifiableSortedMap<K,V> 1855 implements NavigableMap<K,V>, Serializable { 1856 private static final long serialVersionUID = -4858195264774772197L; 1857 1858 /** 1859 * A class for the {@link EMPTY_NAVIGABLE_MAP} which needs readResolve 1860 * to preserve singleton property. 1861 * 1862 * @param <K> type of keys, if there were any, and of bounds 1863 * @param <V> type of values, if there were any 1864 */ 1865 private static class EmptyNavigableMap<K,V> extends UnmodifiableNavigableMap<K,V> 1866 implements Serializable { 1867 1868 private static final long serialVersionUID = -2239321462712562324L; 1869 1870 EmptyNavigableMap() { super(new TreeMap<K,V>()); } 1871 1872 @Override 1873 public NavigableSet<K> navigableKeySet() 1874 { return emptyNavigableSet(); } 1875 1876 private Object readResolve() { return EMPTY_NAVIGABLE_MAP; } 1877 } 1878 1879 /** 1880 * Singleton for {@link emptyNavigableMap()} which is also immutable. 1881 */ 1882 private static final EmptyNavigableMap<?,?> EMPTY_NAVIGABLE_MAP = 1883 new EmptyNavigableMap<>(); 1884 1885 /** 1886 * The instance we wrap and protect. 1887 */ 1888 private final NavigableMap<K, ? extends V> nm; 1889 1890 UnmodifiableNavigableMap(NavigableMap<K, ? extends V> m) 1891 {super(m); nm = m;} 1892 1893 public K lowerKey(K key) { return nm.lowerKey(key); } 1894 public K floorKey(K key) { return nm.floorKey(key); } 1895 public K ceilingKey(K key) { return nm.ceilingKey(key); } 1896 public K higherKey(K key) { return nm.higherKey(key); } 1897 1898 @SuppressWarnings("unchecked") 1899 public Entry<K, V> lowerEntry(K key) { 1900 Entry<K,V> lower = (Entry<K, V>) nm.lowerEntry(key); 1901 return (null != lower) 1902 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(lower) 1903 : null; 1904 } 1905 1906 @SuppressWarnings("unchecked") 1907 public Entry<K, V> floorEntry(K key) { 1908 Entry<K,V> floor = (Entry<K, V>) nm.floorEntry(key); 1909 return (null != floor) 1910 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(floor) 1911 : null; 1912 } 1913 1914 @SuppressWarnings("unchecked") 1915 public Entry<K, V> ceilingEntry(K key) { 1916 Entry<K,V> ceiling = (Entry<K, V>) nm.ceilingEntry(key); 1917 return (null != ceiling) 1918 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(ceiling) 1919 : null; 1920 } 1921 1922 1923 @SuppressWarnings("unchecked") 1924 public Entry<K, V> higherEntry(K key) { 1925 Entry<K,V> higher = (Entry<K, V>) nm.higherEntry(key); 1926 return (null != higher) 1927 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(higher) 1928 : null; 1929 } 1930 1931 @SuppressWarnings("unchecked") 1932 public Entry<K, V> firstEntry() { 1933 Entry<K,V> first = (Entry<K, V>) nm.firstEntry(); 1934 return (null != first) 1935 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(first) 1936 : null; 1937 } 1938 1939 @SuppressWarnings("unchecked") 1940 public Entry<K, V> lastEntry() { 1941 Entry<K,V> last = (Entry<K, V>) nm.lastEntry(); 1942 return (null != last) 1943 ? new UnmodifiableEntrySet.UnmodifiableEntry<>(last) 1944 : null; 1945 } 1946 1947 public Entry<K, V> pollFirstEntry() 1948 { throw new UnsupportedOperationException(); } 1949 public Entry<K, V> pollLastEntry() 1950 { throw new UnsupportedOperationException(); } 1951 public NavigableMap<K, V> descendingMap() 1952 { return unmodifiableNavigableMap(nm.descendingMap()); } 1953 public NavigableSet<K> navigableKeySet() 1954 { return unmodifiableNavigableSet(nm.navigableKeySet()); } 1955 public NavigableSet<K> descendingKeySet() 1956 { return unmodifiableNavigableSet(nm.descendingKeySet()); } 1957 1958 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 1959 return unmodifiableNavigableMap( 1960 nm.subMap(fromKey, fromInclusive, toKey, toInclusive)); 1961 } 1962 1963 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) 1964 { return unmodifiableNavigableMap(nm.headMap(toKey, inclusive)); } 1965 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) 1966 { return unmodifiableNavigableMap(nm.tailMap(fromKey, inclusive)); } 1967 } 1968 1969 // Synch Wrappers 1970 1971 /** 1972 * Returns a synchronized (thread-safe) collection backed by the specified 1973 * collection. In order to guarantee serial access, it is critical that 1974 * <strong>all</strong> access to the backing collection is accomplished 1975 * through the returned collection.<p> 1976 * 1977 * It is imperative that the user manually synchronize on the returned 1978 * collection when traversing it via {@link Iterator}, {@link Spliterator} 1979 * or {@link Stream}: 1980 * <pre> 1981 * Collection c = Collections.synchronizedCollection(myCollection); 1982 * ... 1983 * synchronized (c) { 1984 * Iterator i = c.iterator(); // Must be in the synchronized block 1985 * while (i.hasNext()) 1986 * foo(i.next()); 1987 * } 1988 * </pre> 1989 * Failure to follow this advice may result in non-deterministic behavior. 1990 * 1991 * <p>The returned collection does <i>not</i> pass the {@code hashCode} 1992 * and {@code equals} operations through to the backing collection, but 1993 * relies on {@code Object}'s equals and hashCode methods. This is 1994 * necessary to preserve the contracts of these operations in the case 1995 * that the backing collection is a set or a list.<p> 1996 * 1997 * The returned collection will be serializable if the specified collection 1998 * is serializable. 1999 * 2000 * @param <T> the class of the objects in the collection 2001 * @param c the collection to be "wrapped" in a synchronized collection. 2002 * @return a synchronized view of the specified collection. 2003 */ 2004 public static <T> Collection<T> synchronizedCollection(Collection<T> c) { 2005 return new SynchronizedCollection<>(c); 2006 } 2007 2008 static <T> Collection<T> synchronizedCollection(Collection<T> c, Object mutex) { 2009 return new SynchronizedCollection<>(c, mutex); 2010 } 2011 2012 /** 2013 * @serial include 2014 */ 2015 static class SynchronizedCollection<E> implements Collection<E>, Serializable { 2016 private static final long serialVersionUID = 3053995032091335093L; 2017 2018 final Collection<E> c; // Backing Collection 2019 final Object mutex; // Object on which to synchronize 2020 2021 SynchronizedCollection(Collection<E> c) { 2022 this.c = Objects.requireNonNull(c); 2023 mutex = this; 2024 } 2025 2026 SynchronizedCollection(Collection<E> c, Object mutex) { 2027 this.c = Objects.requireNonNull(c); 2028 this.mutex = Objects.requireNonNull(mutex); 2029 } 2030 2031 public int size() { 2032 synchronized (mutex) {return c.size();} 2033 } 2034 public boolean isEmpty() { 2035 synchronized (mutex) {return c.isEmpty();} 2036 } 2037 public boolean contains(Object o) { 2038 synchronized (mutex) {return c.contains(o);} 2039 } 2040 public Object[] toArray() { 2041 synchronized (mutex) {return c.toArray();} 2042 } 2043 public <T> T[] toArray(T[] a) { 2044 synchronized (mutex) {return c.toArray(a);} 2045 } 2046 2047 public Iterator<E> iterator() { 2048 return c.iterator(); // Must be manually synched by user! 2049 } 2050 2051 public boolean add(E e) { 2052 synchronized (mutex) {return c.add(e);} 2053 } 2054 public boolean remove(Object o) { 2055 synchronized (mutex) {return c.remove(o);} 2056 } 2057 2058 public boolean containsAll(Collection<?> coll) { 2059 synchronized (mutex) {return c.containsAll(coll);} 2060 } 2061 public boolean addAll(Collection<? extends E> coll) { 2062 synchronized (mutex) {return c.addAll(coll);} 2063 } 2064 public boolean removeAll(Collection<?> coll) { 2065 synchronized (mutex) {return c.removeAll(coll);} 2066 } 2067 public boolean retainAll(Collection<?> coll) { 2068 synchronized (mutex) {return c.retainAll(coll);} 2069 } 2070 public void clear() { 2071 synchronized (mutex) {c.clear();} 2072 } 2073 public String toString() { 2074 synchronized (mutex) {return c.toString();} 2075 } 2076 // Override default methods in Collection 2077 @Override 2078 public void forEach(Consumer<? super E> consumer) { 2079 synchronized (mutex) {c.forEach(consumer);} 2080 } 2081 @Override 2082 public boolean removeIf(Predicate<? super E> filter) { 2083 synchronized (mutex) {return c.removeIf(filter);} 2084 } 2085 @Override 2086 public Spliterator<E> spliterator() { 2087 return c.spliterator(); // Must be manually synched by user! 2088 } 2089 @Override 2090 public Stream<E> stream() { 2091 return c.stream(); // Must be manually synched by user! 2092 } 2093 @Override 2094 public Stream<E> parallelStream() { 2095 return c.parallelStream(); // Must be manually synched by user! 2096 } 2097 private void writeObject(ObjectOutputStream s) throws IOException { 2098 synchronized (mutex) {s.defaultWriteObject();} 2099 } 2100 } 2101 2102 /** 2103 * Returns a synchronized (thread-safe) set backed by the specified 2104 * set. In order to guarantee serial access, it is critical that 2105 * <strong>all</strong> access to the backing set is accomplished 2106 * through the returned set.<p> 2107 * 2108 * It is imperative that the user manually synchronize on the returned 2109 * set when iterating over it: 2110 * <pre> 2111 * Set s = Collections.synchronizedSet(new HashSet()); 2112 * ... 2113 * synchronized (s) { 2114 * Iterator i = s.iterator(); // Must be in the synchronized block 2115 * while (i.hasNext()) 2116 * foo(i.next()); 2117 * } 2118 * </pre> 2119 * Failure to follow this advice may result in non-deterministic behavior. 2120 * 2121 * <p>The returned set will be serializable if the specified set is 2122 * serializable. 2123 * 2124 * @param <T> the class of the objects in the set 2125 * @param s the set to be "wrapped" in a synchronized set. 2126 * @return a synchronized view of the specified set. 2127 */ 2128 public static <T> Set<T> synchronizedSet(Set<T> s) { 2129 return new SynchronizedSet<>(s); 2130 } 2131 2132 static <T> Set<T> synchronizedSet(Set<T> s, Object mutex) { 2133 return new SynchronizedSet<>(s, mutex); 2134 } 2135 2136 /** 2137 * @serial include 2138 */ 2139 static class SynchronizedSet<E> 2140 extends SynchronizedCollection<E> 2141 implements Set<E> { 2142 private static final long serialVersionUID = 487447009682186044L; 2143 2144 SynchronizedSet(Set<E> s) { 2145 super(s); 2146 } 2147 SynchronizedSet(Set<E> s, Object mutex) { 2148 super(s, mutex); 2149 } 2150 2151 public boolean equals(Object o) { 2152 if (this == o) 2153 return true; 2154 synchronized (mutex) {return c.equals(o);} 2155 } 2156 public int hashCode() { 2157 synchronized (mutex) {return c.hashCode();} 2158 } 2159 } 2160 2161 /** 2162 * Returns a synchronized (thread-safe) sorted set backed by the specified 2163 * sorted set. In order to guarantee serial access, it is critical that 2164 * <strong>all</strong> access to the backing sorted set is accomplished 2165 * through the returned sorted set (or its views).<p> 2166 * 2167 * It is imperative that the user manually synchronize on the returned 2168 * sorted set when iterating over it or any of its <tt>subSet</tt>, 2169 * <tt>headSet</tt>, or <tt>tailSet</tt> views. 2170 * <pre> 2171 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); 2172 * ... 2173 * synchronized (s) { 2174 * Iterator i = s.iterator(); // Must be in the synchronized block 2175 * while (i.hasNext()) 2176 * foo(i.next()); 2177 * } 2178 * </pre> 2179 * or: 2180 * <pre> 2181 * SortedSet s = Collections.synchronizedSortedSet(new TreeSet()); 2182 * SortedSet s2 = s.headSet(foo); 2183 * ... 2184 * synchronized (s) { // Note: s, not s2!!! 2185 * Iterator i = s2.iterator(); // Must be in the synchronized block 2186 * while (i.hasNext()) 2187 * foo(i.next()); 2188 * } 2189 * </pre> 2190 * Failure to follow this advice may result in non-deterministic behavior. 2191 * 2192 * <p>The returned sorted set will be serializable if the specified 2193 * sorted set is serializable. 2194 * 2195 * @param <T> the class of the objects in the set 2196 * @param s the sorted set to be "wrapped" in a synchronized sorted set. 2197 * @return a synchronized view of the specified sorted set. 2198 */ 2199 public static <T> SortedSet<T> synchronizedSortedSet(SortedSet<T> s) { 2200 return new SynchronizedSortedSet<>(s); 2201 } 2202 2203 /** 2204 * @serial include 2205 */ 2206 static class SynchronizedSortedSet<E> 2207 extends SynchronizedSet<E> 2208 implements SortedSet<E> 2209 { 2210 private static final long serialVersionUID = 8695801310862127406L; 2211 2212 private final SortedSet<E> ss; 2213 2214 SynchronizedSortedSet(SortedSet<E> s) { 2215 super(s); 2216 ss = s; 2217 } 2218 SynchronizedSortedSet(SortedSet<E> s, Object mutex) { 2219 super(s, mutex); 2220 ss = s; 2221 } 2222 2223 public Comparator<? super E> comparator() { 2224 synchronized (mutex) {return ss.comparator();} 2225 } 2226 2227 public SortedSet<E> subSet(E fromElement, E toElement) { 2228 synchronized (mutex) { 2229 return new SynchronizedSortedSet<>( 2230 ss.subSet(fromElement, toElement), mutex); 2231 } 2232 } 2233 public SortedSet<E> headSet(E toElement) { 2234 synchronized (mutex) { 2235 return new SynchronizedSortedSet<>(ss.headSet(toElement), mutex); 2236 } 2237 } 2238 public SortedSet<E> tailSet(E fromElement) { 2239 synchronized (mutex) { 2240 return new SynchronizedSortedSet<>(ss.tailSet(fromElement),mutex); 2241 } 2242 } 2243 2244 public E first() { 2245 synchronized (mutex) {return ss.first();} 2246 } 2247 public E last() { 2248 synchronized (mutex) {return ss.last();} 2249 } 2250 } 2251 2252 /** 2253 * Returns a synchronized (thread-safe) navigable set backed by the 2254 * specified navigable set. In order to guarantee serial access, it is 2255 * critical that <strong>all</strong> access to the backing navigable set is 2256 * accomplished through the returned navigable set (or its views).<p> 2257 * 2258 * It is imperative that the user manually synchronize on the returned 2259 * navigable set when iterating over it or any of its {@code subSet}, 2260 * {@code headSet}, or {@code tailSet} views. 2261 * <pre> 2262 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet()); 2263 * ... 2264 * synchronized (s) { 2265 * Iterator i = s.iterator(); // Must be in the synchronized block 2266 * while (i.hasNext()) 2267 * foo(i.next()); 2268 * } 2269 * </pre> 2270 * or: 2271 * <pre> 2272 * NavigableSet s = Collections.synchronizedNavigableSet(new TreeSet()); 2273 * NavigableSet s2 = s.headSet(foo, true); 2274 * ... 2275 * synchronized (s) { // Note: s, not s2!!! 2276 * Iterator i = s2.iterator(); // Must be in the synchronized block 2277 * while (i.hasNext()) 2278 * foo(i.next()); 2279 * } 2280 * </pre> 2281 * Failure to follow this advice may result in non-deterministic behavior. 2282 * 2283 * <p>The returned navigable set will be serializable if the specified 2284 * navigable set is serializable. 2285 * 2286 * @param <T> the class of the objects in the set 2287 * @param s the navigable set to be "wrapped" in a synchronized navigable 2288 * set 2289 * @return a synchronized view of the specified navigable set 2290 * @since 1.8 2291 * @hide 2292 */ 2293 public static <T> NavigableSet<T> synchronizedNavigableSet(NavigableSet<T> s) { 2294 return new SynchronizedNavigableSet<>(s); 2295 } 2296 2297 /** 2298 * @serial include 2299 */ 2300 static class SynchronizedNavigableSet<E> 2301 extends SynchronizedSortedSet<E> 2302 implements NavigableSet<E> 2303 { 2304 private static final long serialVersionUID = -5505529816273629798L; 2305 2306 private final NavigableSet<E> ns; 2307 2308 SynchronizedNavigableSet(NavigableSet<E> s) { 2309 super(s); 2310 ns = s; 2311 } 2312 2313 SynchronizedNavigableSet(NavigableSet<E> s, Object mutex) { 2314 super(s, mutex); 2315 ns = s; 2316 } 2317 public E lower(E e) { synchronized (mutex) {return ns.lower(e);} } 2318 public E floor(E e) { synchronized (mutex) {return ns.floor(e);} } 2319 public E ceiling(E e) { synchronized (mutex) {return ns.ceiling(e);} } 2320 public E higher(E e) { synchronized (mutex) {return ns.higher(e);} } 2321 public E pollFirst() { synchronized (mutex) {return ns.pollFirst();} } 2322 public E pollLast() { synchronized (mutex) {return ns.pollLast();} } 2323 2324 public NavigableSet<E> descendingSet() { 2325 synchronized (mutex) { 2326 return new SynchronizedNavigableSet<>(ns.descendingSet(), mutex); 2327 } 2328 } 2329 2330 public Iterator<E> descendingIterator() 2331 { synchronized (mutex) { return descendingSet().iterator(); } } 2332 2333 public NavigableSet<E> subSet(E fromElement, E toElement) { 2334 synchronized (mutex) { 2335 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, true, toElement, false), mutex); 2336 } 2337 } 2338 public NavigableSet<E> headSet(E toElement) { 2339 synchronized (mutex) { 2340 return new SynchronizedNavigableSet<>(ns.headSet(toElement, false), mutex); 2341 } 2342 } 2343 public NavigableSet<E> tailSet(E fromElement) { 2344 synchronized (mutex) { 2345 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, true), mutex); 2346 } 2347 } 2348 2349 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 2350 synchronized (mutex) { 2351 return new SynchronizedNavigableSet<>(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), mutex); 2352 } 2353 } 2354 2355 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 2356 synchronized (mutex) { 2357 return new SynchronizedNavigableSet<>(ns.headSet(toElement, inclusive), mutex); 2358 } 2359 } 2360 2361 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 2362 synchronized (mutex) { 2363 return new SynchronizedNavigableSet<>(ns.tailSet(fromElement, inclusive), mutex); 2364 } 2365 } 2366 } 2367 2368 /** 2369 * Returns a synchronized (thread-safe) list backed by the specified 2370 * list. In order to guarantee serial access, it is critical that 2371 * <strong>all</strong> access to the backing list is accomplished 2372 * through the returned list.<p> 2373 * 2374 * It is imperative that the user manually synchronize on the returned 2375 * list when iterating over it: 2376 * <pre> 2377 * List list = Collections.synchronizedList(new ArrayList()); 2378 * ... 2379 * synchronized (list) { 2380 * Iterator i = list.iterator(); // Must be in synchronized block 2381 * while (i.hasNext()) 2382 * foo(i.next()); 2383 * } 2384 * </pre> 2385 * Failure to follow this advice may result in non-deterministic behavior. 2386 * 2387 * <p>The returned list will be serializable if the specified list is 2388 * serializable. 2389 * 2390 * @param <T> the class of the objects in the list 2391 * @param list the list to be "wrapped" in a synchronized list. 2392 * @return a synchronized view of the specified list. 2393 */ 2394 public static <T> List<T> synchronizedList(List<T> list) { 2395 return (list instanceof RandomAccess ? 2396 new SynchronizedRandomAccessList<>(list) : 2397 new SynchronizedList<>(list)); 2398 } 2399 2400 static <T> List<T> synchronizedList(List<T> list, Object mutex) { 2401 return (list instanceof RandomAccess ? 2402 new SynchronizedRandomAccessList<>(list, mutex) : 2403 new SynchronizedList<>(list, mutex)); 2404 } 2405 2406 /** 2407 * @serial include 2408 */ 2409 static class SynchronizedList<E> 2410 extends SynchronizedCollection<E> 2411 implements List<E> { 2412 private static final long serialVersionUID = -7754090372962971524L; 2413 2414 final List<E> list; 2415 2416 SynchronizedList(List<E> list) { 2417 super(list); 2418 this.list = list; 2419 } 2420 SynchronizedList(List<E> list, Object mutex) { 2421 super(list, mutex); 2422 this.list = list; 2423 } 2424 2425 public boolean equals(Object o) { 2426 if (this == o) 2427 return true; 2428 synchronized (mutex) {return list.equals(o);} 2429 } 2430 public int hashCode() { 2431 synchronized (mutex) {return list.hashCode();} 2432 } 2433 2434 public E get(int index) { 2435 synchronized (mutex) {return list.get(index);} 2436 } 2437 public E set(int index, E element) { 2438 synchronized (mutex) {return list.set(index, element);} 2439 } 2440 public void add(int index, E element) { 2441 synchronized (mutex) {list.add(index, element);} 2442 } 2443 public E remove(int index) { 2444 synchronized (mutex) {return list.remove(index);} 2445 } 2446 2447 public int indexOf(Object o) { 2448 synchronized (mutex) {return list.indexOf(o);} 2449 } 2450 public int lastIndexOf(Object o) { 2451 synchronized (mutex) {return list.lastIndexOf(o);} 2452 } 2453 2454 public boolean addAll(int index, Collection<? extends E> c) { 2455 synchronized (mutex) {return list.addAll(index, c);} 2456 } 2457 2458 public ListIterator<E> listIterator() { 2459 return list.listIterator(); // Must be manually synched by user 2460 } 2461 2462 public ListIterator<E> listIterator(int index) { 2463 return list.listIterator(index); // Must be manually synched by user 2464 } 2465 2466 public List<E> subList(int fromIndex, int toIndex) { 2467 synchronized (mutex) { 2468 return new SynchronizedList<>(list.subList(fromIndex, toIndex), 2469 mutex); 2470 } 2471 } 2472 2473 @Override 2474 public void replaceAll(UnaryOperator<E> operator) { 2475 synchronized (mutex) {list.replaceAll(operator);} 2476 } 2477 @Override 2478 public void sort(Comparator<? super E> c) { 2479 synchronized (mutex) {list.sort(c);} 2480 } 2481 2482 /** 2483 * SynchronizedRandomAccessList instances are serialized as 2484 * SynchronizedList instances to allow them to be deserialized 2485 * in pre-1.4 JREs (which do not have SynchronizedRandomAccessList). 2486 * This method inverts the transformation. As a beneficial 2487 * side-effect, it also grafts the RandomAccess marker onto 2488 * SynchronizedList instances that were serialized in pre-1.4 JREs. 2489 * 2490 * Note: Unfortunately, SynchronizedRandomAccessList instances 2491 * serialized in 1.4.1 and deserialized in 1.4 will become 2492 * SynchronizedList instances, as this method was missing in 1.4. 2493 */ 2494 private Object readResolve() { 2495 return (list instanceof RandomAccess 2496 ? new SynchronizedRandomAccessList<>(list) 2497 : this); 2498 } 2499 } 2500 2501 /** 2502 * @serial include 2503 */ 2504 static class SynchronizedRandomAccessList<E> 2505 extends SynchronizedList<E> 2506 implements RandomAccess { 2507 2508 SynchronizedRandomAccessList(List<E> list) { 2509 super(list); 2510 } 2511 2512 SynchronizedRandomAccessList(List<E> list, Object mutex) { 2513 super(list, mutex); 2514 } 2515 2516 public List<E> subList(int fromIndex, int toIndex) { 2517 synchronized (mutex) { 2518 return new SynchronizedRandomAccessList<>( 2519 list.subList(fromIndex, toIndex), mutex); 2520 } 2521 } 2522 2523 private static final long serialVersionUID = 1530674583602358482L; 2524 2525 /** 2526 * Allows instances to be deserialized in pre-1.4 JREs (which do 2527 * not have SynchronizedRandomAccessList). SynchronizedList has 2528 * a readResolve method that inverts this transformation upon 2529 * deserialization. 2530 */ 2531 private Object writeReplace() { 2532 return new SynchronizedList<>(list); 2533 } 2534 } 2535 2536 /** 2537 * Returns a synchronized (thread-safe) map backed by the specified 2538 * map. In order to guarantee serial access, it is critical that 2539 * <strong>all</strong> access to the backing map is accomplished 2540 * through the returned map.<p> 2541 * 2542 * It is imperative that the user manually synchronize on the returned 2543 * map when iterating over any of its collection views: 2544 * <pre> 2545 * Map m = Collections.synchronizedMap(new HashMap()); 2546 * ... 2547 * Set s = m.keySet(); // Needn't be in synchronized block 2548 * ... 2549 * synchronized (m) { // Synchronizing on m, not s! 2550 * Iterator i = s.iterator(); // Must be in synchronized block 2551 * while (i.hasNext()) 2552 * foo(i.next()); 2553 * } 2554 * </pre> 2555 * Failure to follow this advice may result in non-deterministic behavior. 2556 * 2557 * <p>The returned map will be serializable if the specified map is 2558 * serializable. 2559 * 2560 * @param <K> the class of the map keys 2561 * @param <V> the class of the map values 2562 * @param m the map to be "wrapped" in a synchronized map. 2563 * @return a synchronized view of the specified map. 2564 */ 2565 public static <K,V> Map<K,V> synchronizedMap(Map<K,V> m) { 2566 return new SynchronizedMap<>(m); 2567 } 2568 2569 /** 2570 * @serial include 2571 */ 2572 private static class SynchronizedMap<K,V> 2573 implements Map<K,V>, Serializable { 2574 private static final long serialVersionUID = 1978198479659022715L; 2575 2576 private final Map<K,V> m; // Backing Map 2577 final Object mutex; // Object on which to synchronize 2578 2579 SynchronizedMap(Map<K,V> m) { 2580 this.m = Objects.requireNonNull(m); 2581 mutex = this; 2582 } 2583 2584 SynchronizedMap(Map<K,V> m, Object mutex) { 2585 this.m = m; 2586 this.mutex = mutex; 2587 } 2588 2589 public int size() { 2590 synchronized (mutex) {return m.size();} 2591 } 2592 public boolean isEmpty() { 2593 synchronized (mutex) {return m.isEmpty();} 2594 } 2595 public boolean containsKey(Object key) { 2596 synchronized (mutex) {return m.containsKey(key);} 2597 } 2598 public boolean containsValue(Object value) { 2599 synchronized (mutex) {return m.containsValue(value);} 2600 } 2601 public V get(Object key) { 2602 synchronized (mutex) {return m.get(key);} 2603 } 2604 2605 public V put(K key, V value) { 2606 synchronized (mutex) {return m.put(key, value);} 2607 } 2608 public V remove(Object key) { 2609 synchronized (mutex) {return m.remove(key);} 2610 } 2611 public void putAll(Map<? extends K, ? extends V> map) { 2612 synchronized (mutex) {m.putAll(map);} 2613 } 2614 public void clear() { 2615 synchronized (mutex) {m.clear();} 2616 } 2617 2618 private transient Set<K> keySet; 2619 private transient Set<Map.Entry<K,V>> entrySet; 2620 private transient Collection<V> values; 2621 2622 public Set<K> keySet() { 2623 synchronized (mutex) { 2624 if (keySet==null) 2625 keySet = new SynchronizedSet<>(m.keySet(), mutex); 2626 return keySet; 2627 } 2628 } 2629 2630 public Set<Map.Entry<K,V>> entrySet() { 2631 synchronized (mutex) { 2632 if (entrySet==null) 2633 entrySet = new SynchronizedSet<>(m.entrySet(), mutex); 2634 return entrySet; 2635 } 2636 } 2637 2638 public Collection<V> values() { 2639 synchronized (mutex) { 2640 if (values==null) 2641 values = new SynchronizedCollection<>(m.values(), mutex); 2642 return values; 2643 } 2644 } 2645 2646 public boolean equals(Object o) { 2647 if (this == o) 2648 return true; 2649 synchronized (mutex) {return m.equals(o);} 2650 } 2651 public int hashCode() { 2652 synchronized (mutex) {return m.hashCode();} 2653 } 2654 public String toString() { 2655 synchronized (mutex) {return m.toString();} 2656 } 2657 2658 // Override default methods in Map 2659 @Override 2660 public V getOrDefault(Object k, V defaultValue) { 2661 synchronized (mutex) {return m.getOrDefault(k, defaultValue);} 2662 } 2663 @Override 2664 public void forEach(BiConsumer<? super K, ? super V> action) { 2665 synchronized (mutex) {m.forEach(action);} 2666 } 2667 @Override 2668 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 2669 synchronized (mutex) {m.replaceAll(function);} 2670 } 2671 @Override 2672 public V putIfAbsent(K key, V value) { 2673 synchronized (mutex) {return m.putIfAbsent(key, value);} 2674 } 2675 @Override 2676 public boolean remove(Object key, Object value) { 2677 synchronized (mutex) {return m.remove(key, value);} 2678 } 2679 @Override 2680 public boolean replace(K key, V oldValue, V newValue) { 2681 synchronized (mutex) {return m.replace(key, oldValue, newValue);} 2682 } 2683 @Override 2684 public V replace(K key, V value) { 2685 synchronized (mutex) {return m.replace(key, value);} 2686 } 2687 @Override 2688 public V computeIfAbsent(K key, 2689 Function<? super K, ? extends V> mappingFunction) { 2690 synchronized (mutex) {return m.computeIfAbsent(key, mappingFunction);} 2691 } 2692 @Override 2693 public V computeIfPresent(K key, 2694 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 2695 synchronized (mutex) {return m.computeIfPresent(key, remappingFunction);} 2696 } 2697 @Override 2698 public V compute(K key, 2699 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 2700 synchronized (mutex) {return m.compute(key, remappingFunction);} 2701 } 2702 @Override 2703 public V merge(K key, V value, 2704 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 2705 synchronized (mutex) {return m.merge(key, value, remappingFunction);} 2706 } 2707 2708 private void writeObject(ObjectOutputStream s) throws IOException { 2709 synchronized (mutex) {s.defaultWriteObject();} 2710 } 2711 } 2712 2713 /** 2714 * Returns a synchronized (thread-safe) sorted map backed by the specified 2715 * sorted map. In order to guarantee serial access, it is critical that 2716 * <strong>all</strong> access to the backing sorted map is accomplished 2717 * through the returned sorted map (or its views).<p> 2718 * 2719 * It is imperative that the user manually synchronize on the returned 2720 * sorted map when iterating over any of its collection views, or the 2721 * collections views of any of its <tt>subMap</tt>, <tt>headMap</tt> or 2722 * <tt>tailMap</tt> views. 2723 * <pre> 2724 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); 2725 * ... 2726 * Set s = m.keySet(); // Needn't be in synchronized block 2727 * ... 2728 * synchronized (m) { // Synchronizing on m, not s! 2729 * Iterator i = s.iterator(); // Must be in synchronized block 2730 * while (i.hasNext()) 2731 * foo(i.next()); 2732 * } 2733 * </pre> 2734 * or: 2735 * <pre> 2736 * SortedMap m = Collections.synchronizedSortedMap(new TreeMap()); 2737 * SortedMap m2 = m.subMap(foo, bar); 2738 * ... 2739 * Set s2 = m2.keySet(); // Needn't be in synchronized block 2740 * ... 2741 * synchronized (m) { // Synchronizing on m, not m2 or s2! 2742 * Iterator i = s.iterator(); // Must be in synchronized block 2743 * while (i.hasNext()) 2744 * foo(i.next()); 2745 * } 2746 * </pre> 2747 * Failure to follow this advice may result in non-deterministic behavior. 2748 * 2749 * <p>The returned sorted map will be serializable if the specified 2750 * sorted map is serializable. 2751 * 2752 * @param <K> the class of the map keys 2753 * @param <V> the class of the map values 2754 * @param m the sorted map to be "wrapped" in a synchronized sorted map. 2755 * @return a synchronized view of the specified sorted map. 2756 */ 2757 public static <K,V> SortedMap<K,V> synchronizedSortedMap(SortedMap<K,V> m) { 2758 return new SynchronizedSortedMap<>(m); 2759 } 2760 2761 /** 2762 * @serial include 2763 */ 2764 static class SynchronizedSortedMap<K,V> 2765 extends SynchronizedMap<K,V> 2766 implements SortedMap<K,V> 2767 { 2768 private static final long serialVersionUID = -8798146769416483793L; 2769 2770 private final SortedMap<K,V> sm; 2771 2772 SynchronizedSortedMap(SortedMap<K,V> m) { 2773 super(m); 2774 sm = m; 2775 } 2776 SynchronizedSortedMap(SortedMap<K,V> m, Object mutex) { 2777 super(m, mutex); 2778 sm = m; 2779 } 2780 2781 public Comparator<? super K> comparator() { 2782 synchronized (mutex) {return sm.comparator();} 2783 } 2784 2785 public SortedMap<K,V> subMap(K fromKey, K toKey) { 2786 synchronized (mutex) { 2787 return new SynchronizedSortedMap<>( 2788 sm.subMap(fromKey, toKey), mutex); 2789 } 2790 } 2791 public SortedMap<K,V> headMap(K toKey) { 2792 synchronized (mutex) { 2793 return new SynchronizedSortedMap<>(sm.headMap(toKey), mutex); 2794 } 2795 } 2796 public SortedMap<K,V> tailMap(K fromKey) { 2797 synchronized (mutex) { 2798 return new SynchronizedSortedMap<>(sm.tailMap(fromKey),mutex); 2799 } 2800 } 2801 2802 public K firstKey() { 2803 synchronized (mutex) {return sm.firstKey();} 2804 } 2805 public K lastKey() { 2806 synchronized (mutex) {return sm.lastKey();} 2807 } 2808 } 2809 2810 /** 2811 * Returns a synchronized (thread-safe) navigable map backed by the 2812 * specified navigable map. In order to guarantee serial access, it is 2813 * critical that <strong>all</strong> access to the backing navigable map is 2814 * accomplished through the returned navigable map (or its views).<p> 2815 * 2816 * It is imperative that the user manually synchronize on the returned 2817 * navigable map when iterating over any of its collection views, or the 2818 * collections views of any of its {@code subMap}, {@code headMap} or 2819 * {@code tailMap} views. 2820 * <pre> 2821 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap()); 2822 * ... 2823 * Set s = m.keySet(); // Needn't be in synchronized block 2824 * ... 2825 * synchronized (m) { // Synchronizing on m, not s! 2826 * Iterator i = s.iterator(); // Must be in synchronized block 2827 * while (i.hasNext()) 2828 * foo(i.next()); 2829 * } 2830 * </pre> 2831 * or: 2832 * <pre> 2833 * NavigableMap m = Collections.synchronizedNavigableMap(new TreeMap()); 2834 * NavigableMap m2 = m.subMap(foo, true, bar, false); 2835 * ... 2836 * Set s2 = m2.keySet(); // Needn't be in synchronized block 2837 * ... 2838 * synchronized (m) { // Synchronizing on m, not m2 or s2! 2839 * Iterator i = s.iterator(); // Must be in synchronized block 2840 * while (i.hasNext()) 2841 * foo(i.next()); 2842 * } 2843 * </pre> 2844 * Failure to follow this advice may result in non-deterministic behavior. 2845 * 2846 * <p>The returned navigable map will be serializable if the specified 2847 * navigable map is serializable. 2848 * 2849 * @param <K> the class of the map keys 2850 * @param <V> the class of the map values 2851 * @param m the navigable map to be "wrapped" in a synchronized navigable 2852 * map 2853 * @return a synchronized view of the specified navigable map. 2854 * @since 1.8 2855 * @hide 2856 */ 2857 public static <K,V> NavigableMap<K,V> synchronizedNavigableMap(NavigableMap<K,V> m) { 2858 return new SynchronizedNavigableMap<>(m); 2859 } 2860 2861 /** 2862 * A synchronized NavigableMap. 2863 * 2864 * @serial include 2865 */ 2866 static class SynchronizedNavigableMap<K,V> 2867 extends SynchronizedSortedMap<K,V> 2868 implements NavigableMap<K,V> 2869 { 2870 private static final long serialVersionUID = 699392247599746807L; 2871 2872 private final NavigableMap<K,V> nm; 2873 2874 SynchronizedNavigableMap(NavigableMap<K,V> m) { 2875 super(m); 2876 nm = m; 2877 } 2878 SynchronizedNavigableMap(NavigableMap<K,V> m, Object mutex) { 2879 super(m, mutex); 2880 nm = m; 2881 } 2882 2883 public Entry<K, V> lowerEntry(K key) 2884 { synchronized (mutex) { return nm.lowerEntry(key); } } 2885 public K lowerKey(K key) 2886 { synchronized (mutex) { return nm.lowerKey(key); } } 2887 public Entry<K, V> floorEntry(K key) 2888 { synchronized (mutex) { return nm.floorEntry(key); } } 2889 public K floorKey(K key) 2890 { synchronized (mutex) { return nm.floorKey(key); } } 2891 public Entry<K, V> ceilingEntry(K key) 2892 { synchronized (mutex) { return nm.ceilingEntry(key); } } 2893 public K ceilingKey(K key) 2894 { synchronized (mutex) { return nm.ceilingKey(key); } } 2895 public Entry<K, V> higherEntry(K key) 2896 { synchronized (mutex) { return nm.higherEntry(key); } } 2897 public K higherKey(K key) 2898 { synchronized (mutex) { return nm.higherKey(key); } } 2899 public Entry<K, V> firstEntry() 2900 { synchronized (mutex) { return nm.firstEntry(); } } 2901 public Entry<K, V> lastEntry() 2902 { synchronized (mutex) { return nm.lastEntry(); } } 2903 public Entry<K, V> pollFirstEntry() 2904 { synchronized (mutex) { return nm.pollFirstEntry(); } } 2905 public Entry<K, V> pollLastEntry() 2906 { synchronized (mutex) { return nm.pollLastEntry(); } } 2907 2908 public NavigableMap<K, V> descendingMap() { 2909 synchronized (mutex) { 2910 return 2911 new SynchronizedNavigableMap<>(nm.descendingMap(), mutex); 2912 } 2913 } 2914 2915 public NavigableSet<K> keySet() { 2916 return navigableKeySet(); 2917 } 2918 2919 public NavigableSet<K> navigableKeySet() { 2920 synchronized (mutex) { 2921 return new SynchronizedNavigableSet<>(nm.navigableKeySet(), mutex); 2922 } 2923 } 2924 2925 public NavigableSet<K> descendingKeySet() { 2926 synchronized (mutex) { 2927 return new SynchronizedNavigableSet<>(nm.descendingKeySet(), mutex); 2928 } 2929 } 2930 2931 2932 public SortedMap<K,V> subMap(K fromKey, K toKey) { 2933 synchronized (mutex) { 2934 return new SynchronizedNavigableMap<>( 2935 nm.subMap(fromKey, true, toKey, false), mutex); 2936 } 2937 } 2938 public SortedMap<K,V> headMap(K toKey) { 2939 synchronized (mutex) { 2940 return new SynchronizedNavigableMap<>(nm.headMap(toKey, false), mutex); 2941 } 2942 } 2943 public SortedMap<K,V> tailMap(K fromKey) { 2944 synchronized (mutex) { 2945 return new SynchronizedNavigableMap<>(nm.tailMap(fromKey, true),mutex); 2946 } 2947 } 2948 2949 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 2950 synchronized (mutex) { 2951 return new SynchronizedNavigableMap<>( 2952 nm.subMap(fromKey, fromInclusive, toKey, toInclusive), mutex); 2953 } 2954 } 2955 2956 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) { 2957 synchronized (mutex) { 2958 return new SynchronizedNavigableMap<>( 2959 nm.headMap(toKey, inclusive), mutex); 2960 } 2961 } 2962 2963 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) { 2964 synchronized (mutex) { 2965 return new SynchronizedNavigableMap<>( 2966 nm.tailMap(fromKey, inclusive), mutex); 2967 } 2968 } 2969 } 2970 2971 // Dynamically typesafe collection wrappers 2972 2973 /** 2974 * Returns a dynamically typesafe view of the specified collection. 2975 * Any attempt to insert an element of the wrong type will result in an 2976 * immediate {@link ClassCastException}. Assuming a collection 2977 * contains no incorrectly typed elements prior to the time a 2978 * dynamically typesafe view is generated, and that all subsequent 2979 * access to the collection takes place through the view, it is 2980 * <i>guaranteed</i> that the collection cannot contain an incorrectly 2981 * typed element. 2982 * 2983 * <p>The generics mechanism in the language provides compile-time 2984 * (static) type checking, but it is possible to defeat this mechanism 2985 * with unchecked casts. Usually this is not a problem, as the compiler 2986 * issues warnings on all such unchecked operations. There are, however, 2987 * times when static type checking alone is not sufficient. For example, 2988 * suppose a collection is passed to a third-party library and it is 2989 * imperative that the library code not corrupt the collection by 2990 * inserting an element of the wrong type. 2991 * 2992 * <p>Another use of dynamically typesafe views is debugging. Suppose a 2993 * program fails with a {@code ClassCastException}, indicating that an 2994 * incorrectly typed element was put into a parameterized collection. 2995 * Unfortunately, the exception can occur at any time after the erroneous 2996 * element is inserted, so it typically provides little or no information 2997 * as to the real source of the problem. If the problem is reproducible, 2998 * one can quickly determine its source by temporarily modifying the 2999 * program to wrap the collection with a dynamically typesafe view. 3000 * For example, this declaration: 3001 * <pre> {@code 3002 * Collection<String> c = new HashSet<>(); 3003 * }</pre> 3004 * may be replaced temporarily by this one: 3005 * <pre> {@code 3006 * Collection<String> c = Collections.checkedCollection( 3007 * new HashSet<>(), String.class); 3008 * }</pre> 3009 * Running the program again will cause it to fail at the point where 3010 * an incorrectly typed element is inserted into the collection, clearly 3011 * identifying the source of the problem. Once the problem is fixed, the 3012 * modified declaration may be reverted back to the original. 3013 * 3014 * <p>The returned collection does <i>not</i> pass the hashCode and equals 3015 * operations through to the backing collection, but relies on 3016 * {@code Object}'s {@code equals} and {@code hashCode} methods. This 3017 * is necessary to preserve the contracts of these operations in the case 3018 * that the backing collection is a set or a list. 3019 * 3020 * <p>The returned collection will be serializable if the specified 3021 * collection is serializable. 3022 * 3023 * <p>Since {@code null} is considered to be a value of any reference 3024 * type, the returned collection permits insertion of null elements 3025 * whenever the backing collection does. 3026 * 3027 * @param <E> the class of the objects in the collection 3028 * @param c the collection for which a dynamically typesafe view is to be 3029 * returned 3030 * @param type the type of element that {@code c} is permitted to hold 3031 * @return a dynamically typesafe view of the specified collection 3032 * @since 1.5 3033 */ 3034 public static <E> Collection<E> checkedCollection(Collection<E> c, 3035 Class<E> type) { 3036 return new CheckedCollection<>(c, type); 3037 } 3038 3039 @SuppressWarnings("unchecked") 3040 static <T> T[] zeroLengthArray(Class<T> type) { 3041 return (T[]) Array.newInstance(type, 0); 3042 } 3043 3044 /** 3045 * @serial include 3046 */ 3047 static class CheckedCollection<E> implements Collection<E>, Serializable { 3048 private static final long serialVersionUID = 1578914078182001775L; 3049 3050 final Collection<E> c; 3051 final Class<E> type; 3052 3053 @SuppressWarnings("unchecked") 3054 E typeCheck(Object o) { 3055 if (o != null && !type.isInstance(o)) 3056 throw new ClassCastException(badElementMsg(o)); 3057 return (E) o; 3058 } 3059 3060 private String badElementMsg(Object o) { 3061 return "Attempt to insert " + o.getClass() + 3062 " element into collection with element type " + type; 3063 } 3064 3065 CheckedCollection(Collection<E> c, Class<E> type) { 3066 this.c = Objects.requireNonNull(c, "c"); 3067 this.type = Objects.requireNonNull(type, "type"); 3068 } 3069 3070 public int size() { return c.size(); } 3071 public boolean isEmpty() { return c.isEmpty(); } 3072 public boolean contains(Object o) { return c.contains(o); } 3073 public Object[] toArray() { return c.toArray(); } 3074 public <T> T[] toArray(T[] a) { return c.toArray(a); } 3075 public String toString() { return c.toString(); } 3076 public boolean remove(Object o) { return c.remove(o); } 3077 public void clear() { c.clear(); } 3078 3079 public boolean containsAll(Collection<?> coll) { 3080 return c.containsAll(coll); 3081 } 3082 public boolean removeAll(Collection<?> coll) { 3083 return c.removeAll(coll); 3084 } 3085 public boolean retainAll(Collection<?> coll) { 3086 return c.retainAll(coll); 3087 } 3088 3089 public Iterator<E> iterator() { 3090 // JDK-6363904 - unwrapped iterator could be typecast to 3091 // ListIterator with unsafe set() 3092 final Iterator<E> it = c.iterator(); 3093 return new Iterator<E>() { 3094 public boolean hasNext() { return it.hasNext(); } 3095 public E next() { return it.next(); } 3096 public void remove() { it.remove(); }}; 3097 // Android-note: Should we delegate to it for forEachRemaining ? 3098 } 3099 3100 public boolean add(E e) { return c.add(typeCheck(e)); } 3101 3102 private E[] zeroLengthElementArray; // Lazily initialized 3103 3104 private E[] zeroLengthElementArray() { 3105 return zeroLengthElementArray != null ? zeroLengthElementArray : 3106 (zeroLengthElementArray = zeroLengthArray(type)); 3107 } 3108 3109 @SuppressWarnings("unchecked") 3110 Collection<E> checkedCopyOf(Collection<? extends E> coll) { 3111 Object[] a; 3112 try { 3113 E[] z = zeroLengthElementArray(); 3114 a = coll.toArray(z); 3115 // Defend against coll violating the toArray contract 3116 if (a.getClass() != z.getClass()) 3117 a = Arrays.copyOf(a, a.length, z.getClass()); 3118 } catch (ArrayStoreException ignore) { 3119 // To get better and consistent diagnostics, 3120 // we call typeCheck explicitly on each element. 3121 // We call clone() to defend against coll retaining a 3122 // reference to the returned array and storing a bad 3123 // element into it after it has been type checked. 3124 a = coll.toArray().clone(); 3125 for (Object o : a) 3126 typeCheck(o); 3127 } 3128 // A slight abuse of the type system, but safe here. 3129 return (Collection<E>) Arrays.asList(a); 3130 } 3131 3132 public boolean addAll(Collection<? extends E> coll) { 3133 // Doing things this way insulates us from concurrent changes 3134 // in the contents of coll and provides all-or-nothing 3135 // semantics (which we wouldn't get if we type-checked each 3136 // element as we added it) 3137 return c.addAll(checkedCopyOf(coll)); 3138 } 3139 3140 // Override default methods in Collection 3141 @Override 3142 public void forEach(Consumer<? super E> action) {c.forEach(action);} 3143 @Override 3144 public boolean removeIf(Predicate<? super E> filter) { 3145 return c.removeIf(filter); 3146 } 3147 @Override 3148 public Spliterator<E> spliterator() {return c.spliterator();} 3149 @Override 3150 public Stream<E> stream() {return c.stream();} 3151 @Override 3152 public Stream<E> parallelStream() {return c.parallelStream();} 3153 } 3154 3155 /** 3156 * Returns a dynamically typesafe view of the specified queue. 3157 * Any attempt to insert an element of the wrong type will result in 3158 * an immediate {@link ClassCastException}. Assuming a queue contains 3159 * no incorrectly typed elements prior to the time a dynamically typesafe 3160 * view is generated, and that all subsequent access to the queue 3161 * takes place through the view, it is <i>guaranteed</i> that the 3162 * queue cannot contain an incorrectly typed element. 3163 * 3164 * <p>A discussion of the use of dynamically typesafe views may be 3165 * found in the documentation for the {@link #checkedCollection 3166 * checkedCollection} method. 3167 * 3168 * <p>The returned queue will be serializable if the specified queue 3169 * is serializable. 3170 * 3171 * <p>Since {@code null} is considered to be a value of any reference 3172 * type, the returned queue permits insertion of {@code null} elements 3173 * whenever the backing queue does. 3174 * 3175 * @param <E> the class of the objects in the queue 3176 * @param queue the queue for which a dynamically typesafe view is to be 3177 * returned 3178 * @param type the type of element that {@code queue} is permitted to hold 3179 * @return a dynamically typesafe view of the specified queue 3180 * @since 1.8 3181 * @hide 3182 */ 3183 public static <E> Queue<E> checkedQueue(Queue<E> queue, Class<E> type) { 3184 return new CheckedQueue<>(queue, type); 3185 } 3186 3187 /** 3188 * @serial include 3189 */ 3190 static class CheckedQueue<E> 3191 extends CheckedCollection<E> 3192 implements Queue<E>, Serializable 3193 { 3194 private static final long serialVersionUID = 1433151992604707767L; 3195 final Queue<E> queue; 3196 3197 CheckedQueue(Queue<E> queue, Class<E> elementType) { 3198 super(queue, elementType); 3199 this.queue = queue; 3200 } 3201 3202 public E element() {return queue.element();} 3203 public boolean equals(Object o) {return o == this || c.equals(o);} 3204 public int hashCode() {return c.hashCode();} 3205 public E peek() {return queue.peek();} 3206 public E poll() {return queue.poll();} 3207 public E remove() {return queue.remove();} 3208 public boolean offer(E e) {return queue.offer(typeCheck(e));} 3209 } 3210 3211 /** 3212 * Returns a dynamically typesafe view of the specified set. 3213 * Any attempt to insert an element of the wrong type will result in 3214 * an immediate {@link ClassCastException}. Assuming a set contains 3215 * no incorrectly typed elements prior to the time a dynamically typesafe 3216 * view is generated, and that all subsequent access to the set 3217 * takes place through the view, it is <i>guaranteed</i> that the 3218 * set cannot contain an incorrectly typed element. 3219 * 3220 * <p>A discussion of the use of dynamically typesafe views may be 3221 * found in the documentation for the {@link #checkedCollection 3222 * checkedCollection} method. 3223 * 3224 * <p>The returned set will be serializable if the specified set is 3225 * serializable. 3226 * 3227 * <p>Since {@code null} is considered to be a value of any reference 3228 * type, the returned set permits insertion of null elements whenever 3229 * the backing set does. 3230 * 3231 * @param <E> the class of the objects in the set 3232 * @param s the set for which a dynamically typesafe view is to be 3233 * returned 3234 * @param type the type of element that {@code s} is permitted to hold 3235 * @return a dynamically typesafe view of the specified set 3236 * @since 1.5 3237 */ 3238 public static <E> Set<E> checkedSet(Set<E> s, Class<E> type) { 3239 return new CheckedSet<>(s, type); 3240 } 3241 3242 /** 3243 * @serial include 3244 */ 3245 static class CheckedSet<E> extends CheckedCollection<E> 3246 implements Set<E>, Serializable 3247 { 3248 private static final long serialVersionUID = 4694047833775013803L; 3249 3250 CheckedSet(Set<E> s, Class<E> elementType) { super(s, elementType); } 3251 3252 public boolean equals(Object o) { return o == this || c.equals(o); } 3253 public int hashCode() { return c.hashCode(); } 3254 } 3255 3256 /** 3257 * Returns a dynamically typesafe view of the specified sorted set. 3258 * Any attempt to insert an element of the wrong type will result in an 3259 * immediate {@link ClassCastException}. Assuming a sorted set 3260 * contains no incorrectly typed elements prior to the time a 3261 * dynamically typesafe view is generated, and that all subsequent 3262 * access to the sorted set takes place through the view, it is 3263 * <i>guaranteed</i> that the sorted set cannot contain an incorrectly 3264 * typed element. 3265 * 3266 * <p>A discussion of the use of dynamically typesafe views may be 3267 * found in the documentation for the {@link #checkedCollection 3268 * checkedCollection} method. 3269 * 3270 * <p>The returned sorted set will be serializable if the specified sorted 3271 * set is serializable. 3272 * 3273 * <p>Since {@code null} is considered to be a value of any reference 3274 * type, the returned sorted set permits insertion of null elements 3275 * whenever the backing sorted set does. 3276 * 3277 * @param <E> the class of the objects in the set 3278 * @param s the sorted set for which a dynamically typesafe view is to be 3279 * returned 3280 * @param type the type of element that {@code s} is permitted to hold 3281 * @return a dynamically typesafe view of the specified sorted set 3282 * @since 1.5 3283 */ 3284 public static <E> SortedSet<E> checkedSortedSet(SortedSet<E> s, 3285 Class<E> type) { 3286 return new CheckedSortedSet<>(s, type); 3287 } 3288 3289 /** 3290 * @serial include 3291 */ 3292 static class CheckedSortedSet<E> extends CheckedSet<E> 3293 implements SortedSet<E>, Serializable 3294 { 3295 private static final long serialVersionUID = 1599911165492914959L; 3296 3297 private final SortedSet<E> ss; 3298 3299 CheckedSortedSet(SortedSet<E> s, Class<E> type) { 3300 super(s, type); 3301 ss = s; 3302 } 3303 3304 public Comparator<? super E> comparator() { return ss.comparator(); } 3305 public E first() { return ss.first(); } 3306 public E last() { return ss.last(); } 3307 3308 public SortedSet<E> subSet(E fromElement, E toElement) { 3309 return checkedSortedSet(ss.subSet(fromElement,toElement), type); 3310 } 3311 public SortedSet<E> headSet(E toElement) { 3312 return checkedSortedSet(ss.headSet(toElement), type); 3313 } 3314 public SortedSet<E> tailSet(E fromElement) { 3315 return checkedSortedSet(ss.tailSet(fromElement), type); 3316 } 3317 } 3318 3319/** 3320 * Returns a dynamically typesafe view of the specified navigable set. 3321 * Any attempt to insert an element of the wrong type will result in an 3322 * immediate {@link ClassCastException}. Assuming a navigable set 3323 * contains no incorrectly typed elements prior to the time a 3324 * dynamically typesafe view is generated, and that all subsequent 3325 * access to the navigable set takes place through the view, it is 3326 * <em>guaranteed</em> that the navigable set cannot contain an incorrectly 3327 * typed element. 3328 * 3329 * <p>A discussion of the use of dynamically typesafe views may be 3330 * found in the documentation for the {@link #checkedCollection 3331 * checkedCollection} method. 3332 * 3333 * <p>The returned navigable set will be serializable if the specified 3334 * navigable set is serializable. 3335 * 3336 * <p>Since {@code null} is considered to be a value of any reference 3337 * type, the returned navigable set permits insertion of null elements 3338 * whenever the backing sorted set does. 3339 * 3340 * @param <E> the class of the objects in the set 3341 * @param s the navigable set for which a dynamically typesafe view is to be 3342 * returned 3343 * @param type the type of element that {@code s} is permitted to hold 3344 * @return a dynamically typesafe view of the specified navigable set 3345 * @since 1.8 3346 * @hide 3347 */ 3348 public static <E> NavigableSet<E> checkedNavigableSet(NavigableSet<E> s, 3349 Class<E> type) { 3350 return new CheckedNavigableSet<>(s, type); 3351 } 3352 3353 /** 3354 * @serial include 3355 */ 3356 static class CheckedNavigableSet<E> extends CheckedSortedSet<E> 3357 implements NavigableSet<E>, Serializable 3358 { 3359 private static final long serialVersionUID = -5429120189805438922L; 3360 3361 private final NavigableSet<E> ns; 3362 3363 CheckedNavigableSet(NavigableSet<E> s, Class<E> type) { 3364 super(s, type); 3365 ns = s; 3366 } 3367 3368 public E lower(E e) { return ns.lower(e); } 3369 public E floor(E e) { return ns.floor(e); } 3370 public E ceiling(E e) { return ns.ceiling(e); } 3371 public E higher(E e) { return ns.higher(e); } 3372 public E pollFirst() { return ns.pollFirst(); } 3373 public E pollLast() {return ns.pollLast(); } 3374 public NavigableSet<E> descendingSet() 3375 { return checkedNavigableSet(ns.descendingSet(), type); } 3376 public Iterator<E> descendingIterator() 3377 {return checkedNavigableSet(ns.descendingSet(), type).iterator(); } 3378 3379 public NavigableSet<E> subSet(E fromElement, E toElement) { 3380 return checkedNavigableSet(ns.subSet(fromElement, true, toElement, false), type); 3381 } 3382 public NavigableSet<E> headSet(E toElement) { 3383 return checkedNavigableSet(ns.headSet(toElement, false), type); 3384 } 3385 public NavigableSet<E> tailSet(E fromElement) { 3386 return checkedNavigableSet(ns.tailSet(fromElement, true), type); 3387 } 3388 3389 public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) { 3390 return checkedNavigableSet(ns.subSet(fromElement, fromInclusive, toElement, toInclusive), type); 3391 } 3392 3393 public NavigableSet<E> headSet(E toElement, boolean inclusive) { 3394 return checkedNavigableSet(ns.headSet(toElement, inclusive), type); 3395 } 3396 3397 public NavigableSet<E> tailSet(E fromElement, boolean inclusive) { 3398 return checkedNavigableSet(ns.tailSet(fromElement, inclusive), type); 3399 } 3400 } 3401 3402 /** 3403 * Returns a dynamically typesafe view of the specified list. 3404 * Any attempt to insert an element of the wrong type will result in 3405 * an immediate {@link ClassCastException}. Assuming a list contains 3406 * no incorrectly typed elements prior to the time a dynamically typesafe 3407 * view is generated, and that all subsequent access to the list 3408 * takes place through the view, it is <i>guaranteed</i> that the 3409 * list cannot contain an incorrectly typed element. 3410 * 3411 * <p>A discussion of the use of dynamically typesafe views may be 3412 * found in the documentation for the {@link #checkedCollection 3413 * checkedCollection} method. 3414 * 3415 * <p>The returned list will be serializable if the specified list 3416 * is serializable. 3417 * 3418 * <p>Since {@code null} is considered to be a value of any reference 3419 * type, the returned list permits insertion of null elements whenever 3420 * the backing list does. 3421 * 3422 * @param <E> the class of the objects in the list 3423 * @param list the list for which a dynamically typesafe view is to be 3424 * returned 3425 * @param type the type of element that {@code list} is permitted to hold 3426 * @return a dynamically typesafe view of the specified list 3427 * @since 1.5 3428 */ 3429 public static <E> List<E> checkedList(List<E> list, Class<E> type) { 3430 return (list instanceof RandomAccess ? 3431 new CheckedRandomAccessList<>(list, type) : 3432 new CheckedList<>(list, type)); 3433 } 3434 3435 /** 3436 * @serial include 3437 */ 3438 static class CheckedList<E> 3439 extends CheckedCollection<E> 3440 implements List<E> 3441 { 3442 private static final long serialVersionUID = 65247728283967356L; 3443 final List<E> list; 3444 3445 CheckedList(List<E> list, Class<E> type) { 3446 super(list, type); 3447 this.list = list; 3448 } 3449 3450 public boolean equals(Object o) { return o == this || list.equals(o); } 3451 public int hashCode() { return list.hashCode(); } 3452 public E get(int index) { return list.get(index); } 3453 public E remove(int index) { return list.remove(index); } 3454 public int indexOf(Object o) { return list.indexOf(o); } 3455 public int lastIndexOf(Object o) { return list.lastIndexOf(o); } 3456 3457 public E set(int index, E element) { 3458 return list.set(index, typeCheck(element)); 3459 } 3460 3461 public void add(int index, E element) { 3462 list.add(index, typeCheck(element)); 3463 } 3464 3465 public boolean addAll(int index, Collection<? extends E> c) { 3466 return list.addAll(index, checkedCopyOf(c)); 3467 } 3468 public ListIterator<E> listIterator() { return listIterator(0); } 3469 3470 public ListIterator<E> listIterator(final int index) { 3471 final ListIterator<E> i = list.listIterator(index); 3472 3473 return new ListIterator<E>() { 3474 public boolean hasNext() { return i.hasNext(); } 3475 public E next() { return i.next(); } 3476 public boolean hasPrevious() { return i.hasPrevious(); } 3477 public E previous() { return i.previous(); } 3478 public int nextIndex() { return i.nextIndex(); } 3479 public int previousIndex() { return i.previousIndex(); } 3480 public void remove() { i.remove(); } 3481 3482 public void set(E e) { 3483 i.set(typeCheck(e)); 3484 } 3485 3486 public void add(E e) { 3487 i.add(typeCheck(e)); 3488 } 3489 3490 @Override 3491 public void forEachRemaining(Consumer<? super E> action) { 3492 i.forEachRemaining(action); 3493 } 3494 }; 3495 } 3496 3497 public List<E> subList(int fromIndex, int toIndex) { 3498 return new CheckedList<>(list.subList(fromIndex, toIndex), type); 3499 } 3500 3501 /** 3502 * {@inheritDoc} 3503 * 3504 * @throws ClassCastException if the class of an element returned by the 3505 * operator prevents it from being added to this collection. The 3506 * exception may be thrown after some elements of the list have 3507 * already been replaced. 3508 */ 3509 @Override 3510 public void replaceAll(UnaryOperator<E> operator) { 3511 Objects.requireNonNull(operator); 3512 list.replaceAll(e -> typeCheck(operator.apply(e))); 3513 } 3514 3515 @Override 3516 public void sort(Comparator<? super E> c) { 3517 list.sort(c); 3518 } 3519 } 3520 3521 /** 3522 * @serial include 3523 */ 3524 static class CheckedRandomAccessList<E> extends CheckedList<E> 3525 implements RandomAccess 3526 { 3527 private static final long serialVersionUID = 1638200125423088369L; 3528 3529 CheckedRandomAccessList(List<E> list, Class<E> type) { 3530 super(list, type); 3531 } 3532 3533 public List<E> subList(int fromIndex, int toIndex) { 3534 return new CheckedRandomAccessList<>( 3535 list.subList(fromIndex, toIndex), type); 3536 } 3537 } 3538 3539 /** 3540 * Returns a dynamically typesafe view of the specified map. 3541 * Any attempt to insert a mapping whose key or value have the wrong 3542 * type will result in an immediate {@link ClassCastException}. 3543 * Similarly, any attempt to modify the value currently associated with 3544 * a key will result in an immediate {@link ClassCastException}, 3545 * whether the modification is attempted directly through the map 3546 * itself, or through a {@link Map.Entry} instance obtained from the 3547 * map's {@link Map#entrySet() entry set} view. 3548 * 3549 * <p>Assuming a map contains no incorrectly typed keys or values 3550 * prior to the time a dynamically typesafe view is generated, and 3551 * that all subsequent access to the map takes place through the view 3552 * (or one of its collection views), it is <i>guaranteed</i> that the 3553 * map cannot contain an incorrectly typed key or value. 3554 * 3555 * <p>A discussion of the use of dynamically typesafe views may be 3556 * found in the documentation for the {@link #checkedCollection 3557 * checkedCollection} method. 3558 * 3559 * <p>The returned map will be serializable if the specified map is 3560 * serializable. 3561 * 3562 * <p>Since {@code null} is considered to be a value of any reference 3563 * type, the returned map permits insertion of null keys or values 3564 * whenever the backing map does. 3565 * 3566 * @param <K> the class of the map keys 3567 * @param <V> the class of the map values 3568 * @param m the map for which a dynamically typesafe view is to be 3569 * returned 3570 * @param keyType the type of key that {@code m} is permitted to hold 3571 * @param valueType the type of value that {@code m} is permitted to hold 3572 * @return a dynamically typesafe view of the specified map 3573 * @since 1.5 3574 */ 3575 public static <K, V> Map<K, V> checkedMap(Map<K, V> m, 3576 Class<K> keyType, 3577 Class<V> valueType) { 3578 return new CheckedMap<>(m, keyType, valueType); 3579 } 3580 3581 3582 /** 3583 * @serial include 3584 */ 3585 private static class CheckedMap<K,V> 3586 implements Map<K,V>, Serializable 3587 { 3588 private static final long serialVersionUID = 5742860141034234728L; 3589 3590 private final Map<K, V> m; 3591 final Class<K> keyType; 3592 final Class<V> valueType; 3593 3594 private void typeCheck(Object key, Object value) { 3595 if (key != null && !keyType.isInstance(key)) 3596 throw new ClassCastException(badKeyMsg(key)); 3597 3598 if (value != null && !valueType.isInstance(value)) 3599 throw new ClassCastException(badValueMsg(value)); 3600 } 3601 3602 private BiFunction<? super K, ? super V, ? extends V> typeCheck( 3603 BiFunction<? super K, ? super V, ? extends V> func) { 3604 Objects.requireNonNull(func); 3605 return (k, v) -> { 3606 V newValue = func.apply(k, v); 3607 typeCheck(k, newValue); 3608 return newValue; 3609 }; 3610 } 3611 3612 private String badKeyMsg(Object key) { 3613 return "Attempt to insert " + key.getClass() + 3614 " key into map with key type " + keyType; 3615 } 3616 3617 private String badValueMsg(Object value) { 3618 return "Attempt to insert " + value.getClass() + 3619 " value into map with value type " + valueType; 3620 } 3621 3622 CheckedMap(Map<K, V> m, Class<K> keyType, Class<V> valueType) { 3623 this.m = Objects.requireNonNull(m); 3624 this.keyType = Objects.requireNonNull(keyType); 3625 this.valueType = Objects.requireNonNull(valueType); 3626 } 3627 3628 public int size() { return m.size(); } 3629 public boolean isEmpty() { return m.isEmpty(); } 3630 public boolean containsKey(Object key) { return m.containsKey(key); } 3631 public boolean containsValue(Object v) { return m.containsValue(v); } 3632 public V get(Object key) { return m.get(key); } 3633 public V remove(Object key) { return m.remove(key); } 3634 public void clear() { m.clear(); } 3635 public Set<K> keySet() { return m.keySet(); } 3636 public Collection<V> values() { return m.values(); } 3637 public boolean equals(Object o) { return o == this || m.equals(o); } 3638 public int hashCode() { return m.hashCode(); } 3639 public String toString() { return m.toString(); } 3640 3641 public V put(K key, V value) { 3642 typeCheck(key, value); 3643 return m.put(key, value); 3644 } 3645 3646 @SuppressWarnings("unchecked") 3647 public void putAll(Map<? extends K, ? extends V> t) { 3648 // Satisfy the following goals: 3649 // - good diagnostics in case of type mismatch 3650 // - all-or-nothing semantics 3651 // - protection from malicious t 3652 // - correct behavior if t is a concurrent map 3653 Object[] entries = t.entrySet().toArray(); 3654 List<Map.Entry<K,V>> checked = new ArrayList<>(entries.length); 3655 for (Object o : entries) { 3656 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3657 Object k = e.getKey(); 3658 Object v = e.getValue(); 3659 typeCheck(k, v); 3660 checked.add( 3661 new AbstractMap.SimpleImmutableEntry<>((K)k, (V)v)); 3662 } 3663 for (Map.Entry<K,V> e : checked) 3664 m.put(e.getKey(), e.getValue()); 3665 } 3666 3667 private transient Set<Map.Entry<K,V>> entrySet; 3668 3669 public Set<Map.Entry<K,V>> entrySet() { 3670 if (entrySet==null) 3671 entrySet = new CheckedEntrySet<>(m.entrySet(), valueType); 3672 return entrySet; 3673 } 3674 3675 // Override default methods in Map 3676 @Override 3677 public void forEach(BiConsumer<? super K, ? super V> action) { 3678 m.forEach(action); 3679 } 3680 3681 @Override 3682 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 3683 m.replaceAll(typeCheck(function)); 3684 } 3685 3686 @Override 3687 public V putIfAbsent(K key, V value) { 3688 typeCheck(key, value); 3689 return m.putIfAbsent(key, value); 3690 } 3691 3692 @Override 3693 public boolean remove(Object key, Object value) { 3694 return m.remove(key, value); 3695 } 3696 3697 @Override 3698 public boolean replace(K key, V oldValue, V newValue) { 3699 typeCheck(key, newValue); 3700 return m.replace(key, oldValue, newValue); 3701 } 3702 3703 @Override 3704 public V replace(K key, V value) { 3705 typeCheck(key, value); 3706 return m.replace(key, value); 3707 } 3708 3709 @Override 3710 public V computeIfAbsent(K key, 3711 Function<? super K, ? extends V> mappingFunction) { 3712 Objects.requireNonNull(mappingFunction); 3713 return m.computeIfAbsent(key, k -> { 3714 V value = mappingFunction.apply(k); 3715 typeCheck(k, value); 3716 return value; 3717 }); 3718 } 3719 3720 @Override 3721 public V computeIfPresent(K key, 3722 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3723 return m.computeIfPresent(key, typeCheck(remappingFunction)); 3724 } 3725 3726 @Override 3727 public V compute(K key, 3728 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 3729 return m.compute(key, typeCheck(remappingFunction)); 3730 } 3731 3732 @Override 3733 public V merge(K key, V value, 3734 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 3735 Objects.requireNonNull(remappingFunction); 3736 return m.merge(key, value, (v1, v2) -> { 3737 V newValue = remappingFunction.apply(v1, v2); 3738 typeCheck(null, newValue); 3739 return newValue; 3740 }); 3741 } 3742 3743 /** 3744 * We need this class in addition to CheckedSet as Map.Entry permits 3745 * modification of the backing Map via the setValue operation. This 3746 * class is subtle: there are many possible attacks that must be 3747 * thwarted. 3748 * 3749 * @serial exclude 3750 */ 3751 static class CheckedEntrySet<K,V> implements Set<Map.Entry<K,V>> { 3752 private final Set<Map.Entry<K,V>> s; 3753 private final Class<V> valueType; 3754 3755 CheckedEntrySet(Set<Map.Entry<K, V>> s, Class<V> valueType) { 3756 this.s = s; 3757 this.valueType = valueType; 3758 } 3759 3760 public int size() { return s.size(); } 3761 public boolean isEmpty() { return s.isEmpty(); } 3762 public String toString() { return s.toString(); } 3763 public int hashCode() { return s.hashCode(); } 3764 public void clear() { s.clear(); } 3765 3766 public boolean add(Map.Entry<K, V> e) { 3767 throw new UnsupportedOperationException(); 3768 } 3769 public boolean addAll(Collection<? extends Map.Entry<K, V>> coll) { 3770 throw new UnsupportedOperationException(); 3771 } 3772 3773 public Iterator<Map.Entry<K,V>> iterator() { 3774 final Iterator<Map.Entry<K, V>> i = s.iterator(); 3775 final Class<V> valueType = this.valueType; 3776 3777 return new Iterator<Map.Entry<K,V>>() { 3778 public boolean hasNext() { return i.hasNext(); } 3779 public void remove() { i.remove(); } 3780 3781 public Map.Entry<K,V> next() { 3782 return checkedEntry(i.next(), valueType); 3783 } 3784 // Android-note: forEachRemaining is missing checks. 3785 }; 3786 } 3787 3788 @SuppressWarnings("unchecked") 3789 public Object[] toArray() { 3790 Object[] source = s.toArray(); 3791 3792 /* 3793 * Ensure that we don't get an ArrayStoreException even if 3794 * s.toArray returns an array of something other than Object 3795 */ 3796 Object[] dest = (CheckedEntry.class.isInstance( 3797 source.getClass().getComponentType()) ? source : 3798 new Object[source.length]); 3799 3800 for (int i = 0; i < source.length; i++) 3801 dest[i] = checkedEntry((Map.Entry<K,V>)source[i], 3802 valueType); 3803 return dest; 3804 } 3805 3806 @SuppressWarnings("unchecked") 3807 public <T> T[] toArray(T[] a) { 3808 // We don't pass a to s.toArray, to avoid window of 3809 // vulnerability wherein an unscrupulous multithreaded client 3810 // could get his hands on raw (unwrapped) Entries from s. 3811 T[] arr = s.toArray(a.length==0 ? a : Arrays.copyOf(a, 0)); 3812 3813 for (int i=0; i<arr.length; i++) 3814 arr[i] = (T) checkedEntry((Map.Entry<K,V>)arr[i], 3815 valueType); 3816 if (arr.length > a.length) 3817 return arr; 3818 3819 System.arraycopy(arr, 0, a, 0, arr.length); 3820 if (a.length > arr.length) 3821 a[arr.length] = null; 3822 return a; 3823 } 3824 3825 /** 3826 * This method is overridden to protect the backing set against 3827 * an object with a nefarious equals function that senses 3828 * that the equality-candidate is Map.Entry and calls its 3829 * setValue method. 3830 */ 3831 public boolean contains(Object o) { 3832 if (!(o instanceof Map.Entry)) 3833 return false; 3834 Map.Entry<?,?> e = (Map.Entry<?,?>) o; 3835 return s.contains( 3836 (e instanceof CheckedEntry) ? e : checkedEntry(e, valueType)); 3837 } 3838 3839 /** 3840 * The bulk collection methods are overridden to protect 3841 * against an unscrupulous collection whose contains(Object o) 3842 * method senses when o is a Map.Entry, and calls o.setValue. 3843 */ 3844 public boolean containsAll(Collection<?> c) { 3845 for (Object o : c) 3846 if (!contains(o)) // Invokes safe contains() above 3847 return false; 3848 return true; 3849 } 3850 3851 public boolean remove(Object o) { 3852 if (!(o instanceof Map.Entry)) 3853 return false; 3854 return s.remove(new AbstractMap.SimpleImmutableEntry 3855 <>((Map.Entry<?,?>)o)); 3856 } 3857 3858 public boolean removeAll(Collection<?> c) { 3859 return batchRemove(c, false); 3860 } 3861 public boolean retainAll(Collection<?> c) { 3862 return batchRemove(c, true); 3863 } 3864 private boolean batchRemove(Collection<?> c, boolean complement) { 3865 Objects.requireNonNull(c); 3866 boolean modified = false; 3867 Iterator<Map.Entry<K,V>> it = iterator(); 3868 while (it.hasNext()) { 3869 if (c.contains(it.next()) != complement) { 3870 it.remove(); 3871 modified = true; 3872 } 3873 } 3874 return modified; 3875 } 3876 3877 public boolean equals(Object o) { 3878 if (o == this) 3879 return true; 3880 if (!(o instanceof Set)) 3881 return false; 3882 Set<?> that = (Set<?>) o; 3883 return that.size() == s.size() 3884 && containsAll(that); // Invokes safe containsAll() above 3885 } 3886 3887 static <K,V,T> CheckedEntry<K,V,T> checkedEntry(Map.Entry<K,V> e, 3888 Class<T> valueType) { 3889 return new CheckedEntry<>(e, valueType); 3890 } 3891 3892 /** 3893 * This "wrapper class" serves two purposes: it prevents 3894 * the client from modifying the backing Map, by short-circuiting 3895 * the setValue method, and it protects the backing Map against 3896 * an ill-behaved Map.Entry that attempts to modify another 3897 * Map.Entry when asked to perform an equality check. 3898 */ 3899 private static class CheckedEntry<K,V,T> implements Map.Entry<K,V> { 3900 private final Map.Entry<K, V> e; 3901 private final Class<T> valueType; 3902 3903 CheckedEntry(Map.Entry<K, V> e, Class<T> valueType) { 3904 this.e = Objects.requireNonNull(e); 3905 this.valueType = Objects.requireNonNull(valueType); 3906 } 3907 3908 public K getKey() { return e.getKey(); } 3909 public V getValue() { return e.getValue(); } 3910 public int hashCode() { return e.hashCode(); } 3911 public String toString() { return e.toString(); } 3912 3913 public V setValue(V value) { 3914 if (value != null && !valueType.isInstance(value)) 3915 throw new ClassCastException(badValueMsg(value)); 3916 return e.setValue(value); 3917 } 3918 3919 private String badValueMsg(Object value) { 3920 return "Attempt to insert " + value.getClass() + 3921 " value into map with value type " + valueType; 3922 } 3923 3924 public boolean equals(Object o) { 3925 if (o == this) 3926 return true; 3927 if (!(o instanceof Map.Entry)) 3928 return false; 3929 return e.equals(new AbstractMap.SimpleImmutableEntry 3930 <>((Map.Entry<?,?>)o)); 3931 } 3932 } 3933 } 3934 } 3935 3936 /** 3937 * Returns a dynamically typesafe view of the specified sorted map. 3938 * Any attempt to insert a mapping whose key or value have the wrong 3939 * type will result in an immediate {@link ClassCastException}. 3940 * Similarly, any attempt to modify the value currently associated with 3941 * a key will result in an immediate {@link ClassCastException}, 3942 * whether the modification is attempted directly through the map 3943 * itself, or through a {@link Map.Entry} instance obtained from the 3944 * map's {@link Map#entrySet() entry set} view. 3945 * 3946 * <p>Assuming a map contains no incorrectly typed keys or values 3947 * prior to the time a dynamically typesafe view is generated, and 3948 * that all subsequent access to the map takes place through the view 3949 * (or one of its collection views), it is <i>guaranteed</i> that the 3950 * map cannot contain an incorrectly typed key or value. 3951 * 3952 * <p>A discussion of the use of dynamically typesafe views may be 3953 * found in the documentation for the {@link #checkedCollection 3954 * checkedCollection} method. 3955 * 3956 * <p>The returned map will be serializable if the specified map is 3957 * serializable. 3958 * 3959 * <p>Since {@code null} is considered to be a value of any reference 3960 * type, the returned map permits insertion of null keys or values 3961 * whenever the backing map does. 3962 * 3963 * @param <K> the class of the map keys 3964 * @param <V> the class of the map values 3965 * @param m the map for which a dynamically typesafe view is to be 3966 * returned 3967 * @param keyType the type of key that {@code m} is permitted to hold 3968 * @param valueType the type of value that {@code m} is permitted to hold 3969 * @return a dynamically typesafe view of the specified map 3970 * @since 1.5 3971 */ 3972 public static <K,V> SortedMap<K,V> checkedSortedMap(SortedMap<K, V> m, 3973 Class<K> keyType, 3974 Class<V> valueType) { 3975 return new CheckedSortedMap<>(m, keyType, valueType); 3976 } 3977 3978 /** 3979 * @serial include 3980 */ 3981 static class CheckedSortedMap<K,V> extends CheckedMap<K,V> 3982 implements SortedMap<K,V>, Serializable 3983 { 3984 private static final long serialVersionUID = 1599671320688067438L; 3985 3986 private final SortedMap<K, V> sm; 3987 3988 CheckedSortedMap(SortedMap<K, V> m, 3989 Class<K> keyType, Class<V> valueType) { 3990 super(m, keyType, valueType); 3991 sm = m; 3992 } 3993 3994 public Comparator<? super K> comparator() { return sm.comparator(); } 3995 public K firstKey() { return sm.firstKey(); } 3996 public K lastKey() { return sm.lastKey(); } 3997 3998 public SortedMap<K,V> subMap(K fromKey, K toKey) { 3999 return checkedSortedMap(sm.subMap(fromKey, toKey), 4000 keyType, valueType); 4001 } 4002 public SortedMap<K,V> headMap(K toKey) { 4003 return checkedSortedMap(sm.headMap(toKey), keyType, valueType); 4004 } 4005 public SortedMap<K,V> tailMap(K fromKey) { 4006 return checkedSortedMap(sm.tailMap(fromKey), keyType, valueType); 4007 } 4008 } 4009 4010 /** 4011 * Returns a dynamically typesafe view of the specified navigable map. 4012 * Any attempt to insert a mapping whose key or value have the wrong 4013 * type will result in an immediate {@link ClassCastException}. 4014 * Similarly, any attempt to modify the value currently associated with 4015 * a key will result in an immediate {@link ClassCastException}, 4016 * whether the modification is attempted directly through the map 4017 * itself, or through a {@link Map.Entry} instance obtained from the 4018 * map's {@link Map#entrySet() entry set} view. 4019 * 4020 * <p>Assuming a map contains no incorrectly typed keys or values 4021 * prior to the time a dynamically typesafe view is generated, and 4022 * that all subsequent access to the map takes place through the view 4023 * (or one of its collection views), it is <em>guaranteed</em> that the 4024 * map cannot contain an incorrectly typed key or value. 4025 * 4026 * <p>A discussion of the use of dynamically typesafe views may be 4027 * found in the documentation for the {@link #checkedCollection 4028 * checkedCollection} method. 4029 * 4030 * <p>The returned map will be serializable if the specified map is 4031 * serializable. 4032 * 4033 * <p>Since {@code null} is considered to be a value of any reference 4034 * type, the returned map permits insertion of null keys or values 4035 * whenever the backing map does. 4036 * 4037 * @param <K> type of map keys 4038 * @param <V> type of map values 4039 * @param m the map for which a dynamically typesafe view is to be 4040 * returned 4041 * @param keyType the type of key that {@code m} is permitted to hold 4042 * @param valueType the type of value that {@code m} is permitted to hold 4043 * @return a dynamically typesafe view of the specified map 4044 * @since 1.8 4045 * @hide 4046 */ 4047 public static <K,V> NavigableMap<K,V> checkedNavigableMap(NavigableMap<K, V> m, 4048 Class<K> keyType, 4049 Class<V> valueType) { 4050 return new CheckedNavigableMap<>(m, keyType, valueType); 4051 } 4052 4053 /** 4054 * @serial include 4055 */ 4056 static class CheckedNavigableMap<K,V> extends CheckedSortedMap<K,V> 4057 implements NavigableMap<K,V>, Serializable 4058 { 4059 private static final long serialVersionUID = -4852462692372534096L; 4060 4061 private final NavigableMap<K, V> nm; 4062 4063 CheckedNavigableMap(NavigableMap<K, V> m, 4064 Class<K> keyType, Class<V> valueType) { 4065 super(m, keyType, valueType); 4066 nm = m; 4067 } 4068 4069 public Comparator<? super K> comparator() { return nm.comparator(); } 4070 public K firstKey() { return nm.firstKey(); } 4071 public K lastKey() { return nm.lastKey(); } 4072 4073 public Entry<K, V> lowerEntry(K key) { 4074 Entry<K,V> lower = nm.lowerEntry(key); 4075 return (null != lower) 4076 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(lower, valueType) 4077 : null; 4078 } 4079 4080 public K lowerKey(K key) { return nm.lowerKey(key); } 4081 4082 public Entry<K, V> floorEntry(K key) { 4083 Entry<K,V> floor = nm.floorEntry(key); 4084 return (null != floor) 4085 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(floor, valueType) 4086 : null; 4087 } 4088 4089 public K floorKey(K key) { return nm.floorKey(key); } 4090 4091 public Entry<K, V> ceilingEntry(K key) { 4092 Entry<K,V> ceiling = nm.ceilingEntry(key); 4093 return (null != ceiling) 4094 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(ceiling, valueType) 4095 : null; 4096 } 4097 4098 public K ceilingKey(K key) { return nm.ceilingKey(key); } 4099 4100 public Entry<K, V> higherEntry(K key) { 4101 Entry<K,V> higher = nm.higherEntry(key); 4102 return (null != higher) 4103 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(higher, valueType) 4104 : null; 4105 } 4106 4107 public K higherKey(K key) { return nm.higherKey(key); } 4108 4109 public Entry<K, V> firstEntry() { 4110 Entry<K,V> first = nm.firstEntry(); 4111 return (null != first) 4112 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(first, valueType) 4113 : null; 4114 } 4115 4116 public Entry<K, V> lastEntry() { 4117 Entry<K,V> last = nm.lastEntry(); 4118 return (null != last) 4119 ? new CheckedMap.CheckedEntrySet.CheckedEntry<>(last, valueType) 4120 : null; 4121 } 4122 4123 public Entry<K, V> pollFirstEntry() { 4124 Entry<K,V> entry = nm.pollFirstEntry(); 4125 return (null == entry) 4126 ? null 4127 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4128 } 4129 4130 public Entry<K, V> pollLastEntry() { 4131 Entry<K,V> entry = nm.pollLastEntry(); 4132 return (null == entry) 4133 ? null 4134 : new CheckedMap.CheckedEntrySet.CheckedEntry<>(entry, valueType); 4135 } 4136 4137 public NavigableMap<K, V> descendingMap() { 4138 return checkedNavigableMap(nm.descendingMap(), keyType, valueType); 4139 } 4140 4141 public NavigableSet<K> keySet() { 4142 return navigableKeySet(); 4143 } 4144 4145 public NavigableSet<K> navigableKeySet() { 4146 return checkedNavigableSet(nm.navigableKeySet(), keyType); 4147 } 4148 4149 public NavigableSet<K> descendingKeySet() { 4150 return checkedNavigableSet(nm.descendingKeySet(), keyType); 4151 } 4152 4153 @Override 4154 public NavigableMap<K,V> subMap(K fromKey, K toKey) { 4155 return checkedNavigableMap(nm.subMap(fromKey, true, toKey, false), 4156 keyType, valueType); 4157 } 4158 4159 @Override 4160 public NavigableMap<K,V> headMap(K toKey) { 4161 return checkedNavigableMap(nm.headMap(toKey, false), keyType, valueType); 4162 } 4163 4164 @Override 4165 public NavigableMap<K,V> tailMap(K fromKey) { 4166 return checkedNavigableMap(nm.tailMap(fromKey, true), keyType, valueType); 4167 } 4168 4169 public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) { 4170 return checkedNavigableMap(nm.subMap(fromKey, fromInclusive, toKey, toInclusive), keyType, valueType); 4171 } 4172 4173 public NavigableMap<K, V> headMap(K toKey, boolean inclusive) { 4174 return checkedNavigableMap(nm.headMap(toKey, inclusive), keyType, valueType); 4175 } 4176 4177 public NavigableMap<K, V> tailMap(K fromKey, boolean inclusive) { 4178 return checkedNavigableMap(nm.tailMap(fromKey, inclusive), keyType, valueType); 4179 } 4180 } 4181 4182 // Empty collections 4183 4184 /** 4185 * Returns an iterator that has no elements. More precisely, 4186 * 4187 * <ul> 4188 * <li>{@link Iterator#hasNext hasNext} always returns {@code 4189 * false}.</li> 4190 * <li>{@link Iterator#next next} always throws {@link 4191 * NoSuchElementException}.</li> 4192 * <li>{@link Iterator#remove remove} always throws {@link 4193 * IllegalStateException}.</li> 4194 * </ul> 4195 * 4196 * <p>Implementations of this method are permitted, but not 4197 * required, to return the same object from multiple invocations. 4198 * 4199 * @param <T> type of elements, if there were any, in the iterator 4200 * @return an empty iterator 4201 * @since 1.7 4202 */ 4203 @SuppressWarnings("unchecked") 4204 public static <T> Iterator<T> emptyIterator() { 4205 return (Iterator<T>) EmptyIterator.EMPTY_ITERATOR; 4206 } 4207 4208 private static class EmptyIterator<E> implements Iterator<E> { 4209 static final EmptyIterator<Object> EMPTY_ITERATOR 4210 = new EmptyIterator<>(); 4211 4212 public boolean hasNext() { return false; } 4213 public E next() { throw new NoSuchElementException(); } 4214 public void remove() { throw new IllegalStateException(); } 4215 @Override 4216 public void forEachRemaining(Consumer<? super E> action) { 4217 Objects.requireNonNull(action); 4218 } 4219 } 4220 4221 /** 4222 * Returns a list iterator that has no elements. More precisely, 4223 * 4224 * <ul> 4225 * <li>{@link Iterator#hasNext hasNext} and {@link 4226 * ListIterator#hasPrevious hasPrevious} always return {@code 4227 * false}.</li> 4228 * <li>{@link Iterator#next next} and {@link ListIterator#previous 4229 * previous} always throw {@link NoSuchElementException}.</li> 4230 * <li>{@link Iterator#remove remove} and {@link ListIterator#set 4231 * set} always throw {@link IllegalStateException}.</li> 4232 * <li>{@link ListIterator#add add} always throws {@link 4233 * UnsupportedOperationException}.</li> 4234 * <li>{@link ListIterator#nextIndex nextIndex} always returns 4235 * {@code 0}.</li> 4236 * <li>{@link ListIterator#previousIndex previousIndex} always 4237 * returns {@code -1}.</li> 4238 * </ul> 4239 * 4240 * <p>Implementations of this method are permitted, but not 4241 * required, to return the same object from multiple invocations. 4242 * 4243 * @param <T> type of elements, if there were any, in the iterator 4244 * @return an empty list iterator 4245 * @since 1.7 4246 */ 4247 @SuppressWarnings("unchecked") 4248 public static <T> ListIterator<T> emptyListIterator() { 4249 return (ListIterator<T>) EmptyListIterator.EMPTY_ITERATOR; 4250 } 4251 4252 private static class EmptyListIterator<E> 4253 extends EmptyIterator<E> 4254 implements ListIterator<E> 4255 { 4256 static final EmptyListIterator<Object> EMPTY_ITERATOR 4257 = new EmptyListIterator<>(); 4258 4259 public boolean hasPrevious() { return false; } 4260 public E previous() { throw new NoSuchElementException(); } 4261 public int nextIndex() { return 0; } 4262 public int previousIndex() { return -1; } 4263 public void set(E e) { throw new IllegalStateException(); } 4264 public void add(E e) { throw new UnsupportedOperationException(); } 4265 } 4266 4267 /** 4268 * Returns an enumeration that has no elements. More precisely, 4269 * 4270 * <ul> 4271 * <li>{@link Enumeration#hasMoreElements hasMoreElements} always 4272 * returns {@code false}.</li> 4273 * <li> {@link Enumeration#nextElement nextElement} always throws 4274 * {@link NoSuchElementException}.</li> 4275 * </ul> 4276 * 4277 * <p>Implementations of this method are permitted, but not 4278 * required, to return the same object from multiple invocations. 4279 * 4280 * @param <T> the class of the objects in the enumeration 4281 * @return an empty enumeration 4282 * @since 1.7 4283 */ 4284 @SuppressWarnings("unchecked") 4285 public static <T> Enumeration<T> emptyEnumeration() { 4286 return (Enumeration<T>) EmptyEnumeration.EMPTY_ENUMERATION; 4287 } 4288 4289 private static class EmptyEnumeration<E> implements Enumeration<E> { 4290 static final EmptyEnumeration<Object> EMPTY_ENUMERATION 4291 = new EmptyEnumeration<>(); 4292 4293 public boolean hasMoreElements() { return false; } 4294 public E nextElement() { throw new NoSuchElementException(); } 4295 } 4296 4297 /** 4298 * The empty set (immutable). This set is serializable. 4299 * 4300 * @see #emptySet() 4301 */ 4302 @SuppressWarnings("rawtypes") 4303 public static final Set EMPTY_SET = new EmptySet<>(); 4304 4305 /** 4306 * Returns an empty set (immutable). This set is serializable. 4307 * Unlike the like-named field, this method is parameterized. 4308 * 4309 * <p>This example illustrates the type-safe way to obtain an empty set: 4310 * <pre> 4311 * Set<String> s = Collections.emptySet(); 4312 * </pre> 4313 * @implNote Implementations of this method need not create a separate 4314 * {@code Set} object for each call. Using this method is likely to have 4315 * comparable cost to using the like-named field. (Unlike this method, the 4316 * field does not provide type safety.) 4317 * 4318 * @param <T> the class of the objects in the set 4319 * @return the empty set 4320 * 4321 * @see #EMPTY_SET 4322 * @since 1.5 4323 */ 4324 @SuppressWarnings("unchecked") 4325 public static final <T> Set<T> emptySet() { 4326 return (Set<T>) EMPTY_SET; 4327 } 4328 4329 /** 4330 * @serial include 4331 */ 4332 private static class EmptySet<E> 4333 extends AbstractSet<E> 4334 implements Serializable 4335 { 4336 private static final long serialVersionUID = 1582296315990362920L; 4337 4338 public Iterator<E> iterator() { return emptyIterator(); } 4339 4340 public int size() {return 0;} 4341 public boolean isEmpty() {return true;} 4342 4343 public boolean contains(Object obj) {return false;} 4344 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4345 4346 public Object[] toArray() { return new Object[0]; } 4347 4348 public <T> T[] toArray(T[] a) { 4349 if (a.length > 0) 4350 a[0] = null; 4351 return a; 4352 } 4353 4354 // Override default methods in Collection 4355 @Override 4356 public void forEach(Consumer<? super E> action) { 4357 Objects.requireNonNull(action); 4358 } 4359 @Override 4360 public boolean removeIf(Predicate<? super E> filter) { 4361 Objects.requireNonNull(filter); 4362 return false; 4363 } 4364 @Override 4365 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4366 4367 // Preserves singleton property 4368 private Object readResolve() { 4369 return EMPTY_SET; 4370 } 4371 } 4372 4373 /** 4374 * Returns an empty sorted set (immutable). This set is serializable. 4375 * 4376 * <p>This example illustrates the type-safe way to obtain an empty 4377 * sorted set: 4378 * <pre> {@code 4379 * SortedSet<String> s = Collections.emptySortedSet(); 4380 * }</pre> 4381 * 4382 * @implNote Implementations of this method need not create a separate 4383 * {@code SortedSet} object for each call. 4384 * 4385 * @param <E> type of elements, if there were any, in the set 4386 * @return the empty sorted set 4387 * @since 1.8 4388 * @hide 4389 */ 4390 @SuppressWarnings("unchecked") 4391 public static <E> SortedSet<E> emptySortedSet() { 4392 return (SortedSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4393 } 4394 4395 /** 4396 * Returns an empty navigable set (immutable). This set is serializable. 4397 * 4398 * <p>This example illustrates the type-safe way to obtain an empty 4399 * navigable set: 4400 * <pre> {@code 4401 * NavigableSet<String> s = Collections.emptyNavigableSet(); 4402 * }</pre> 4403 * 4404 * @implNote Implementations of this method need not 4405 * create a separate {@code NavigableSet} object for each call. 4406 * 4407 * @param <E> type of elements, if there were any, in the set 4408 * @return the empty navigable set 4409 * @since 1.8 4410 * @hide 4411 */ 4412 @SuppressWarnings("unchecked") 4413 public static <E> NavigableSet<E> emptyNavigableSet() { 4414 return (NavigableSet<E>) UnmodifiableNavigableSet.EMPTY_NAVIGABLE_SET; 4415 } 4416 4417 /** 4418 * The empty list (immutable). This list is serializable. 4419 * 4420 * @see #emptyList() 4421 */ 4422 @SuppressWarnings("rawtypes") 4423 public static final List EMPTY_LIST = new EmptyList<>(); 4424 4425 /** 4426 * Returns an empty list (immutable). This list is serializable. 4427 * 4428 * <p>This example illustrates the type-safe way to obtain an empty list: 4429 * <pre> 4430 * List<String> s = Collections.emptyList(); 4431 * </pre> 4432 * 4433 * @implNote 4434 * Implementations of this method need not create a separate <tt>List</tt> 4435 * object for each call. Using this method is likely to have comparable 4436 * cost to using the like-named field. (Unlike this method, the field does 4437 * not provide type safety.) 4438 * 4439 * @param <T> type of elements, if there were any, in the list 4440 * @return an empty immutable list 4441 * 4442 * @see #EMPTY_LIST 4443 * @since 1.5 4444 */ 4445 @SuppressWarnings("unchecked") 4446 public static final <T> List<T> emptyList() { 4447 return (List<T>) EMPTY_LIST; 4448 } 4449 4450 /** 4451 * @serial include 4452 */ 4453 private static class EmptyList<E> 4454 extends AbstractList<E> 4455 implements RandomAccess, Serializable { 4456 private static final long serialVersionUID = 8842843931221139166L; 4457 4458 public Iterator<E> iterator() { 4459 return emptyIterator(); 4460 } 4461 public ListIterator<E> listIterator() { 4462 return emptyListIterator(); 4463 } 4464 4465 public int size() {return 0;} 4466 public boolean isEmpty() {return true;} 4467 4468 public boolean contains(Object obj) {return false;} 4469 public boolean containsAll(Collection<?> c) { return c.isEmpty(); } 4470 4471 public Object[] toArray() { return new Object[0]; } 4472 4473 public <T> T[] toArray(T[] a) { 4474 if (a.length > 0) 4475 a[0] = null; 4476 return a; 4477 } 4478 4479 public E get(int index) { 4480 throw new IndexOutOfBoundsException("Index: "+index); 4481 } 4482 4483 public boolean equals(Object o) { 4484 return (o instanceof List) && ((List<?>)o).isEmpty(); 4485 } 4486 4487 public int hashCode() { return 1; } 4488 4489 @Override 4490 public boolean removeIf(Predicate<? super E> filter) { 4491 Objects.requireNonNull(filter); 4492 return false; 4493 } 4494 @Override 4495 public void replaceAll(UnaryOperator<E> operator) { 4496 Objects.requireNonNull(operator); 4497 } 4498 @Override 4499 public void sort(Comparator<? super E> c) { 4500 } 4501 4502 // Override default methods in Collection 4503 @Override 4504 public void forEach(Consumer<? super E> action) { 4505 Objects.requireNonNull(action); 4506 } 4507 4508 @Override 4509 public Spliterator<E> spliterator() { return Spliterators.emptySpliterator(); } 4510 4511 // Preserves singleton property 4512 private Object readResolve() { 4513 return EMPTY_LIST; 4514 } 4515 } 4516 4517 /** 4518 * The empty map (immutable). This map is serializable. 4519 * 4520 * @see #emptyMap() 4521 * @since 1.3 4522 */ 4523 @SuppressWarnings("rawtypes") 4524 public static final Map EMPTY_MAP = new EmptyMap<>(); 4525 4526 /** 4527 * Returns an empty map (immutable). This map is serializable. 4528 * 4529 * <p>This example illustrates the type-safe way to obtain an empty map: 4530 * <pre> 4531 * Map<String, Date> s = Collections.emptyMap(); 4532 * </pre> 4533 * @implNote Implementations of this method need not create a separate 4534 * {@code Map} object for each call. Using this method is likely to have 4535 * comparable cost to using the like-named field. (Unlike this method, the 4536 * field does not provide type safety.) 4537 * 4538 * @param <K> the class of the map keys 4539 * @param <V> the class of the map values 4540 * @return an empty map 4541 * @see #EMPTY_MAP 4542 * @since 1.5 4543 */ 4544 @SuppressWarnings("unchecked") 4545 public static final <K,V> Map<K,V> emptyMap() { 4546 return (Map<K,V>) EMPTY_MAP; 4547 } 4548 4549 /** 4550 * Returns an empty sorted map (immutable). This map is serializable. 4551 * 4552 * <p>This example illustrates the type-safe way to obtain an empty map: 4553 * <pre> {@code 4554 * SortedMap<String, Date> s = Collections.emptySortedMap(); 4555 * }</pre> 4556 * 4557 * @implNote Implementations of this method need not create a separate 4558 * {@code SortedMap} object for each call. 4559 * 4560 * @param <K> the class of the map keys 4561 * @param <V> the class of the map values 4562 * @return an empty sorted map 4563 * @since 1.8 4564 * @hide 4565 */ 4566 @SuppressWarnings("unchecked") 4567 public static final <K,V> SortedMap<K,V> emptySortedMap() { 4568 return (SortedMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4569 } 4570 4571 /** 4572 * Returns an empty navigable map (immutable). This map is serializable. 4573 * 4574 * <p>This example illustrates the type-safe way to obtain an empty map: 4575 * <pre> {@code 4576 * NavigableMap<String, Date> s = Collections.emptyNavigableMap(); 4577 * }</pre> 4578 * 4579 * @implNote Implementations of this method need not create a separate 4580 * {@code NavigableMap} object for each call. 4581 * 4582 * @param <K> the class of the map keys 4583 * @param <V> the class of the map values 4584 * @return an empty navigable map 4585 * @since 1.8 4586 * @hide 4587 */ 4588 @SuppressWarnings("unchecked") 4589 public static final <K,V> NavigableMap<K,V> emptyNavigableMap() { 4590 return (NavigableMap<K,V>) UnmodifiableNavigableMap.EMPTY_NAVIGABLE_MAP; 4591 } 4592 4593 /** 4594 * @serial include 4595 */ 4596 private static class EmptyMap<K,V> 4597 extends AbstractMap<K,V> 4598 implements Serializable 4599 { 4600 private static final long serialVersionUID = 6428348081105594320L; 4601 4602 public int size() {return 0;} 4603 public boolean isEmpty() {return true;} 4604 public boolean containsKey(Object key) {return false;} 4605 public boolean containsValue(Object value) {return false;} 4606 public V get(Object key) {return null;} 4607 public Set<K> keySet() {return emptySet();} 4608 public Collection<V> values() {return emptySet();} 4609 public Set<Map.Entry<K,V>> entrySet() {return emptySet();} 4610 4611 public boolean equals(Object o) { 4612 return (o instanceof Map) && ((Map<?,?>)o).isEmpty(); 4613 } 4614 4615 public int hashCode() {return 0;} 4616 4617 // Override default methods in Map 4618 @Override 4619 @SuppressWarnings("unchecked") 4620 public V getOrDefault(Object k, V defaultValue) { 4621 return defaultValue; 4622 } 4623 4624 @Override 4625 public void forEach(BiConsumer<? super K, ? super V> action) { 4626 Objects.requireNonNull(action); 4627 } 4628 4629 @Override 4630 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4631 Objects.requireNonNull(function); 4632 } 4633 4634 @Override 4635 public V putIfAbsent(K key, V value) { 4636 throw new UnsupportedOperationException(); 4637 } 4638 4639 @Override 4640 public boolean remove(Object key, Object value) { 4641 throw new UnsupportedOperationException(); 4642 } 4643 4644 @Override 4645 public boolean replace(K key, V oldValue, V newValue) { 4646 throw new UnsupportedOperationException(); 4647 } 4648 4649 @Override 4650 public V replace(K key, V value) { 4651 throw new UnsupportedOperationException(); 4652 } 4653 4654 @Override 4655 public V computeIfAbsent(K key, 4656 Function<? super K, ? extends V> mappingFunction) { 4657 throw new UnsupportedOperationException(); 4658 } 4659 4660 @Override 4661 public V computeIfPresent(K key, 4662 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4663 throw new UnsupportedOperationException(); 4664 } 4665 4666 @Override 4667 public V compute(K key, 4668 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4669 throw new UnsupportedOperationException(); 4670 } 4671 4672 @Override 4673 public V merge(K key, V value, 4674 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 4675 throw new UnsupportedOperationException(); 4676 } 4677 4678 // Preserves singleton property 4679 private Object readResolve() { 4680 return EMPTY_MAP; 4681 } 4682 } 4683 4684 // Singleton collections 4685 4686 /** 4687 * Returns an immutable set containing only the specified object. 4688 * The returned set is serializable. 4689 * 4690 * @param <T> the class of the objects in the set 4691 * @param o the sole object to be stored in the returned set. 4692 * @return an immutable set containing only the specified object. 4693 */ 4694 public static <T> Set<T> singleton(T o) { 4695 return new SingletonSet<>(o); 4696 } 4697 4698 static <E> Iterator<E> singletonIterator(final E e) { 4699 return new Iterator<E>() { 4700 private boolean hasNext = true; 4701 public boolean hasNext() { 4702 return hasNext; 4703 } 4704 public E next() { 4705 if (hasNext) { 4706 hasNext = false; 4707 return e; 4708 } 4709 throw new NoSuchElementException(); 4710 } 4711 public void remove() { 4712 throw new UnsupportedOperationException(); 4713 } 4714 @Override 4715 public void forEachRemaining(Consumer<? super E> action) { 4716 Objects.requireNonNull(action); 4717 if (hasNext) { 4718 action.accept(e); 4719 hasNext = false; 4720 } 4721 } 4722 }; 4723 } 4724 4725 /** 4726 * Creates a {@code Spliterator} with only the specified element 4727 * 4728 * @param <T> Type of elements 4729 * @return A singleton {@code Spliterator} 4730 */ 4731 static <T> Spliterator<T> singletonSpliterator(final T element) { 4732 return new Spliterator<T>() { 4733 long est = 1; 4734 4735 @Override 4736 public Spliterator<T> trySplit() { 4737 return null; 4738 } 4739 4740 @Override 4741 public boolean tryAdvance(Consumer<? super T> consumer) { 4742 Objects.requireNonNull(consumer); 4743 if (est > 0) { 4744 est--; 4745 consumer.accept(element); 4746 return true; 4747 } 4748 return false; 4749 } 4750 4751 @Override 4752 public void forEachRemaining(Consumer<? super T> consumer) { 4753 tryAdvance(consumer); 4754 } 4755 4756 @Override 4757 public long estimateSize() { 4758 return est; 4759 } 4760 4761 @Override 4762 public int characteristics() { 4763 int value = (element != null) ? Spliterator.NONNULL : 0; 4764 4765 return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE | 4766 Spliterator.DISTINCT | Spliterator.ORDERED; 4767 } 4768 }; 4769 } 4770 4771 /** 4772 * @serial include 4773 */ 4774 private static class SingletonSet<E> 4775 extends AbstractSet<E> 4776 implements Serializable 4777 { 4778 private static final long serialVersionUID = 3193687207550431679L; 4779 4780 private final E element; 4781 4782 SingletonSet(E e) {element = e;} 4783 4784 public Iterator<E> iterator() { 4785 return singletonIterator(element); 4786 } 4787 4788 public int size() {return 1;} 4789 4790 public boolean contains(Object o) {return eq(o, element);} 4791 4792 // Override default methods for Collection 4793 @Override 4794 public void forEach(Consumer<? super E> action) { 4795 action.accept(element); 4796 } 4797 @Override 4798 public Spliterator<E> spliterator() { 4799 return singletonSpliterator(element); 4800 } 4801 @Override 4802 public boolean removeIf(Predicate<? super E> filter) { 4803 throw new UnsupportedOperationException(); 4804 } 4805 } 4806 4807 /** 4808 * Returns an immutable list containing only the specified object. 4809 * The returned list is serializable. 4810 * 4811 * @param <T> the class of the objects in the list 4812 * @param o the sole object to be stored in the returned list. 4813 * @return an immutable list containing only the specified object. 4814 * @since 1.3 4815 */ 4816 public static <T> List<T> singletonList(T o) { 4817 return new SingletonList<>(o); 4818 } 4819 4820 /** 4821 * @serial include 4822 */ 4823 private static class SingletonList<E> 4824 extends AbstractList<E> 4825 implements RandomAccess, Serializable { 4826 4827 private static final long serialVersionUID = 3093736618740652951L; 4828 4829 private final E element; 4830 4831 SingletonList(E obj) {element = obj;} 4832 4833 public Iterator<E> iterator() { 4834 return singletonIterator(element); 4835 } 4836 4837 public int size() {return 1;} 4838 4839 public boolean contains(Object obj) {return eq(obj, element);} 4840 4841 public E get(int index) { 4842 if (index != 0) 4843 throw new IndexOutOfBoundsException("Index: "+index+", Size: 1"); 4844 return element; 4845 } 4846 4847 // Override default methods for Collection 4848 @Override 4849 public void forEach(Consumer<? super E> action) { 4850 action.accept(element); 4851 } 4852 @Override 4853 public boolean removeIf(Predicate<? super E> filter) { 4854 throw new UnsupportedOperationException(); 4855 } 4856 @Override 4857 public void replaceAll(UnaryOperator<E> operator) { 4858 throw new UnsupportedOperationException(); 4859 } 4860 @Override 4861 public void sort(Comparator<? super E> c) { 4862 } 4863 @Override 4864 public Spliterator<E> spliterator() { 4865 return singletonSpliterator(element); 4866 } 4867 } 4868 4869 /** 4870 * Returns an immutable map, mapping only the specified key to the 4871 * specified value. The returned map is serializable. 4872 * 4873 * @param <K> the class of the map keys 4874 * @param <V> the class of the map values 4875 * @param key the sole key to be stored in the returned map. 4876 * @param value the value to which the returned map maps <tt>key</tt>. 4877 * @return an immutable map containing only the specified key-value 4878 * mapping. 4879 * @since 1.3 4880 */ 4881 public static <K,V> Map<K,V> singletonMap(K key, V value) { 4882 return new SingletonMap<>(key, value); 4883 } 4884 4885 /** 4886 * @serial include 4887 */ 4888 private static class SingletonMap<K,V> 4889 extends AbstractMap<K,V> 4890 implements Serializable { 4891 private static final long serialVersionUID = -6979724477215052911L; 4892 4893 private final K k; 4894 private final V v; 4895 4896 SingletonMap(K key, V value) { 4897 k = key; 4898 v = value; 4899 } 4900 4901 public int size() {return 1;} 4902 public boolean isEmpty() {return false;} 4903 public boolean containsKey(Object key) {return eq(key, k);} 4904 public boolean containsValue(Object value) {return eq(value, v);} 4905 public V get(Object key) {return (eq(key, k) ? v : null);} 4906 4907 private transient Set<K> keySet; 4908 private transient Set<Map.Entry<K,V>> entrySet; 4909 private transient Collection<V> values; 4910 4911 public Set<K> keySet() { 4912 if (keySet==null) 4913 keySet = singleton(k); 4914 return keySet; 4915 } 4916 4917 public Set<Map.Entry<K,V>> entrySet() { 4918 if (entrySet==null) 4919 entrySet = Collections.<Map.Entry<K,V>>singleton( 4920 new SimpleImmutableEntry<>(k, v)); 4921 return entrySet; 4922 } 4923 4924 public Collection<V> values() { 4925 if (values==null) 4926 values = singleton(v); 4927 return values; 4928 } 4929 4930 // Override default methods in Map 4931 @Override 4932 public V getOrDefault(Object key, V defaultValue) { 4933 return eq(key, k) ? v : defaultValue; 4934 } 4935 4936 @Override 4937 public void forEach(BiConsumer<? super K, ? super V> action) { 4938 action.accept(k, v); 4939 } 4940 4941 @Override 4942 public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) { 4943 throw new UnsupportedOperationException(); 4944 } 4945 4946 @Override 4947 public V putIfAbsent(K key, V value) { 4948 throw new UnsupportedOperationException(); 4949 } 4950 4951 @Override 4952 public boolean remove(Object key, Object value) { 4953 throw new UnsupportedOperationException(); 4954 } 4955 4956 @Override 4957 public boolean replace(K key, V oldValue, V newValue) { 4958 throw new UnsupportedOperationException(); 4959 } 4960 4961 @Override 4962 public V replace(K key, V value) { 4963 throw new UnsupportedOperationException(); 4964 } 4965 4966 @Override 4967 public V computeIfAbsent(K key, 4968 Function<? super K, ? extends V> mappingFunction) { 4969 throw new UnsupportedOperationException(); 4970 } 4971 4972 @Override 4973 public V computeIfPresent(K key, 4974 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4975 throw new UnsupportedOperationException(); 4976 } 4977 4978 @Override 4979 public V compute(K key, 4980 BiFunction<? super K, ? super V, ? extends V> remappingFunction) { 4981 throw new UnsupportedOperationException(); 4982 } 4983 4984 @Override 4985 public V merge(K key, V value, 4986 BiFunction<? super V, ? super V, ? extends V> remappingFunction) { 4987 throw new UnsupportedOperationException(); 4988 } 4989 } 4990 4991 // Miscellaneous 4992 4993 /** 4994 * Returns an immutable list consisting of <tt>n</tt> copies of the 4995 * specified object. The newly allocated data object is tiny (it contains 4996 * a single reference to the data object). This method is useful in 4997 * combination with the <tt>List.addAll</tt> method to grow lists. 4998 * The returned list is serializable. 4999 * 5000 * @param <T> the class of the object to copy and of the objects 5001 * in the returned list. 5002 * @param n the number of elements in the returned list. 5003 * @param o the element to appear repeatedly in the returned list. 5004 * @return an immutable list consisting of <tt>n</tt> copies of the 5005 * specified object. 5006 * @throws IllegalArgumentException if {@code n < 0} 5007 * @see List#addAll(Collection) 5008 * @see List#addAll(int, Collection) 5009 */ 5010 public static <T> List<T> nCopies(int n, T o) { 5011 if (n < 0) 5012 throw new IllegalArgumentException("List length = " + n); 5013 return new CopiesList<>(n, o); 5014 } 5015 5016 /** 5017 * @serial include 5018 */ 5019 private static class CopiesList<E> 5020 extends AbstractList<E> 5021 implements RandomAccess, Serializable 5022 { 5023 private static final long serialVersionUID = 2739099268398711800L; 5024 5025 final int n; 5026 final E element; 5027 5028 CopiesList(int n, E e) { 5029 assert n >= 0; 5030 this.n = n; 5031 element = e; 5032 } 5033 5034 public int size() { 5035 return n; 5036 } 5037 5038 public boolean contains(Object obj) { 5039 return n != 0 && eq(obj, element); 5040 } 5041 5042 public int indexOf(Object o) { 5043 return contains(o) ? 0 : -1; 5044 } 5045 5046 public int lastIndexOf(Object o) { 5047 return contains(o) ? n - 1 : -1; 5048 } 5049 5050 public E get(int index) { 5051 if (index < 0 || index >= n) 5052 throw new IndexOutOfBoundsException("Index: "+index+ 5053 ", Size: "+n); 5054 return element; 5055 } 5056 5057 public Object[] toArray() { 5058 final Object[] a = new Object[n]; 5059 if (element != null) 5060 Arrays.fill(a, 0, n, element); 5061 return a; 5062 } 5063 5064 @SuppressWarnings("unchecked") 5065 public <T> T[] toArray(T[] a) { 5066 final int n = this.n; 5067 if (a.length < n) { 5068 a = (T[])java.lang.reflect.Array 5069 .newInstance(a.getClass().getComponentType(), n); 5070 if (element != null) 5071 Arrays.fill(a, 0, n, element); 5072 } else { 5073 Arrays.fill(a, 0, n, element); 5074 if (a.length > n) 5075 a[n] = null; 5076 } 5077 return a; 5078 } 5079 5080 public List<E> subList(int fromIndex, int toIndex) { 5081 if (fromIndex < 0) 5082 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); 5083 if (toIndex > n) 5084 throw new IndexOutOfBoundsException("toIndex = " + toIndex); 5085 if (fromIndex > toIndex) 5086 throw new IllegalArgumentException("fromIndex(" + fromIndex + 5087 ") > toIndex(" + toIndex + ")"); 5088 return new CopiesList<>(toIndex - fromIndex, element); 5089 } 5090 5091 // Override default methods in Collection 5092 @Override 5093 public Stream<E> stream() { 5094 return IntStream.range(0, n).mapToObj(i -> element); 5095 } 5096 5097 @Override 5098 public Stream<E> parallelStream() { 5099 return IntStream.range(0, n).parallel().mapToObj(i -> element); 5100 } 5101 5102 @Override 5103 public Spliterator<E> spliterator() { 5104 return stream().spliterator(); 5105 } 5106 } 5107 5108 /** 5109 * Returns a comparator that imposes the reverse of the <em>natural 5110 * ordering</em> on a collection of objects that implement the 5111 * {@code Comparable} interface. (The natural ordering is the ordering 5112 * imposed by the objects' own {@code compareTo} method.) This enables a 5113 * simple idiom for sorting (or maintaining) collections (or arrays) of 5114 * objects that implement the {@code Comparable} interface in 5115 * reverse-natural-order. For example, suppose {@code a} is an array of 5116 * strings. Then: <pre> 5117 * Arrays.sort(a, Collections.reverseOrder()); 5118 * </pre> sorts the array in reverse-lexicographic (alphabetical) order.<p> 5119 * 5120 * The returned comparator is serializable. 5121 * 5122 * @param <T> the class of the objects compared by the comparator 5123 * @return A comparator that imposes the reverse of the <i>natural 5124 * ordering</i> on a collection of objects that implement 5125 * the <tt>Comparable</tt> interface. 5126 * @see Comparable 5127 */ 5128 @SuppressWarnings("unchecked") 5129 public static <T> Comparator<T> reverseOrder() { 5130 return (Comparator<T>) ReverseComparator.REVERSE_ORDER; 5131 } 5132 5133 /** 5134 * @serial include 5135 */ 5136 private static class ReverseComparator 5137 implements Comparator<Comparable<Object>>, Serializable { 5138 5139 private static final long serialVersionUID = 7207038068494060240L; 5140 5141 static final ReverseComparator REVERSE_ORDER 5142 = new ReverseComparator(); 5143 5144 public int compare(Comparable<Object> c1, Comparable<Object> c2) { 5145 return c2.compareTo(c1); 5146 } 5147 5148 private Object readResolve() { return Collections.reverseOrder(); } 5149 5150 @Override 5151 public Comparator<Comparable<Object>> reversed() { 5152 return Comparator.naturalOrder(); 5153 } 5154 } 5155 5156 /** 5157 * Returns a comparator that imposes the reverse ordering of the specified 5158 * comparator. If the specified comparator is {@code null}, this method is 5159 * equivalent to {@link #reverseOrder()} (in other words, it returns a 5160 * comparator that imposes the reverse of the <em>natural ordering</em> on 5161 * a collection of objects that implement the Comparable interface). 5162 * 5163 * <p>The returned comparator is serializable (assuming the specified 5164 * comparator is also serializable or {@code null}). 5165 * 5166 * @param <T> the class of the objects compared by the comparator 5167 * @param cmp a comparator who's ordering is to be reversed by the returned 5168 * comparator or {@code null} 5169 * @return A comparator that imposes the reverse ordering of the 5170 * specified comparator. 5171 * @since 1.5 5172 */ 5173 public static <T> Comparator<T> reverseOrder(Comparator<T> cmp) { 5174 if (cmp == null) 5175 return reverseOrder(); 5176 5177 if (cmp instanceof ReverseComparator2) 5178 return ((ReverseComparator2<T>)cmp).cmp; 5179 5180 return new ReverseComparator2<>(cmp); 5181 } 5182 5183 /** 5184 * @serial include 5185 */ 5186 private static class ReverseComparator2<T> implements Comparator<T>, 5187 Serializable 5188 { 5189 private static final long serialVersionUID = 4374092139857L; 5190 5191 /** 5192 * The comparator specified in the static factory. This will never 5193 * be null, as the static factory returns a ReverseComparator 5194 * instance if its argument is null. 5195 * 5196 * @serial 5197 */ 5198 final Comparator<T> cmp; 5199 5200 ReverseComparator2(Comparator<T> cmp) { 5201 assert cmp != null; 5202 this.cmp = cmp; 5203 } 5204 5205 public int compare(T t1, T t2) { 5206 return cmp.compare(t2, t1); 5207 } 5208 5209 public boolean equals(Object o) { 5210 return (o == this) || 5211 (o instanceof ReverseComparator2 && 5212 cmp.equals(((ReverseComparator2)o).cmp)); 5213 } 5214 5215 public int hashCode() { 5216 return cmp.hashCode() ^ Integer.MIN_VALUE; 5217 } 5218 5219 @Override 5220 public Comparator<T> reversed() { 5221 return cmp; 5222 } 5223 } 5224 5225 /** 5226 * Returns an enumeration over the specified collection. This provides 5227 * interoperability with legacy APIs that require an enumeration 5228 * as input. 5229 * 5230 * @param <T> the class of the objects in the collection 5231 * @param c the collection for which an enumeration is to be returned. 5232 * @return an enumeration over the specified collection. 5233 * @see Enumeration 5234 */ 5235 public static <T> Enumeration<T> enumeration(final Collection<T> c) { 5236 return new Enumeration<T>() { 5237 private final Iterator<T> i = c.iterator(); 5238 5239 public boolean hasMoreElements() { 5240 return i.hasNext(); 5241 } 5242 5243 public T nextElement() { 5244 return i.next(); 5245 } 5246 }; 5247 } 5248 5249 /** 5250 * Returns an array list containing the elements returned by the 5251 * specified enumeration in the order they are returned by the 5252 * enumeration. This method provides interoperability between 5253 * legacy APIs that return enumerations and new APIs that require 5254 * collections. 5255 * 5256 * @param <T> the class of the objects returned by the enumeration 5257 * @param e enumeration providing elements for the returned 5258 * array list 5259 * @return an array list containing the elements returned 5260 * by the specified enumeration. 5261 * @since 1.4 5262 * @see Enumeration 5263 * @see ArrayList 5264 */ 5265 public static <T> ArrayList<T> list(Enumeration<T> e) { 5266 ArrayList<T> l = new ArrayList<>(); 5267 while (e.hasMoreElements()) 5268 l.add(e.nextElement()); 5269 return l; 5270 } 5271 5272 /** 5273 * Returns true if the specified arguments are equal, or both null. 5274 * 5275 * NB: Do not replace with Object.equals until JDK-8015417 is resolved. 5276 */ 5277 static boolean eq(Object o1, Object o2) { 5278 return o1==null ? o2==null : o1.equals(o2); 5279 } 5280 5281 /** 5282 * Returns the number of elements in the specified collection equal to the 5283 * specified object. More formally, returns the number of elements 5284 * <tt>e</tt> in the collection such that 5285 * <tt>(o == null ? e == null : o.equals(e))</tt>. 5286 * 5287 * @param c the collection in which to determine the frequency 5288 * of <tt>o</tt> 5289 * @param o the object whose frequency is to be determined 5290 * @return the number of elements in {@code c} equal to {@code o} 5291 * @throws NullPointerException if <tt>c</tt> is null 5292 * @since 1.5 5293 */ 5294 public static int frequency(Collection<?> c, Object o) { 5295 int result = 0; 5296 if (o == null) { 5297 for (Object e : c) 5298 if (e == null) 5299 result++; 5300 } else { 5301 for (Object e : c) 5302 if (o.equals(e)) 5303 result++; 5304 } 5305 return result; 5306 } 5307 5308 /** 5309 * Returns {@code true} if the two specified collections have no 5310 * elements in common. 5311 * 5312 * <p>Care must be exercised if this method is used on collections that 5313 * do not comply with the general contract for {@code Collection}. 5314 * Implementations may elect to iterate over either collection and test 5315 * for containment in the other collection (or to perform any equivalent 5316 * computation). If either collection uses a nonstandard equality test 5317 * (as does a {@link SortedSet} whose ordering is not <em>compatible with 5318 * equals</em>, or the key set of an {@link IdentityHashMap}), both 5319 * collections must use the same nonstandard equality test, or the 5320 * result of this method is undefined. 5321 * 5322 * <p>Care must also be exercised when using collections that have 5323 * restrictions on the elements that they may contain. Collection 5324 * implementations are allowed to throw exceptions for any operation 5325 * involving elements they deem ineligible. For absolute safety the 5326 * specified collections should contain only elements which are 5327 * eligible elements for both collections. 5328 * 5329 * <p>Note that it is permissible to pass the same collection in both 5330 * parameters, in which case the method will return {@code true} if and 5331 * only if the collection is empty. 5332 * 5333 * @param c1 a collection 5334 * @param c2 a collection 5335 * @return {@code true} if the two specified collections have no 5336 * elements in common. 5337 * @throws NullPointerException if either collection is {@code null}. 5338 * @throws NullPointerException if one collection contains a {@code null} 5339 * element and {@code null} is not an eligible element for the other collection. 5340 * (<a href="Collection.html#optional-restrictions">optional</a>) 5341 * @throws ClassCastException if one collection contains an element that is 5342 * of a type which is ineligible for the other collection. 5343 * (<a href="Collection.html#optional-restrictions">optional</a>) 5344 * @since 1.5 5345 */ 5346 public static boolean disjoint(Collection<?> c1, Collection<?> c2) { 5347 // The collection to be used for contains(). Preference is given to 5348 // the collection who's contains() has lower O() complexity. 5349 Collection<?> contains = c2; 5350 // The collection to be iterated. If the collections' contains() impl 5351 // are of different O() complexity, the collection with slower 5352 // contains() will be used for iteration. For collections who's 5353 // contains() are of the same complexity then best performance is 5354 // achieved by iterating the smaller collection. 5355 Collection<?> iterate = c1; 5356 5357 // Performance optimization cases. The heuristics: 5358 // 1. Generally iterate over c1. 5359 // 2. If c1 is a Set then iterate over c2. 5360 // 3. If either collection is empty then result is always true. 5361 // 4. Iterate over the smaller Collection. 5362 if (c1 instanceof Set) { 5363 // Use c1 for contains as a Set's contains() is expected to perform 5364 // better than O(N/2) 5365 iterate = c2; 5366 contains = c1; 5367 } else if (!(c2 instanceof Set)) { 5368 // Both are mere Collections. Iterate over smaller collection. 5369 // Example: If c1 contains 3 elements and c2 contains 50 elements and 5370 // assuming contains() requires ceiling(N/2) comparisons then 5371 // checking for all c1 elements in c2 would require 75 comparisons 5372 // (3 * ceiling(50/2)) vs. checking all c2 elements in c1 requiring 5373 // 100 comparisons (50 * ceiling(3/2)). 5374 int c1size = c1.size(); 5375 int c2size = c2.size(); 5376 if (c1size == 0 || c2size == 0) { 5377 // At least one collection is empty. Nothing will match. 5378 return true; 5379 } 5380 5381 if (c1size > c2size) { 5382 iterate = c2; 5383 contains = c1; 5384 } 5385 } 5386 5387 for (Object e : iterate) { 5388 if (contains.contains(e)) { 5389 // Found a common element. Collections are not disjoint. 5390 return false; 5391 } 5392 } 5393 5394 // No common elements were found. 5395 return true; 5396 } 5397 5398 /** 5399 * Adds all of the specified elements to the specified collection. 5400 * Elements to be added may be specified individually or as an array. 5401 * The behavior of this convenience method is identical to that of 5402 * <tt>c.addAll(Arrays.asList(elements))</tt>, but this method is likely 5403 * to run significantly faster under most implementations. 5404 * 5405 * <p>When elements are specified individually, this method provides a 5406 * convenient way to add a few elements to an existing collection: 5407 * <pre> 5408 * Collections.addAll(flavors, "Peaches 'n Plutonium", "Rocky Racoon"); 5409 * </pre> 5410 * 5411 * @param <T> the class of the elements to add and of the collection 5412 * @param c the collection into which <tt>elements</tt> are to be inserted 5413 * @param elements the elements to insert into <tt>c</tt> 5414 * @return <tt>true</tt> if the collection changed as a result of the call 5415 * @throws UnsupportedOperationException if <tt>c</tt> does not support 5416 * the <tt>add</tt> operation 5417 * @throws NullPointerException if <tt>elements</tt> contains one or more 5418 * null values and <tt>c</tt> does not permit null elements, or 5419 * if <tt>c</tt> or <tt>elements</tt> are <tt>null</tt> 5420 * @throws IllegalArgumentException if some property of a value in 5421 * <tt>elements</tt> prevents it from being added to <tt>c</tt> 5422 * @see Collection#addAll(Collection) 5423 * @since 1.5 5424 */ 5425 @SafeVarargs 5426 public static <T> boolean addAll(Collection<? super T> c, T... elements) { 5427 boolean result = false; 5428 for (T element : elements) 5429 result |= c.add(element); 5430 return result; 5431 } 5432 5433 /** 5434 * Returns a set backed by the specified map. The resulting set displays 5435 * the same ordering, concurrency, and performance characteristics as the 5436 * backing map. In essence, this factory method provides a {@link Set} 5437 * implementation corresponding to any {@link Map} implementation. There 5438 * is no need to use this method on a {@link Map} implementation that 5439 * already has a corresponding {@link Set} implementation (such as {@link 5440 * HashMap} or {@link TreeMap}). 5441 * 5442 * <p>Each method invocation on the set returned by this method results in 5443 * exactly one method invocation on the backing map or its <tt>keySet</tt> 5444 * view, with one exception. The <tt>addAll</tt> method is implemented 5445 * as a sequence of <tt>put</tt> invocations on the backing map. 5446 * 5447 * <p>The specified map must be empty at the time this method is invoked, 5448 * and should not be accessed directly after this method returns. These 5449 * conditions are ensured if the map is created empty, passed directly 5450 * to this method, and no reference to the map is retained, as illustrated 5451 * in the following code fragment: 5452 * <pre> 5453 * Set<Object> weakHashSet = Collections.newSetFromMap( 5454 * new WeakHashMap<Object, Boolean>()); 5455 * </pre> 5456 * 5457 * @param <E> the class of the map keys and of the objects in the 5458 * returned set 5459 * @param map the backing map 5460 * @return the set backed by the map 5461 * @throws IllegalArgumentException if <tt>map</tt> is not empty 5462 * @since 1.6 5463 */ 5464 public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) { 5465 return new SetFromMap<>(map); 5466 } 5467 5468 /** 5469 * @serial include 5470 */ 5471 private static class SetFromMap<E> extends AbstractSet<E> 5472 implements Set<E>, Serializable 5473 { 5474 private final Map<E, Boolean> m; // The backing map 5475 private transient Set<E> s; // Its keySet 5476 5477 SetFromMap(Map<E, Boolean> map) { 5478 if (!map.isEmpty()) 5479 throw new IllegalArgumentException("Map is non-empty"); 5480 m = map; 5481 s = map.keySet(); 5482 } 5483 5484 public void clear() { m.clear(); } 5485 public int size() { return m.size(); } 5486 public boolean isEmpty() { return m.isEmpty(); } 5487 public boolean contains(Object o) { return m.containsKey(o); } 5488 public boolean remove(Object o) { return m.remove(o) != null; } 5489 public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; } 5490 public Iterator<E> iterator() { return s.iterator(); } 5491 public Object[] toArray() { return s.toArray(); } 5492 public <T> T[] toArray(T[] a) { return s.toArray(a); } 5493 public String toString() { return s.toString(); } 5494 public int hashCode() { return s.hashCode(); } 5495 public boolean equals(Object o) { return o == this || s.equals(o); } 5496 public boolean containsAll(Collection<?> c) {return s.containsAll(c);} 5497 public boolean removeAll(Collection<?> c) {return s.removeAll(c);} 5498 public boolean retainAll(Collection<?> c) {return s.retainAll(c);} 5499 // addAll is the only inherited implementation 5500 5501 // Override default methods in Collection 5502 @Override 5503 public void forEach(Consumer<? super E> action) { 5504 s.forEach(action); 5505 } 5506 @Override 5507 public boolean removeIf(Predicate<? super E> filter) { 5508 return s.removeIf(filter); 5509 } 5510 5511 @Override 5512 public Spliterator<E> spliterator() {return s.spliterator();} 5513 @Override 5514 public Stream<E> stream() {return s.stream();} 5515 @Override 5516 public Stream<E> parallelStream() {return s.parallelStream();} 5517 5518 private static final long serialVersionUID = 2454657854757543876L; 5519 5520 private void readObject(java.io.ObjectInputStream stream) 5521 throws IOException, ClassNotFoundException 5522 { 5523 stream.defaultReadObject(); 5524 s = m.keySet(); 5525 } 5526 } 5527 5528 /** 5529 * Returns a view of a {@link Deque} as a Last-in-first-out (Lifo) 5530 * {@link Queue}. Method <tt>add</tt> is mapped to <tt>push</tt>, 5531 * <tt>remove</tt> is mapped to <tt>pop</tt> and so on. This 5532 * view can be useful when you would like to use a method 5533 * requiring a <tt>Queue</tt> but you need Lifo ordering. 5534 * 5535 * <p>Each method invocation on the queue returned by this method 5536 * results in exactly one method invocation on the backing deque, with 5537 * one exception. The {@link Queue#addAll addAll} method is 5538 * implemented as a sequence of {@link Deque#addFirst addFirst} 5539 * invocations on the backing deque. 5540 * 5541 * @param <T> the class of the objects in the deque 5542 * @param deque the deque 5543 * @return the queue 5544 * @since 1.6 5545 */ 5546 public static <T> Queue<T> asLifoQueue(Deque<T> deque) { 5547 return new AsLIFOQueue<>(deque); 5548 } 5549 5550 /** 5551 * @serial include 5552 */ 5553 static class AsLIFOQueue<E> extends AbstractQueue<E> 5554 implements Queue<E>, Serializable { 5555 private static final long serialVersionUID = 1802017725587941708L; 5556 private final Deque<E> q; 5557 AsLIFOQueue(Deque<E> q) { this.q = q; } 5558 public boolean add(E e) { q.addFirst(e); return true; } 5559 public boolean offer(E e) { return q.offerFirst(e); } 5560 public E poll() { return q.pollFirst(); } 5561 public E remove() { return q.removeFirst(); } 5562 public E peek() { return q.peekFirst(); } 5563 public E element() { return q.getFirst(); } 5564 public void clear() { q.clear(); } 5565 public int size() { return q.size(); } 5566 public boolean isEmpty() { return q.isEmpty(); } 5567 public boolean contains(Object o) { return q.contains(o); } 5568 public boolean remove(Object o) { return q.remove(o); } 5569 public Iterator<E> iterator() { return q.iterator(); } 5570 public Object[] toArray() { return q.toArray(); } 5571 public <T> T[] toArray(T[] a) { return q.toArray(a); } 5572 public String toString() { return q.toString(); } 5573 public boolean containsAll(Collection<?> c) {return q.containsAll(c);} 5574 public boolean removeAll(Collection<?> c) {return q.removeAll(c);} 5575 public boolean retainAll(Collection<?> c) {return q.retainAll(c);} 5576 // We use inherited addAll; forwarding addAll would be wrong 5577 5578 // Override default methods in Collection 5579 @Override 5580 public void forEach(Consumer<? super E> action) {q.forEach(action);} 5581 @Override 5582 public boolean removeIf(Predicate<? super E> filter) { 5583 return q.removeIf(filter); 5584 } 5585 @Override 5586 public Spliterator<E> spliterator() {return q.spliterator();} 5587 @Override 5588 public Stream<E> stream() {return q.stream();} 5589 @Override 5590 public Stream<E> parallelStream() {return q.parallelStream();} 5591 } 5592} 5593