1/* 2 * Copyright (C) 2008 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.google.common.primitives; 18 19import static com.google.common.base.Preconditions.checkArgument; 20import static com.google.common.base.Preconditions.checkElementIndex; 21import static com.google.common.base.Preconditions.checkNotNull; 22import static com.google.common.base.Preconditions.checkPositionIndexes; 23 24import com.google.common.annotations.GwtCompatible; 25 26import java.io.Serializable; 27import java.util.AbstractList; 28import java.util.Collection; 29import java.util.Collections; 30import java.util.Comparator; 31import java.util.List; 32import java.util.RandomAccess; 33 34/** 35 * Static utility methods pertaining to {@code char} primitives, that are not 36 * already found in either {@link Character} or {@link Arrays}. 37 * 38 * <p>All the operations in this class treat {@code char} values strictly 39 * numerically; they are neither Unicode-aware nor locale-dependent. 40 * 41 * @author Kevin Bourrillion 42 * @since 1.0 43 */ 44@GwtCompatible(emulated = true) 45public final class Chars { 46 private Chars() {} 47 48 /** 49 * The number of bytes required to represent a primitive {@code char} 50 * value. 51 */ 52 public static final int BYTES = Character.SIZE / Byte.SIZE; 53 54 /** 55 * Returns a hash code for {@code value}; equal to the result of invoking 56 * {@code ((Character) value).hashCode()}. 57 * 58 * @param value a primitive {@code char} value 59 * @return a hash code for the value 60 */ 61 public static int hashCode(char value) { 62 return value; 63 } 64 65 /** 66 * Returns the {@code char} value that is equal to {@code value}, if possible. 67 * 68 * @param value any value in the range of the {@code char} type 69 * @return the {@code char} value that equals {@code value} 70 * @throws IllegalArgumentException if {@code value} is greater than {@link 71 * Character#MAX_VALUE} or less than {@link Character#MIN_VALUE} 72 */ 73 public static char checkedCast(long value) { 74 char result = (char) value; 75 checkArgument(result == value, "Out of range: %s", value); 76 return result; 77 } 78 79 /** 80 * Returns the {@code char} nearest in value to {@code value}. 81 * 82 * @param value any {@code long} value 83 * @return the same value cast to {@code char} if it is in the range of the 84 * {@code char} type, {@link Character#MAX_VALUE} if it is too large, 85 * or {@link Character#MIN_VALUE} if it is too small 86 */ 87 public static char saturatedCast(long value) { 88 if (value > Character.MAX_VALUE) { 89 return Character.MAX_VALUE; 90 } 91 if (value < Character.MIN_VALUE) { 92 return Character.MIN_VALUE; 93 } 94 return (char) value; 95 } 96 97 /** 98 * Compares the two specified {@code char} values. The sign of the value 99 * returned is the same as that of {@code ((Character) a).compareTo(b)}. 100 * 101 * @param a the first {@code char} to compare 102 * @param b the second {@code char} to compare 103 * @return a negative value if {@code a} is less than {@code b}; a positive 104 * value if {@code a} is greater than {@code b}; or zero if they are equal 105 */ 106 public static int compare(char a, char b) { 107 return a - b; // safe due to restricted range 108 } 109 110 /** 111 * Returns {@code true} if {@code target} is present as an element anywhere in 112 * {@code array}. 113 * 114 * @param array an array of {@code char} values, possibly empty 115 * @param target a primitive {@code char} value 116 * @return {@code true} if {@code array[i] == target} for some value of {@code 117 * i} 118 */ 119 public static boolean contains(char[] array, char target) { 120 for (char value : array) { 121 if (value == target) { 122 return true; 123 } 124 } 125 return false; 126 } 127 128 /** 129 * Returns the index of the first appearance of the value {@code target} in 130 * {@code array}. 131 * 132 * @param array an array of {@code char} values, possibly empty 133 * @param target a primitive {@code char} value 134 * @return the least index {@code i} for which {@code array[i] == target}, or 135 * {@code -1} if no such index exists. 136 */ 137 public static int indexOf(char[] array, char target) { 138 return indexOf(array, target, 0, array.length); 139 } 140 141 // TODO(kevinb): consider making this public 142 private static int indexOf( 143 char[] array, char target, int start, int end) { 144 for (int i = start; i < end; i++) { 145 if (array[i] == target) { 146 return i; 147 } 148 } 149 return -1; 150 } 151 152 /** 153 * Returns the start position of the first occurrence of the specified {@code 154 * target} within {@code array}, or {@code -1} if there is no such occurrence. 155 * 156 * <p>More formally, returns the lowest index {@code i} such that {@code 157 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly 158 * the same elements as {@code target}. 159 * 160 * @param array the array to search for the sequence {@code target} 161 * @param target the array to search for as a sub-sequence of {@code array} 162 */ 163 public static int indexOf(char[] array, char[] target) { 164 checkNotNull(array, "array"); 165 checkNotNull(target, "target"); 166 if (target.length == 0) { 167 return 0; 168 } 169 170 outer: 171 for (int i = 0; i < array.length - target.length + 1; i++) { 172 for (int j = 0; j < target.length; j++) { 173 if (array[i + j] != target[j]) { 174 continue outer; 175 } 176 } 177 return i; 178 } 179 return -1; 180 } 181 182 /** 183 * Returns the index of the last appearance of the value {@code target} in 184 * {@code array}. 185 * 186 * @param array an array of {@code char} values, possibly empty 187 * @param target a primitive {@code char} value 188 * @return the greatest index {@code i} for which {@code array[i] == target}, 189 * or {@code -1} if no such index exists. 190 */ 191 public static int lastIndexOf(char[] array, char target) { 192 return lastIndexOf(array, target, 0, array.length); 193 } 194 195 // TODO(kevinb): consider making this public 196 private static int lastIndexOf( 197 char[] array, char target, int start, int end) { 198 for (int i = end - 1; i >= start; i--) { 199 if (array[i] == target) { 200 return i; 201 } 202 } 203 return -1; 204 } 205 206 /** 207 * Returns the least value present in {@code array}. 208 * 209 * @param array a <i>nonempty</i> array of {@code char} values 210 * @return the value present in {@code array} that is less than or equal to 211 * every other value in the array 212 * @throws IllegalArgumentException if {@code array} is empty 213 */ 214 public static char min(char... array) { 215 checkArgument(array.length > 0); 216 char min = array[0]; 217 for (int i = 1; i < array.length; i++) { 218 if (array[i] < min) { 219 min = array[i]; 220 } 221 } 222 return min; 223 } 224 225 /** 226 * Returns the greatest value present in {@code array}. 227 * 228 * @param array a <i>nonempty</i> array of {@code char} values 229 * @return the value present in {@code array} that is greater than or equal to 230 * every other value in the array 231 * @throws IllegalArgumentException if {@code array} is empty 232 */ 233 public static char max(char... array) { 234 checkArgument(array.length > 0); 235 char max = array[0]; 236 for (int i = 1; i < array.length; i++) { 237 if (array[i] > max) { 238 max = array[i]; 239 } 240 } 241 return max; 242 } 243 244 /** 245 * Returns the values from each provided array combined into a single array. 246 * For example, {@code concat(new char[] {a, b}, new char[] {}, new 247 * char[] {c}} returns the array {@code {a, b, c}}. 248 * 249 * @param arrays zero or more {@code char} arrays 250 * @return a single array containing all the values from the source arrays, in 251 * order 252 */ 253 public static char[] concat(char[]... arrays) { 254 int length = 0; 255 for (char[] array : arrays) { 256 length += array.length; 257 } 258 char[] result = new char[length]; 259 int pos = 0; 260 for (char[] array : arrays) { 261 System.arraycopy(array, 0, result, pos, array.length); 262 pos += array.length; 263 } 264 return result; 265 } 266 267 /** 268 * Returns an array containing the same values as {@code array}, but 269 * guaranteed to be of a specified minimum length. If {@code array} already 270 * has a length of at least {@code minLength}, it is returned directly. 271 * Otherwise, a new array of size {@code minLength + padding} is returned, 272 * containing the values of {@code array}, and zeroes in the remaining places. 273 * 274 * @param array the source array 275 * @param minLength the minimum length the returned array must guarantee 276 * @param padding an extra amount to "grow" the array by if growth is 277 * necessary 278 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is 279 * negative 280 * @return an array containing the values of {@code array}, with guaranteed 281 * minimum length {@code minLength} 282 */ 283 public static char[] ensureCapacity( 284 char[] array, int minLength, int padding) { 285 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 286 checkArgument(padding >= 0, "Invalid padding: %s", padding); 287 return (array.length < minLength) 288 ? copyOf(array, minLength + padding) 289 : array; 290 } 291 292 // Arrays.copyOf() requires Java 6 293 private static char[] copyOf(char[] original, int length) { 294 char[] copy = new char[length]; 295 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length)); 296 return copy; 297 } 298 299 /** 300 * Returns a string containing the supplied {@code char} values separated 301 * by {@code separator}. For example, {@code join("-", '1', '2', '3')} returns 302 * the string {@code "1-2-3"}. 303 * 304 * @param separator the text that should appear between consecutive values in 305 * the resulting string (but not at the start or end) 306 * @param array an array of {@code char} values, possibly empty 307 */ 308 public static String join(String separator, char... array) { 309 checkNotNull(separator); 310 int len = array.length; 311 if (len == 0) { 312 return ""; 313 } 314 315 StringBuilder builder 316 = new StringBuilder(len + separator.length() * (len - 1)); 317 builder.append(array[0]); 318 for (int i = 1; i < len; i++) { 319 builder.append(separator).append(array[i]); 320 } 321 return builder.toString(); 322 } 323 324 /** 325 * Returns a comparator that compares two {@code char} arrays 326 * lexicographically. That is, it compares, using {@link 327 * #compare(char, char)}), the first pair of values that follow any 328 * common prefix, or when one array is a prefix of the other, treats the 329 * shorter array as the lesser. For example, 330 * {@code [] < ['a'] < ['a', 'b'] < ['b']}. 331 * 332 * <p>The returned comparator is inconsistent with {@link 333 * Object#equals(Object)} (since arrays support only identity equality), but 334 * it is consistent with {@link Arrays#equals(char[], char[])}. 335 * 336 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> 337 * Lexicographical order article at Wikipedia</a> 338 * @since 2.0 339 */ 340 public static Comparator<char[]> lexicographicalComparator() { 341 return LexicographicalComparator.INSTANCE; 342 } 343 344 private enum LexicographicalComparator implements Comparator<char[]> { 345 INSTANCE; 346 347 @Override 348 public int compare(char[] left, char[] right) { 349 int minLength = Math.min(left.length, right.length); 350 for (int i = 0; i < minLength; i++) { 351 int result = Chars.compare(left[i], right[i]); 352 if (result != 0) { 353 return result; 354 } 355 } 356 return left.length - right.length; 357 } 358 } 359 360 /** 361 * Copies a collection of {@code Character} instances into a new array of 362 * primitive {@code char} values. 363 * 364 * <p>Elements are copied from the argument collection as if by {@code 365 * collection.toArray()}. Calling this method is as thread-safe as calling 366 * that method. 367 * 368 * @param collection a collection of {@code Character} objects 369 * @return an array containing the same values as {@code collection}, in the 370 * same order, converted to primitives 371 * @throws NullPointerException if {@code collection} or any of its elements 372 * is null 373 */ 374 public static char[] toArray(Collection<Character> collection) { 375 if (collection instanceof CharArrayAsList) { 376 return ((CharArrayAsList) collection).toCharArray(); 377 } 378 379 Object[] boxedArray = collection.toArray(); 380 int len = boxedArray.length; 381 char[] array = new char[len]; 382 for (int i = 0; i < len; i++) { 383 // checkNotNull for GWT (do not optimize) 384 array[i] = (Character) checkNotNull(boxedArray[i]); 385 } 386 return array; 387 } 388 389 /** 390 * Returns a fixed-size list backed by the specified array, similar to {@link 391 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, 392 * but any attempt to set a value to {@code null} will result in a {@link 393 * NullPointerException}. 394 * 395 * <p>The returned list maintains the values, but not the identities, of 396 * {@code Character} objects written to or read from it. For example, whether 397 * {@code list.get(0) == list.get(0)} is true for the returned list is 398 * unspecified. 399 * 400 * @param backingArray the array to back the list 401 * @return a list view of the array 402 */ 403 public static List<Character> asList(char... backingArray) { 404 if (backingArray.length == 0) { 405 return Collections.emptyList(); 406 } 407 return new CharArrayAsList(backingArray); 408 } 409 410 @GwtCompatible 411 private static class CharArrayAsList extends AbstractList<Character> 412 implements RandomAccess, Serializable { 413 final char[] array; 414 final int start; 415 final int end; 416 417 CharArrayAsList(char[] array) { 418 this(array, 0, array.length); 419 } 420 421 CharArrayAsList(char[] array, int start, int end) { 422 this.array = array; 423 this.start = start; 424 this.end = end; 425 } 426 427 @Override public int size() { 428 return end - start; 429 } 430 431 @Override public boolean isEmpty() { 432 return false; 433 } 434 435 @Override public Character get(int index) { 436 checkElementIndex(index, size()); 437 return array[start + index]; 438 } 439 440 @Override public boolean contains(Object target) { 441 // Overridden to prevent a ton of boxing 442 return (target instanceof Character) 443 && Chars.indexOf(array, (Character) target, start, end) != -1; 444 } 445 446 @Override public int indexOf(Object target) { 447 // Overridden to prevent a ton of boxing 448 if (target instanceof Character) { 449 int i = Chars.indexOf(array, (Character) target, start, end); 450 if (i >= 0) { 451 return i - start; 452 } 453 } 454 return -1; 455 } 456 457 @Override public int lastIndexOf(Object target) { 458 // Overridden to prevent a ton of boxing 459 if (target instanceof Character) { 460 int i = Chars.lastIndexOf(array, (Character) target, start, end); 461 if (i >= 0) { 462 return i - start; 463 } 464 } 465 return -1; 466 } 467 468 @Override public Character set(int index, Character element) { 469 checkElementIndex(index, size()); 470 char oldValue = array[start + index]; 471 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize) 472 return oldValue; 473 } 474 475 @Override public List<Character> subList(int fromIndex, int toIndex) { 476 int size = size(); 477 checkPositionIndexes(fromIndex, toIndex, size); 478 if (fromIndex == toIndex) { 479 return Collections.emptyList(); 480 } 481 return new CharArrayAsList(array, start + fromIndex, start + toIndex); 482 } 483 484 @Override public boolean equals(Object object) { 485 if (object == this) { 486 return true; 487 } 488 if (object instanceof CharArrayAsList) { 489 CharArrayAsList that = (CharArrayAsList) object; 490 int size = size(); 491 if (that.size() != size) { 492 return false; 493 } 494 for (int i = 0; i < size; i++) { 495 if (array[start + i] != that.array[that.start + i]) { 496 return false; 497 } 498 } 499 return true; 500 } 501 return super.equals(object); 502 } 503 504 @Override public int hashCode() { 505 int result = 1; 506 for (int i = start; i < end; i++) { 507 result = 31 * result + Chars.hashCode(array[i]); 508 } 509 return result; 510 } 511 512 @Override public String toString() { 513 StringBuilder builder = new StringBuilder(size() * 3); 514 builder.append('[').append(array[start]); 515 for (int i = start + 1; i < end; i++) { 516 builder.append(", ").append(array[i]); 517 } 518 return builder.append(']').toString(); 519 } 520 521 char[] toCharArray() { 522 // Arrays.copyOfRange() requires Java 6 523 int size = size(); 524 char[] result = new char[size]; 525 System.arraycopy(array, start, result, 0, size); 526 return result; 527 } 528 529 private static final long serialVersionUID = 0; 530 } 531} 532 533