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 17 package com.google.common.primitives; 18 19 import static com.google.common.base.Preconditions.checkArgument; 20 import static com.google.common.base.Preconditions.checkElementIndex; 21 import static com.google.common.base.Preconditions.checkNotNull; 22 import static com.google.common.base.Preconditions.checkPositionIndexes; 23 24 import com.google.common.annotations.GwtCompatible; 25 26 import java.io.Serializable; 27 import java.util.AbstractList; 28 import java.util.Collection; 29 import java.util.Collections; 30 import java.util.Comparator; 31 import java.util.List; 32 import 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 * <p>See the Guava User Guide article on <a href= 42 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained"> 43 * primitive utilities</a>. 44 * 45 * @author Kevin Bourrillion 46 * @since 1.0 47 */ 48 @GwtCompatible(emulated = true) 49 public final class Chars { 50 private Chars() {} 51 52 /** 53 * The number of bytes required to represent a primitive {@code char} 54 * value. 55 */ 56 public static final int BYTES = Character.SIZE / Byte.SIZE; 57 58 /** 59 * Returns a hash code for {@code value}; equal to the result of invoking 60 * {@code ((Character) value).hashCode()}. 61 * 62 * @param value a primitive {@code char} value 63 * @return a hash code for the value 64 */ 65 public static int hashCode(char value) { 66 return value; 67 } 68 69 /** 70 * Returns the {@code char} value that is equal to {@code value}, if possible. 71 * 72 * @param value any value in the range of the {@code char} type 73 * @return the {@code char} value that equals {@code value} 74 * @throws IllegalArgumentException if {@code value} is greater than {@link 75 * Character#MAX_VALUE} or less than {@link Character#MIN_VALUE} 76 */ 77 public static char checkedCast(long value) { 78 char result = (char) value; 79 if (result != value) { 80 // don't use checkArgument here, to avoid boxing 81 throw new IllegalArgumentException("Out of range: " + value); 82 } 83 return result; 84 } 85 86 /** 87 * Returns the {@code char} nearest in value to {@code value}. 88 * 89 * @param value any {@code long} value 90 * @return the same value cast to {@code char} if it is in the range of the 91 * {@code char} type, {@link Character#MAX_VALUE} if it is too large, 92 * or {@link Character#MIN_VALUE} if it is too small 93 */ 94 public static char saturatedCast(long value) { 95 if (value > Character.MAX_VALUE) { 96 return Character.MAX_VALUE; 97 } 98 if (value < Character.MIN_VALUE) { 99 return Character.MIN_VALUE; 100 } 101 return (char) value; 102 } 103 104 /** 105 * Compares the two specified {@code char} values. The sign of the value 106 * returned is the same as that of {@code ((Character) a).compareTo(b)}. 107 * 108 * <p><b>Note for Java 7 and later:</b> this method should be treated as 109 * deprecated; use the equivalent {@link Character#compare} method instead. 110 * 111 * @param a the first {@code char} to compare 112 * @param b the second {@code char} to compare 113 * @return a negative value if {@code a} is less than {@code b}; a positive 114 * value if {@code a} is greater than {@code b}; or zero if they are equal 115 */ 116 public static int compare(char a, char b) { 117 return a - b; // safe due to restricted range 118 } 119 120 /** 121 * Returns {@code true} if {@code target} is present as an element anywhere in 122 * {@code array}. 123 * 124 * @param array an array of {@code char} values, possibly empty 125 * @param target a primitive {@code char} value 126 * @return {@code true} if {@code array[i] == target} for some value of {@code 127 * i} 128 */ 129 public static boolean contains(char[] array, char target) { 130 for (char value : array) { 131 if (value == target) { 132 return true; 133 } 134 } 135 return false; 136 } 137 138 /** 139 * Returns the index of the first appearance of the value {@code target} in 140 * {@code array}. 141 * 142 * @param array an array of {@code char} values, possibly empty 143 * @param target a primitive {@code char} value 144 * @return the least index {@code i} for which {@code array[i] == target}, or 145 * {@code -1} if no such index exists. 146 */ 147 public static int indexOf(char[] array, char target) { 148 return indexOf(array, target, 0, array.length); 149 } 150 151 // TODO(kevinb): consider making this public 152 private static int indexOf( 153 char[] array, char target, int start, int end) { 154 for (int i = start; i < end; i++) { 155 if (array[i] == target) { 156 return i; 157 } 158 } 159 return -1; 160 } 161 162 /** 163 * Returns the start position of the first occurrence of the specified {@code 164 * target} within {@code array}, or {@code -1} if there is no such occurrence. 165 * 166 * <p>More formally, returns the lowest index {@code i} such that {@code 167 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly 168 * the same elements as {@code target}. 169 * 170 * @param array the array to search for the sequence {@code target} 171 * @param target the array to search for as a sub-sequence of {@code array} 172 */ 173 public static int indexOf(char[] array, char[] target) { 174 checkNotNull(array, "array"); 175 checkNotNull(target, "target"); 176 if (target.length == 0) { 177 return 0; 178 } 179 180 outer: 181 for (int i = 0; i < array.length - target.length + 1; i++) { 182 for (int j = 0; j < target.length; j++) { 183 if (array[i + j] != target[j]) { 184 continue outer; 185 } 186 } 187 return i; 188 } 189 return -1; 190 } 191 192 /** 193 * Returns the index of the last appearance of the value {@code target} in 194 * {@code array}. 195 * 196 * @param array an array of {@code char} values, possibly empty 197 * @param target a primitive {@code char} value 198 * @return the greatest index {@code i} for which {@code array[i] == target}, 199 * or {@code -1} if no such index exists. 200 */ 201 public static int lastIndexOf(char[] array, char target) { 202 return lastIndexOf(array, target, 0, array.length); 203 } 204 205 // TODO(kevinb): consider making this public 206 private static int lastIndexOf( 207 char[] array, char target, int start, int end) { 208 for (int i = end - 1; i >= start; i--) { 209 if (array[i] == target) { 210 return i; 211 } 212 } 213 return -1; 214 } 215 216 /** 217 * Returns the least value present in {@code array}. 218 * 219 * @param array a <i>nonempty</i> array of {@code char} values 220 * @return the value present in {@code array} that is less than or equal to 221 * every other value in the array 222 * @throws IllegalArgumentException if {@code array} is empty 223 */ 224 public static char min(char... array) { 225 checkArgument(array.length > 0); 226 char min = array[0]; 227 for (int i = 1; i < array.length; i++) { 228 if (array[i] < min) { 229 min = array[i]; 230 } 231 } 232 return min; 233 } 234 235 /** 236 * Returns the greatest value present in {@code array}. 237 * 238 * @param array a <i>nonempty</i> array of {@code char} values 239 * @return the value present in {@code array} that is greater than or equal to 240 * every other value in the array 241 * @throws IllegalArgumentException if {@code array} is empty 242 */ 243 public static char max(char... array) { 244 checkArgument(array.length > 0); 245 char max = array[0]; 246 for (int i = 1; i < array.length; i++) { 247 if (array[i] > max) { 248 max = array[i]; 249 } 250 } 251 return max; 252 } 253 254 /** 255 * Returns the values from each provided array combined into a single array. 256 * For example, {@code concat(new char[] {a, b}, new char[] {}, new 257 * char[] {c}} returns the array {@code {a, b, c}}. 258 * 259 * @param arrays zero or more {@code char} arrays 260 * @return a single array containing all the values from the source arrays, in 261 * order 262 */ 263 public static char[] concat(char[]... arrays) { 264 int length = 0; 265 for (char[] array : arrays) { 266 length += array.length; 267 } 268 char[] result = new char[length]; 269 int pos = 0; 270 for (char[] array : arrays) { 271 System.arraycopy(array, 0, result, pos, array.length); 272 pos += array.length; 273 } 274 return result; 275 } 276 277 /** 278 * Returns an array containing the same values as {@code array}, but 279 * guaranteed to be of a specified minimum length. If {@code array} already 280 * has a length of at least {@code minLength}, it is returned directly. 281 * Otherwise, a new array of size {@code minLength + padding} is returned, 282 * containing the values of {@code array}, and zeroes in the remaining places. 283 * 284 * @param array the source array 285 * @param minLength the minimum length the returned array must guarantee 286 * @param padding an extra amount to "grow" the array by if growth is 287 * necessary 288 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is 289 * negative 290 * @return an array containing the values of {@code array}, with guaranteed 291 * minimum length {@code minLength} 292 */ 293 public static char[] ensureCapacity( 294 char[] array, int minLength, int padding) { 295 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 296 checkArgument(padding >= 0, "Invalid padding: %s", padding); 297 return (array.length < minLength) 298 ? copyOf(array, minLength + padding) 299 : array; 300 } 301 302 // Arrays.copyOf() requires Java 6 303 private static char[] copyOf(char[] original, int length) { 304 char[] copy = new char[length]; 305 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length)); 306 return copy; 307 } 308 309 /** 310 * Returns a string containing the supplied {@code char} values separated 311 * by {@code separator}. For example, {@code join("-", '1', '2', '3')} returns 312 * the string {@code "1-2-3"}. 313 * 314 * @param separator the text that should appear between consecutive values in 315 * the resulting string (but not at the start or end) 316 * @param array an array of {@code char} values, possibly empty 317 */ 318 public static String join(String separator, char... array) { 319 checkNotNull(separator); 320 int len = array.length; 321 if (len == 0) { 322 return ""; 323 } 324 325 StringBuilder builder 326 = new StringBuilder(len + separator.length() * (len - 1)); 327 builder.append(array[0]); 328 for (int i = 1; i < len; i++) { 329 builder.append(separator).append(array[i]); 330 } 331 return builder.toString(); 332 } 333 334 /** 335 * Returns a comparator that compares two {@code char} arrays 336 * lexicographically. That is, it compares, using {@link 337 * #compare(char, char)}), the first pair of values that follow any 338 * common prefix, or when one array is a prefix of the other, treats the 339 * shorter array as the lesser. For example, 340 * {@code [] < ['a'] < ['a', 'b'] < ['b']}. 341 * 342 * <p>The returned comparator is inconsistent with {@link 343 * Object#equals(Object)} (since arrays support only identity equality), but 344 * it is consistent with {@link Arrays#equals(char[], char[])}. 345 * 346 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order"> 347 * Lexicographical order article at Wikipedia</a> 348 * @since 2.0 349 */ 350 public static Comparator<char[]> lexicographicalComparator() { 351 return LexicographicalComparator.INSTANCE; 352 } 353 354 private enum LexicographicalComparator implements Comparator<char[]> { 355 INSTANCE; 356 357 @Override 358 public int compare(char[] left, char[] right) { 359 int minLength = Math.min(left.length, right.length); 360 for (int i = 0; i < minLength; i++) { 361 int result = Chars.compare(left[i], right[i]); 362 if (result != 0) { 363 return result; 364 } 365 } 366 return left.length - right.length; 367 } 368 } 369 370 /** 371 * Copies a collection of {@code Character} instances into a new array of 372 * primitive {@code char} values. 373 * 374 * <p>Elements are copied from the argument collection as if by {@code 375 * collection.toArray()}. Calling this method is as thread-safe as calling 376 * that method. 377 * 378 * @param collection a collection of {@code Character} objects 379 * @return an array containing the same values as {@code collection}, in the 380 * same order, converted to primitives 381 * @throws NullPointerException if {@code collection} or any of its elements 382 * is null 383 */ 384 public static char[] toArray(Collection<Character> collection) { 385 if (collection instanceof CharArrayAsList) { 386 return ((CharArrayAsList) collection).toCharArray(); 387 } 388 389 Object[] boxedArray = collection.toArray(); 390 int len = boxedArray.length; 391 char[] array = new char[len]; 392 for (int i = 0; i < len; i++) { 393 // checkNotNull for GWT (do not optimize) 394 array[i] = (Character) checkNotNull(boxedArray[i]); 395 } 396 return array; 397 } 398 399 /** 400 * Returns a fixed-size list backed by the specified array, similar to {@link 401 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, 402 * but any attempt to set a value to {@code null} will result in a {@link 403 * NullPointerException}. 404 * 405 * <p>The returned list maintains the values, but not the identities, of 406 * {@code Character} objects written to or read from it. For example, whether 407 * {@code list.get(0) == list.get(0)} is true for the returned list is 408 * unspecified. 409 * 410 * @param backingArray the array to back the list 411 * @return a list view of the array 412 */ 413 public static List<Character> asList(char... backingArray) { 414 if (backingArray.length == 0) { 415 return Collections.emptyList(); 416 } 417 return new CharArrayAsList(backingArray); 418 } 419 420 @GwtCompatible 421 private static class CharArrayAsList extends AbstractList<Character> 422 implements RandomAccess, Serializable { 423 final char[] array; 424 final int start; 425 final int end; 426 427 CharArrayAsList(char[] array) { 428 this(array, 0, array.length); 429 } 430 431 CharArrayAsList(char[] array, int start, int end) { 432 this.array = array; 433 this.start = start; 434 this.end = end; 435 } 436 437 @Override public int size() { 438 return end - start; 439 } 440 441 @Override public boolean isEmpty() { 442 return false; 443 } 444 445 @Override public Character get(int index) { 446 checkElementIndex(index, size()); 447 return array[start + index]; 448 } 449 450 @Override public boolean contains(Object target) { 451 // Overridden to prevent a ton of boxing 452 return (target instanceof Character) 453 && Chars.indexOf(array, (Character) target, start, end) != -1; 454 } 455 456 @Override public int indexOf(Object target) { 457 // Overridden to prevent a ton of boxing 458 if (target instanceof Character) { 459 int i = Chars.indexOf(array, (Character) target, start, end); 460 if (i >= 0) { 461 return i - start; 462 } 463 } 464 return -1; 465 } 466 467 @Override public int lastIndexOf(Object target) { 468 // Overridden to prevent a ton of boxing 469 if (target instanceof Character) { 470 int i = Chars.lastIndexOf(array, (Character) target, start, end); 471 if (i >= 0) { 472 return i - start; 473 } 474 } 475 return -1; 476 } 477 478 @Override public Character set(int index, Character element) { 479 checkElementIndex(index, size()); 480 char oldValue = array[start + index]; 481 // checkNotNull for GWT (do not optimize) 482 array[start + index] = checkNotNull(element); 483 return oldValue; 484 } 485 486 @Override public List<Character> subList(int fromIndex, int toIndex) { 487 int size = size(); 488 checkPositionIndexes(fromIndex, toIndex, size); 489 if (fromIndex == toIndex) { 490 return Collections.emptyList(); 491 } 492 return new CharArrayAsList(array, start + fromIndex, start + toIndex); 493 } 494 495 @Override public boolean equals(Object object) { 496 if (object == this) { 497 return true; 498 } 499 if (object instanceof CharArrayAsList) { 500 CharArrayAsList that = (CharArrayAsList) object; 501 int size = size(); 502 if (that.size() != size) { 503 return false; 504 } 505 for (int i = 0; i < size; i++) { 506 if (array[start + i] != that.array[that.start + i]) { 507 return false; 508 } 509 } 510 return true; 511 } 512 return super.equals(object); 513 } 514 515 @Override public int hashCode() { 516 int result = 1; 517 for (int i = start; i < end; i++) { 518 result = 31 * result + Chars.hashCode(array[i]); 519 } 520 return result; 521 } 522 523 @Override public String toString() { 524 StringBuilder builder = new StringBuilder(size() * 3); 525 builder.append('[').append(array[start]); 526 for (int i = start + 1; i < end; i++) { 527 builder.append(", ").append(array[i]); 528 } 529 return builder.append(']').toString(); 530 } 531 532 char[] toCharArray() { 533 // Arrays.copyOfRange() is not available under GWT 534 int size = size(); 535 char[] result = new char[size]; 536 System.arraycopy(array, start, result, 0, size); 537 return result; 538 } 539 540 private static final long serialVersionUID = 0; 541 } 542 } 543