001/* 002 * Copyright (C) 2008 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkElementIndex; 019import static com.google.common.base.Preconditions.checkNotNull; 020import static com.google.common.base.Preconditions.checkPositionIndexes; 021 022import com.google.common.annotations.Beta; 023import com.google.common.annotations.GwtCompatible; 024import com.google.common.annotations.GwtIncompatible; 025import java.io.Serializable; 026import java.util.AbstractList; 027import java.util.Arrays; 028import java.util.Collection; 029import java.util.Collections; 030import java.util.Comparator; 031import java.util.List; 032import java.util.RandomAccess; 033import javax.annotation.CheckForNull; 034 035/** 036 * Static utility methods pertaining to {@code char} primitives, that are not already found in 037 * either {@link Character} or {@link Arrays}. 038 * 039 * <p>All the operations in this class treat {@code char} values strictly numerically; they are 040 * neither Unicode-aware nor locale-dependent. 041 * 042 * <p>See the Guava User Guide article on <a 043 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 044 * 045 * @author Kevin Bourrillion 046 * @since 1.0 047 */ 048@GwtCompatible(emulated = true) 049@ElementTypesAreNonnullByDefault 050public final class Chars { 051 private Chars() {} 052 053 /** 054 * The number of bytes required to represent a primitive {@code char} value. 055 * 056 * <p><b>Java 8 users:</b> use {@link Character#BYTES} instead. 057 */ 058 public static final int BYTES = Character.SIZE / Byte.SIZE; 059 060 /** 061 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Character) 062 * value).hashCode()}. 063 * 064 * <p><b>Java 8 users:</b> use {@link Character#hashCode(char)} instead. 065 * 066 * @param value a primitive {@code char} value 067 * @return a hash code for the value 068 */ 069 public static int hashCode(char value) { 070 return value; 071 } 072 073 /** 074 * Returns the {@code char} value that is equal to {@code value}, if possible. 075 * 076 * @param value any value in the range of the {@code char} type 077 * @return the {@code char} value that equals {@code value} 078 * @throws IllegalArgumentException if {@code value} is greater than {@link Character#MAX_VALUE} 079 * or less than {@link Character#MIN_VALUE} 080 */ 081 public static char checkedCast(long value) { 082 char result = (char) value; 083 checkArgument(result == value, "Out of range: %s", value); 084 return result; 085 } 086 087 /** 088 * Returns the {@code char} nearest in value to {@code value}. 089 * 090 * @param value any {@code long} value 091 * @return the same value cast to {@code char} if it is in the range of the {@code char} type, 092 * {@link Character#MAX_VALUE} if it is too large, or {@link Character#MIN_VALUE} if it is too 093 * small 094 */ 095 public static char saturatedCast(long value) { 096 if (value > Character.MAX_VALUE) { 097 return Character.MAX_VALUE; 098 } 099 if (value < Character.MIN_VALUE) { 100 return Character.MIN_VALUE; 101 } 102 return (char) value; 103 } 104 105 /** 106 * Compares the two specified {@code char} values. The sign of the value returned is the same as 107 * that of {@code ((Character) a).compareTo(b)}. 108 * 109 * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the 110 * equivalent {@link Character#compare} method instead. 111 * 112 * @param a the first {@code char} to compare 113 * @param b the second {@code char} to compare 114 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 115 * greater than {@code b}; or zero if they are equal 116 */ 117 public static int compare(char a, char b) { 118 return a - b; // safe due to restricted range 119 } 120 121 /** 122 * Returns {@code true} if {@code target} is present as an element anywhere in {@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 i} 127 */ 128 public static boolean contains(char[] array, char target) { 129 for (char value : array) { 130 if (value == target) { 131 return true; 132 } 133 } 134 return false; 135 } 136 137 /** 138 * Returns the index of the first appearance of the value {@code target} in {@code array}. 139 * 140 * @param array an array of {@code char} values, possibly empty 141 * @param target a primitive {@code char} value 142 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 143 * such index exists. 144 */ 145 public static int indexOf(char[] array, char target) { 146 return indexOf(array, target, 0, array.length); 147 } 148 149 // TODO(kevinb): consider making this public 150 private static int indexOf(char[] array, char target, int start, int end) { 151 for (int i = start; i < end; i++) { 152 if (array[i] == target) { 153 return i; 154 } 155 } 156 return -1; 157 } 158 159 /** 160 * Returns the start position of the first occurrence of the specified {@code target} within 161 * {@code array}, or {@code -1} if there is no such occurrence. 162 * 163 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 164 * i, i + target.length)} contains exactly the same elements as {@code target}. 165 * 166 * @param array the array to search for the sequence {@code target} 167 * @param target the array to search for as a sub-sequence of {@code array} 168 */ 169 public static int indexOf(char[] array, char[] target) { 170 checkNotNull(array, "array"); 171 checkNotNull(target, "target"); 172 if (target.length == 0) { 173 return 0; 174 } 175 176 outer: 177 for (int i = 0; i < array.length - target.length + 1; i++) { 178 for (int j = 0; j < target.length; j++) { 179 if (array[i + j] != target[j]) { 180 continue outer; 181 } 182 } 183 return i; 184 } 185 return -1; 186 } 187 188 /** 189 * Returns the index of the last appearance of the value {@code target} in {@code array}. 190 * 191 * @param array an array of {@code char} values, possibly empty 192 * @param target a primitive {@code char} value 193 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 194 * such index exists. 195 */ 196 public static int lastIndexOf(char[] array, char target) { 197 return lastIndexOf(array, target, 0, array.length); 198 } 199 200 // TODO(kevinb): consider making this public 201 private static int lastIndexOf(char[] array, char target, int start, int end) { 202 for (int i = end - 1; i >= start; i--) { 203 if (array[i] == target) { 204 return i; 205 } 206 } 207 return -1; 208 } 209 210 /** 211 * Returns the least value present in {@code array}. 212 * 213 * @param array a <i>nonempty</i> array of {@code char} values 214 * @return the value present in {@code array} that is less than or equal to every other value in 215 * the array 216 * @throws IllegalArgumentException if {@code array} is empty 217 */ 218 public static char min(char... array) { 219 checkArgument(array.length > 0); 220 char min = array[0]; 221 for (int i = 1; i < array.length; i++) { 222 if (array[i] < min) { 223 min = array[i]; 224 } 225 } 226 return min; 227 } 228 229 /** 230 * Returns the greatest value present in {@code array}. 231 * 232 * @param array a <i>nonempty</i> array of {@code char} values 233 * @return the value present in {@code array} that is greater than or equal to every other value 234 * in the array 235 * @throws IllegalArgumentException if {@code array} is empty 236 */ 237 public static char max(char... array) { 238 checkArgument(array.length > 0); 239 char max = array[0]; 240 for (int i = 1; i < array.length; i++) { 241 if (array[i] > max) { 242 max = array[i]; 243 } 244 } 245 return max; 246 } 247 248 /** 249 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 250 * 251 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 252 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 253 * value} is greater than {@code max}, {@code max} is returned. 254 * 255 * @param value the {@code char} value to constrain 256 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 257 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 258 * @throws IllegalArgumentException if {@code min > max} 259 * @since 21.0 260 */ 261 @Beta 262 public static char constrainToRange(char value, char min, char max) { 263 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 264 return value < min ? min : value < max ? value : max; 265 } 266 267 /** 268 * Returns the values from each provided array combined into a single array. For example, {@code 269 * concat(new char[] {a, b}, new char[] {}, new char[] {c}} returns the array {@code {a, b, c}}. 270 * 271 * @param arrays zero or more {@code char} arrays 272 * @return a single array containing all the values from the source arrays, in order 273 */ 274 public static char[] concat(char[]... arrays) { 275 int length = 0; 276 for (char[] array : arrays) { 277 length += array.length; 278 } 279 char[] result = new char[length]; 280 int pos = 0; 281 for (char[] array : arrays) { 282 System.arraycopy(array, 0, result, pos, array.length); 283 pos += array.length; 284 } 285 return result; 286 } 287 288 /** 289 * Returns a big-endian representation of {@code value} in a 2-element byte array; equivalent to 290 * {@code ByteBuffer.allocate(2).putChar(value).array()}. For example, the input value {@code 291 * '\\u5432'} would yield the byte array {@code {0x54, 0x32}}. 292 * 293 * <p>If you need to convert and concatenate several values (possibly even of different types), 294 * use a shared {@link java.nio.ByteBuffer} instance, or use {@link 295 * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer. 296 */ 297 @GwtIncompatible // doesn't work 298 public static byte[] toByteArray(char value) { 299 return new byte[] {(byte) (value >> 8), (byte) value}; 300 } 301 302 /** 303 * Returns the {@code char} value whose big-endian representation is stored in the first 2 bytes 304 * of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getChar()}. For example, the 305 * input byte array {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}. 306 * 307 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more 308 * flexibility at little cost in readability. 309 * 310 * @throws IllegalArgumentException if {@code bytes} has fewer than 2 elements 311 */ 312 @GwtIncompatible // doesn't work 313 public static char fromByteArray(byte[] bytes) { 314 checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES); 315 return fromBytes(bytes[0], bytes[1]); 316 } 317 318 /** 319 * Returns the {@code char} value whose byte representation is the given 2 bytes, in big-endian 320 * order; equivalent to {@code Chars.fromByteArray(new byte[] {b1, b2})}. 321 * 322 * @since 7.0 323 */ 324 @GwtIncompatible // doesn't work 325 public static char fromBytes(byte b1, byte b2) { 326 return (char) ((b1 << 8) | (b2 & 0xFF)); 327 } 328 329 /** 330 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 331 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 332 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 333 * returned, containing the values of {@code array}, and zeroes in the remaining places. 334 * 335 * @param array the source array 336 * @param minLength the minimum length the returned array must guarantee 337 * @param padding an extra amount to "grow" the array by if growth is necessary 338 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 339 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 340 * minLength} 341 */ 342 public static char[] ensureCapacity(char[] array, int minLength, int padding) { 343 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 344 checkArgument(padding >= 0, "Invalid padding: %s", padding); 345 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 346 } 347 348 /** 349 * Returns a string containing the supplied {@code char} values separated by {@code separator}. 350 * For example, {@code join("-", '1', '2', '3')} returns the string {@code "1-2-3"}. 351 * 352 * @param separator the text that should appear between consecutive values in the resulting string 353 * (but not at the start or end) 354 * @param array an array of {@code char} values, possibly empty 355 */ 356 public static String join(String separator, char... array) { 357 checkNotNull(separator); 358 int len = array.length; 359 if (len == 0) { 360 return ""; 361 } 362 363 StringBuilder builder = new StringBuilder(len + separator.length() * (len - 1)); 364 builder.append(array[0]); 365 for (int i = 1; i < len; i++) { 366 builder.append(separator).append(array[i]); 367 } 368 return builder.toString(); 369 } 370 371 /** 372 * Returns a comparator that compares two {@code char} arrays <a 373 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>; not advisable 374 * for sorting user-visible strings as the ordering may not match the conventions of the user's 375 * locale. That is, it compares, using {@link #compare(char, char)}), the first pair of values 376 * that follow any common prefix, or when one array is a prefix of the other, treats the shorter 377 * array as the lesser. For example, {@code [] < ['a'] < ['a', 'b'] < ['b']}. 378 * 379 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 380 * support only identity equality), but it is consistent with {@link Arrays#equals(char[], 381 * char[])}. 382 * 383 * @since 2.0 384 */ 385 public static Comparator<char[]> lexicographicalComparator() { 386 return LexicographicalComparator.INSTANCE; 387 } 388 389 private enum LexicographicalComparator implements Comparator<char[]> { 390 INSTANCE; 391 392 @Override 393 public int compare(char[] left, char[] right) { 394 int minLength = Math.min(left.length, right.length); 395 for (int i = 0; i < minLength; i++) { 396 int result = Chars.compare(left[i], right[i]); 397 if (result != 0) { 398 return result; 399 } 400 } 401 return left.length - right.length; 402 } 403 404 @Override 405 public String toString() { 406 return "Chars.lexicographicalComparator()"; 407 } 408 } 409 410 /** 411 * Copies a collection of {@code Character} instances into a new array of primitive {@code char} 412 * values. 413 * 414 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 415 * Calling this method is as thread-safe as calling that method. 416 * 417 * @param collection a collection of {@code Character} objects 418 * @return an array containing the same values as {@code collection}, in the same order, converted 419 * to primitives 420 * @throws NullPointerException if {@code collection} or any of its elements is null 421 */ 422 public static char[] toArray(Collection<Character> collection) { 423 if (collection instanceof CharArrayAsList) { 424 return ((CharArrayAsList) collection).toCharArray(); 425 } 426 427 Object[] boxedArray = collection.toArray(); 428 int len = boxedArray.length; 429 char[] array = new char[len]; 430 for (int i = 0; i < len; i++) { 431 // checkNotNull for GWT (do not optimize) 432 array[i] = (Character) checkNotNull(boxedArray[i]); 433 } 434 return array; 435 } 436 437 /** 438 * Sorts the elements of {@code array} in descending order. 439 * 440 * @since 23.1 441 */ 442 public static void sortDescending(char[] array) { 443 checkNotNull(array); 444 sortDescending(array, 0, array.length); 445 } 446 447 /** 448 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 449 * exclusive in descending order. 450 * 451 * @since 23.1 452 */ 453 public static void sortDescending(char[] array, int fromIndex, int toIndex) { 454 checkNotNull(array); 455 checkPositionIndexes(fromIndex, toIndex, array.length); 456 Arrays.sort(array, fromIndex, toIndex); 457 reverse(array, fromIndex, toIndex); 458 } 459 460 /** 461 * Reverses the elements of {@code array}. This is equivalent to {@code 462 * Collections.reverse(Chars.asList(array))}, but is likely to be more efficient. 463 * 464 * @since 23.1 465 */ 466 public static void reverse(char[] array) { 467 checkNotNull(array); 468 reverse(array, 0, array.length); 469 } 470 471 /** 472 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 473 * exclusive. This is equivalent to {@code 474 * Collections.reverse(Chars.asList(array).subList(fromIndex, toIndex))}, but is likely to be more 475 * efficient. 476 * 477 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 478 * {@code toIndex > fromIndex} 479 * @since 23.1 480 */ 481 public static void reverse(char[] array, int fromIndex, int toIndex) { 482 checkNotNull(array); 483 checkPositionIndexes(fromIndex, toIndex, array.length); 484 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 485 char tmp = array[i]; 486 array[i] = array[j]; 487 array[j] = tmp; 488 } 489 } 490 491 /** 492 * Returns a fixed-size list backed by the specified array, similar to {@link 493 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 494 * set a value to {@code null} will result in a {@link NullPointerException}. 495 * 496 * <p>The returned list maintains the values, but not the identities, of {@code Character} objects 497 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 498 * the returned list is unspecified. 499 * 500 * @param backingArray the array to back the list 501 * @return a list view of the array 502 */ 503 public static List<Character> asList(char... backingArray) { 504 if (backingArray.length == 0) { 505 return Collections.emptyList(); 506 } 507 return new CharArrayAsList(backingArray); 508 } 509 510 @GwtCompatible 511 private static class CharArrayAsList extends AbstractList<Character> 512 implements RandomAccess, Serializable { 513 final char[] array; 514 final int start; 515 final int end; 516 517 CharArrayAsList(char[] array) { 518 this(array, 0, array.length); 519 } 520 521 CharArrayAsList(char[] array, int start, int end) { 522 this.array = array; 523 this.start = start; 524 this.end = end; 525 } 526 527 @Override 528 public int size() { 529 return end - start; 530 } 531 532 @Override 533 public boolean isEmpty() { 534 return false; 535 } 536 537 @Override 538 public Character get(int index) { 539 checkElementIndex(index, size()); 540 return array[start + index]; 541 } 542 543 @Override 544 public boolean contains(@CheckForNull Object target) { 545 // Overridden to prevent a ton of boxing 546 return (target instanceof Character) 547 && Chars.indexOf(array, (Character) target, start, end) != -1; 548 } 549 550 @Override 551 public int indexOf(@CheckForNull Object target) { 552 // Overridden to prevent a ton of boxing 553 if (target instanceof Character) { 554 int i = Chars.indexOf(array, (Character) target, start, end); 555 if (i >= 0) { 556 return i - start; 557 } 558 } 559 return -1; 560 } 561 562 @Override 563 public int lastIndexOf(@CheckForNull Object target) { 564 // Overridden to prevent a ton of boxing 565 if (target instanceof Character) { 566 int i = Chars.lastIndexOf(array, (Character) target, start, end); 567 if (i >= 0) { 568 return i - start; 569 } 570 } 571 return -1; 572 } 573 574 @Override 575 public Character set(int index, Character element) { 576 checkElementIndex(index, size()); 577 char oldValue = array[start + index]; 578 // checkNotNull for GWT (do not optimize) 579 array[start + index] = checkNotNull(element); 580 return oldValue; 581 } 582 583 @Override 584 public List<Character> subList(int fromIndex, int toIndex) { 585 int size = size(); 586 checkPositionIndexes(fromIndex, toIndex, size); 587 if (fromIndex == toIndex) { 588 return Collections.emptyList(); 589 } 590 return new CharArrayAsList(array, start + fromIndex, start + toIndex); 591 } 592 593 @Override 594 public boolean equals(@CheckForNull Object object) { 595 if (object == this) { 596 return true; 597 } 598 if (object instanceof CharArrayAsList) { 599 CharArrayAsList that = (CharArrayAsList) object; 600 int size = size(); 601 if (that.size() != size) { 602 return false; 603 } 604 for (int i = 0; i < size; i++) { 605 if (array[start + i] != that.array[that.start + i]) { 606 return false; 607 } 608 } 609 return true; 610 } 611 return super.equals(object); 612 } 613 614 @Override 615 public int hashCode() { 616 int result = 1; 617 for (int i = start; i < end; i++) { 618 result = 31 * result + Chars.hashCode(array[i]); 619 } 620 return result; 621 } 622 623 @Override 624 public String toString() { 625 StringBuilder builder = new StringBuilder(size() * 3); 626 builder.append('[').append(array[start]); 627 for (int i = start + 1; i < end; i++) { 628 builder.append(", ").append(array[i]); 629 } 630 return builder.append(']').toString(); 631 } 632 633 char[] toCharArray() { 634 return Arrays.copyOfRange(array, start, end); 635 } 636 637 private static final long serialVersionUID = 0; 638 } 639}