1 /*
2 * Copyright (C) 2008 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.primitives;
16
17 import static com.google.common.base.Preconditions.checkArgument;
18 import static com.google.common.base.Preconditions.checkElementIndex;
19 import static com.google.common.base.Preconditions.checkNotNull;
20 import static com.google.common.base.Preconditions.checkPositionIndexes;
21
22 import com.google.common.annotations.Beta;
23 import com.google.common.annotations.GwtCompatible;
24 import com.google.common.annotations.GwtIncompatible;
25 import java.io.Serializable;
26 import java.util.AbstractList;
27 import java.util.Arrays;
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 import javax.annotation.CheckForNull;
34
35 /**
36 * Static utility methods pertaining to {@code char} primitives, that are not already found in
37 * either {@link Character} or {@link Arrays}.
38 *
39 * <p>All the operations in this class treat {@code char} values strictly numerically; they are
40 * neither Unicode-aware nor locale-dependent.
41 *
42 * <p>See the Guava User Guide article on <a
43 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
44 *
45 * @author Kevin Bourrillion
46 * @since 1.0
47 */
48 @GwtCompatible(emulated = true)
49 @ElementTypesAreNonnullByDefault
50 public final class Chars {
51 private Chars() {}
52
53 /**
54 * The number of bytes required to represent a primitive {@code char} value.
55 *
56 * <p><b>Java 8 users:</b> use {@link Character#BYTES} instead.
57 */
58 public static final int BYTES = Character.SIZE / Byte.SIZE;
59
60 /**
61 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Character)
62 * value).hashCode()}.
63 *
64 * <p><b>Java 8 users:</b> use {@link Character#hashCode(char)} instead.
65 *
66 * @param value a primitive {@code char} value
67 * @return a hash code for the value
68 */
69 public static int hashCode(char value) {
70 return value;
71 }
72
73 /**
74 * Returns the {@code char} value that is equal to {@code value}, if possible.
75 *
76 * @param value any value in the range of the {@code char} type
77 * @return the {@code char} value that equals {@code value}
78 * @throws IllegalArgumentException if {@code value} is greater than {@link Character#MAX_VALUE}
79 * or less than {@link Character#MIN_VALUE}
80 */
81 public static char checkedCast(long value) {
82 char result = (char) value;
83 checkArgument(result == value, "Out of range: %s", value);
84 return result;
85 }
86
87 /**
88 * Returns the {@code char} nearest in value to {@code value}.
89 *
90 * @param value any {@code long} value
91 * @return the same value cast to {@code char} if it is in the range of the {@code char} type,
92 * {@link Character#MAX_VALUE} if it is too large, or {@link Character#MIN_VALUE} if it is too
93 * small
94 */
95 public static char saturatedCast(long value) {
96 if (value > Character.MAX_VALUE) {
97 return Character.MAX_VALUE;
98 }
99 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 }