001 /*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkElementIndex;
021 import static com.google.common.base.Preconditions.checkNotNull;
022 import static com.google.common.base.Preconditions.checkPositionIndexes;
023
024 import com.google.common.annotations.GwtCompatible;
025 import com.google.common.annotations.GwtIncompatible;
026
027 import java.io.Serializable;
028 import java.util.AbstractList;
029 import java.util.Arrays;
030 import java.util.Collection;
031 import java.util.Collections;
032 import java.util.Comparator;
033 import java.util.List;
034 import java.util.RandomAccess;
035
036 /**
037 * Static utility methods pertaining to {@code char} primitives, that are not
038 * already found in either {@link Character} or {@link Arrays}.
039 *
040 * <p>All the operations in this class treat {@code char} values strictly
041 * numerically; they are neither Unicode-aware nor locale-dependent.
042 *
043 * <p>See the Guava User Guide article on <a href=
044 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
045 * primitive utilities</a>.
046 *
047 * @author Kevin Bourrillion
048 * @since 1.0
049 */
050 @GwtCompatible(emulated = true)
051 public final class Chars {
052 private Chars() {}
053
054 /**
055 * The number of bytes required to represent a primitive {@code char}
056 * value.
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
062 * {@code ((Character) value).hashCode()}.
063 *
064 * @param value a primitive {@code char} value
065 * @return a hash code for the value
066 */
067 public static int hashCode(char value) {
068 return value;
069 }
070
071 /**
072 * Returns the {@code char} value that is equal to {@code value}, if possible.
073 *
074 * @param value any value in the range of the {@code char} type
075 * @return the {@code char} value that equals {@code value}
076 * @throws IllegalArgumentException if {@code value} is greater than {@link
077 * Character#MAX_VALUE} or less than {@link Character#MIN_VALUE}
078 */
079 public static char checkedCast(long value) {
080 char result = (char) value;
081 checkArgument(result == value, "Out of range: %s", value);
082 return result;
083 }
084
085 /**
086 * Returns the {@code char} nearest in value to {@code value}.
087 *
088 * @param value any {@code long} value
089 * @return the same value cast to {@code char} if it is in the range of the
090 * {@code char} type, {@link Character#MAX_VALUE} if it is too large,
091 * or {@link Character#MIN_VALUE} if it is too small
092 */
093 public static char saturatedCast(long value) {
094 if (value > Character.MAX_VALUE) {
095 return Character.MAX_VALUE;
096 }
097 if (value < Character.MIN_VALUE) {
098 return Character.MIN_VALUE;
099 }
100 return (char) value;
101 }
102
103 /**
104 * Compares the two specified {@code char} values. The sign of the value
105 * returned is the same as that of {@code ((Character) a).compareTo(b)}.
106 *
107 * @param a the first {@code char} to compare
108 * @param b the second {@code char} to compare
109 * @return a negative value if {@code a} is less than {@code b}; a positive
110 * value if {@code a} is greater than {@code b}; or zero if they are equal
111 */
112 public static int compare(char a, char b) {
113 return a - b; // safe due to restricted range
114 }
115
116 /**
117 * Returns {@code true} if {@code target} is present as an element anywhere in
118 * {@code array}.
119 *
120 * @param array an array of {@code char} values, possibly empty
121 * @param target a primitive {@code char} value
122 * @return {@code true} if {@code array[i] == target} for some value of {@code
123 * i}
124 */
125 public static boolean contains(char[] array, char target) {
126 for (char value : array) {
127 if (value == target) {
128 return true;
129 }
130 }
131 return false;
132 }
133
134 /**
135 * Returns the index of the first appearance of the value {@code target} in
136 * {@code array}.
137 *
138 * @param array an array of {@code char} values, possibly empty
139 * @param target a primitive {@code char} value
140 * @return the least index {@code i} for which {@code array[i] == target}, or
141 * {@code -1} if no such index exists.
142 */
143 public static int indexOf(char[] array, char target) {
144 return indexOf(array, target, 0, array.length);
145 }
146
147 // TODO(kevinb): consider making this public
148 private static int indexOf(
149 char[] array, char target, int start, int end) {
150 for (int i = start; i < end; i++) {
151 if (array[i] == target) {
152 return i;
153 }
154 }
155 return -1;
156 }
157
158 /**
159 * Returns the start position of the first occurrence of the specified {@code
160 * target} within {@code array}, or {@code -1} if there is no such occurrence.
161 *
162 * <p>More formally, returns the lowest index {@code i} such that {@code
163 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
164 * 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
190 * {@code array}.
191 *
192 * @param array an array of {@code char} values, possibly empty
193 * @param target a primitive {@code char} value
194 * @return the greatest index {@code i} for which {@code array[i] == target},
195 * or {@code -1} if no such index exists.
196 */
197 public static int lastIndexOf(char[] array, char target) {
198 return lastIndexOf(array, target, 0, array.length);
199 }
200
201 // TODO(kevinb): consider making this public
202 private static int lastIndexOf(
203 char[] array, char target, int start, int end) {
204 for (int i = end - 1; i >= start; i--) {
205 if (array[i] == target) {
206 return i;
207 }
208 }
209 return -1;
210 }
211
212 /**
213 * Returns the least value present in {@code array}.
214 *
215 * @param array a <i>nonempty</i> array of {@code char} values
216 * @return the value present in {@code array} that is less than or equal to
217 * every other value in the array
218 * @throws IllegalArgumentException if {@code array} is empty
219 */
220 public static char min(char... array) {
221 checkArgument(array.length > 0);
222 char min = array[0];
223 for (int i = 1; i < array.length; i++) {
224 if (array[i] < min) {
225 min = array[i];
226 }
227 }
228 return min;
229 }
230
231 /**
232 * Returns the greatest value present in {@code array}.
233 *
234 * @param array a <i>nonempty</i> array of {@code char} values
235 * @return the value present in {@code array} that is greater than or equal to
236 * every other value in the array
237 * @throws IllegalArgumentException if {@code array} is empty
238 */
239 public static char max(char... array) {
240 checkArgument(array.length > 0);
241 char max = array[0];
242 for (int i = 1; i < array.length; i++) {
243 if (array[i] > max) {
244 max = array[i];
245 }
246 }
247 return max;
248 }
249
250 /**
251 * Returns the values from each provided array combined into a single array.
252 * For example, {@code concat(new char[] {a, b}, new char[] {}, new
253 * char[] {c}} returns the array {@code {a, b, c}}.
254 *
255 * @param arrays zero or more {@code char} arrays
256 * @return a single array containing all the values from the source arrays, in
257 * order
258 */
259 public static char[] concat(char[]... arrays) {
260 int length = 0;
261 for (char[] array : arrays) {
262 length += array.length;
263 }
264 char[] result = new char[length];
265 int pos = 0;
266 for (char[] array : arrays) {
267 System.arraycopy(array, 0, result, pos, array.length);
268 pos += array.length;
269 }
270 return result;
271 }
272
273 /**
274 * Returns a big-endian representation of {@code value} in a 2-element byte
275 * array; equivalent to {@code
276 * ByteBuffer.allocate(2).putChar(value).array()}. For example, the input
277 * value {@code '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
278 *
279 * <p>If you need to convert and concatenate several values (possibly even of
280 * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
281 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
282 * buffer.
283 */
284 @GwtIncompatible("doesn't work")
285 public static byte[] toByteArray(char value) {
286 return new byte[] {
287 (byte) (value >> 8),
288 (byte) value};
289 }
290
291 /**
292 * Returns the {@code char} value whose big-endian representation is
293 * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
294 * ByteBuffer.wrap(bytes).getChar()}. For example, the input byte array
295 * {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
296 *
297 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
298 * library exposes much more flexibility at little cost in readability.
299 *
300 * @throws IllegalArgumentException if {@code bytes} has fewer than 2
301 * elements
302 */
303 @GwtIncompatible("doesn't work")
304 public static char fromByteArray(byte[] bytes) {
305 checkArgument(bytes.length >= BYTES,
306 "array too small: %s < %s", bytes.length, BYTES);
307 return fromBytes(bytes[0], bytes[1]);
308 }
309
310 /**
311 * Returns the {@code char} value whose byte representation is the given 2
312 * bytes, in big-endian order; equivalent to {@code Chars.fromByteArray(new
313 * byte[] {b1, b2})}.
314 *
315 * @since 7.0
316 */
317 @GwtIncompatible("doesn't work")
318 public static char fromBytes(byte b1, byte b2) {
319 return (char) ((b1 << 8) | (b2 & 0xFF));
320 }
321
322 /**
323 * Returns an array containing the same values as {@code array}, but
324 * guaranteed to be of a specified minimum length. If {@code array} already
325 * has a length of at least {@code minLength}, it is returned directly.
326 * Otherwise, a new array of size {@code minLength + padding} is returned,
327 * containing the values of {@code array}, and zeroes in the remaining places.
328 *
329 * @param array the source array
330 * @param minLength the minimum length the returned array must guarantee
331 * @param padding an extra amount to "grow" the array by if growth is
332 * necessary
333 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
334 * negative
335 * @return an array containing the values of {@code array}, with guaranteed
336 * minimum length {@code minLength}
337 */
338 public static char[] ensureCapacity(
339 char[] array, int minLength, int padding) {
340 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
341 checkArgument(padding >= 0, "Invalid padding: %s", padding);
342 return (array.length < minLength)
343 ? copyOf(array, minLength + padding)
344 : array;
345 }
346
347 // Arrays.copyOf() requires Java 6
348 private static char[] copyOf(char[] original, int length) {
349 char[] copy = new char[length];
350 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
351 return copy;
352 }
353
354 /**
355 * Returns a string containing the supplied {@code char} values separated
356 * by {@code separator}. For example, {@code join("-", '1', '2', '3')} returns
357 * the string {@code "1-2-3"}.
358 *
359 * @param separator the text that should appear between consecutive values in
360 * the resulting string (but not at the start or end)
361 * @param array an array of {@code char} values, possibly empty
362 */
363 public static String join(String separator, char... array) {
364 checkNotNull(separator);
365 int len = array.length;
366 if (len == 0) {
367 return "";
368 }
369
370 StringBuilder builder
371 = new StringBuilder(len + separator.length() * (len - 1));
372 builder.append(array[0]);
373 for (int i = 1; i < len; i++) {
374 builder.append(separator).append(array[i]);
375 }
376 return builder.toString();
377 }
378
379 /**
380 * Returns a comparator that compares two {@code char} arrays
381 * lexicographically. That is, it compares, using {@link
382 * #compare(char, char)}), the first pair of values that follow any
383 * common prefix, or when one array is a prefix of the other, treats the
384 * shorter array as the lesser. For example,
385 * {@code [] < ['a'] < ['a', 'b'] < ['b']}.
386 *
387 * <p>The returned comparator is inconsistent with {@link
388 * Object#equals(Object)} (since arrays support only identity equality), but
389 * it is consistent with {@link Arrays#equals(char[], char[])}.
390 *
391 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
392 * Lexicographical order article at Wikipedia</a>
393 * @since 2.0
394 */
395 public static Comparator<char[]> lexicographicalComparator() {
396 return LexicographicalComparator.INSTANCE;
397 }
398
399 private enum LexicographicalComparator implements Comparator<char[]> {
400 INSTANCE;
401
402 @Override
403 public int compare(char[] left, char[] right) {
404 int minLength = Math.min(left.length, right.length);
405 for (int i = 0; i < minLength; i++) {
406 int result = Chars.compare(left[i], right[i]);
407 if (result != 0) {
408 return result;
409 }
410 }
411 return left.length - right.length;
412 }
413 }
414
415 /**
416 * Copies a collection of {@code Character} instances into a new array of
417 * primitive {@code char} values.
418 *
419 * <p>Elements are copied from the argument collection as if by {@code
420 * collection.toArray()}. Calling this method is as thread-safe as calling
421 * that method.
422 *
423 * @param collection a collection of {@code Character} objects
424 * @return an array containing the same values as {@code collection}, in the
425 * same order, converted to primitives
426 * @throws NullPointerException if {@code collection} or any of its elements
427 * is null
428 */
429 public static char[] toArray(Collection<Character> collection) {
430 if (collection instanceof CharArrayAsList) {
431 return ((CharArrayAsList) collection).toCharArray();
432 }
433
434 Object[] boxedArray = collection.toArray();
435 int len = boxedArray.length;
436 char[] array = new char[len];
437 for (int i = 0; i < len; i++) {
438 // checkNotNull for GWT (do not optimize)
439 array[i] = (Character) checkNotNull(boxedArray[i]);
440 }
441 return array;
442 }
443
444 /**
445 * Returns a fixed-size list backed by the specified array, similar to {@link
446 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
447 * but any attempt to set a value to {@code null} will result in a {@link
448 * NullPointerException}.
449 *
450 * <p>The returned list maintains the values, but not the identities, of
451 * {@code Character} objects written to or read from it. For example, whether
452 * {@code list.get(0) == list.get(0)} is true for the returned list is
453 * unspecified.
454 *
455 * @param backingArray the array to back the list
456 * @return a list view of the array
457 */
458 public static List<Character> asList(char... backingArray) {
459 if (backingArray.length == 0) {
460 return Collections.emptyList();
461 }
462 return new CharArrayAsList(backingArray);
463 }
464
465 @GwtCompatible
466 private static class CharArrayAsList extends AbstractList<Character>
467 implements RandomAccess, Serializable {
468 final char[] array;
469 final int start;
470 final int end;
471
472 CharArrayAsList(char[] array) {
473 this(array, 0, array.length);
474 }
475
476 CharArrayAsList(char[] array, int start, int end) {
477 this.array = array;
478 this.start = start;
479 this.end = end;
480 }
481
482 @Override public int size() {
483 return end - start;
484 }
485
486 @Override public boolean isEmpty() {
487 return false;
488 }
489
490 @Override public Character get(int index) {
491 checkElementIndex(index, size());
492 return array[start + index];
493 }
494
495 @Override public boolean contains(Object target) {
496 // Overridden to prevent a ton of boxing
497 return (target instanceof Character)
498 && Chars.indexOf(array, (Character) target, start, end) != -1;
499 }
500
501 @Override public int indexOf(Object target) {
502 // Overridden to prevent a ton of boxing
503 if (target instanceof Character) {
504 int i = Chars.indexOf(array, (Character) target, start, end);
505 if (i >= 0) {
506 return i - start;
507 }
508 }
509 return -1;
510 }
511
512 @Override public int lastIndexOf(Object target) {
513 // Overridden to prevent a ton of boxing
514 if (target instanceof Character) {
515 int i = Chars.lastIndexOf(array, (Character) target, start, end);
516 if (i >= 0) {
517 return i - start;
518 }
519 }
520 return -1;
521 }
522
523 @Override public Character set(int index, Character element) {
524 checkElementIndex(index, size());
525 char oldValue = array[start + index];
526 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
527 return oldValue;
528 }
529
530 @Override public List<Character> subList(int fromIndex, int toIndex) {
531 int size = size();
532 checkPositionIndexes(fromIndex, toIndex, size);
533 if (fromIndex == toIndex) {
534 return Collections.emptyList();
535 }
536 return new CharArrayAsList(array, start + fromIndex, start + toIndex);
537 }
538
539 @Override public boolean equals(Object object) {
540 if (object == this) {
541 return true;
542 }
543 if (object instanceof CharArrayAsList) {
544 CharArrayAsList that = (CharArrayAsList) object;
545 int size = size();
546 if (that.size() != size) {
547 return false;
548 }
549 for (int i = 0; i < size; i++) {
550 if (array[start + i] != that.array[that.start + i]) {
551 return false;
552 }
553 }
554 return true;
555 }
556 return super.equals(object);
557 }
558
559 @Override public int hashCode() {
560 int result = 1;
561 for (int i = start; i < end; i++) {
562 result = 31 * result + Chars.hashCode(array[i]);
563 }
564 return result;
565 }
566
567 @Override public String toString() {
568 StringBuilder builder = new StringBuilder(size() * 3);
569 builder.append('[').append(array[start]);
570 for (int i = start + 1; i < end; i++) {
571 builder.append(", ").append(array[i]);
572 }
573 return builder.append(']').toString();
574 }
575
576 char[] toCharArray() {
577 // Arrays.copyOfRange() requires Java 6
578 int size = size();
579 char[] result = new char[size];
580 System.arraycopy(array, start, result, 0, size);
581 return result;
582 }
583
584 private static final long serialVersionUID = 0;
585 }
586 }