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 java.io.Serializable;
25 import java.util.AbstractList;
26 import java.util.Arrays;
27 import java.util.Collection;
28 import java.util.Collections;
29 import java.util.Comparator;
30 import java.util.List;
31 import java.util.RandomAccess;
32 import javax.annotation.CheckForNull;
33
34 /**
35 * Static utility methods pertaining to {@code boolean} primitives, that are not already found in
36 * either {@link Boolean} or {@link Arrays}.
37 *
38 * <p>See the Guava User Guide article on <a
39 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
40 *
41 * @author Kevin Bourrillion
42 * @since 1.0
43 */
44 @GwtCompatible
45 @ElementTypesAreNonnullByDefault
46 public final class Booleans {
47 private Booleans() {}
48
49 /** Comparators for {@code Boolean} values. */
50 private enum BooleanComparator implements Comparator<Boolean> {
51 TRUE_FIRST(1, "Booleans.trueFirst()"),
52 FALSE_FIRST(-1, "Booleans.falseFirst()");
53
54 private final int trueValue;
55 private final String toString;
56
57 BooleanComparator(int trueValue, String toString) {
58 this.trueValue = trueValue;
59 this.toString = toString;
60 }
61
62 @Override
63 public int compare(Boolean a, Boolean b) {
64 int aVal = a ? trueValue : 0;
65 int bVal = b ? trueValue : 0;
66 return bVal - aVal;
67 }
68
69 @Override
70 public String toString() {
71 return toString;
72 }
73 }
74
75 /**
76 * Returns a {@code Comparator<Boolean>} that sorts {@code true} before {@code false}.
77 *
78 * <p>This is particularly useful in Java 8+ in combination with {@code Comparators.comparing},
79 * e.g. {@code Comparators.comparing(Foo::hasBar, trueFirst())}.
80 *
81 * @since 21.0
82 */
83 @Beta
84 public static Comparator<Boolean> trueFirst() {
85 return BooleanComparator.TRUE_FIRST;
86 }
87
88 /**
89 * Returns a {@code Comparator<Boolean>} that sorts {@code false} before {@code true}.
90 *
91 * <p>This is particularly useful in Java 8+ in combination with {@code Comparators.comparing},
92 * e.g. {@code Comparators.comparing(Foo::hasBar, falseFirst())}.
93 *
94 * @since 21.0
95 */
96 @Beta
97 public static Comparator<Boolean> falseFirst() {
98 return BooleanComparator.FALSE_FIRST;
99 }
100
101 /**
102 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Boolean)
103 * value).hashCode()}.
104 *
105 * <p><b>Java 8 users:</b> use {@link Boolean#hashCode(boolean)} instead.
106 *
107 * @param value a primitive {@code boolean} value
108 * @return a hash code for the value
109 */
110 public static int hashCode(boolean value) {
111 return value ? 1231 : 1237;
112 }
113
114 /**
115 * Compares the two specified {@code boolean} values in the standard way ({@code false} is
116 * considered less than {@code true}). The sign of the value returned is the same as that of
117 * {@code ((Boolean) a).compareTo(b)}.
118 *
119 * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
120 * equivalent {@link Boolean#compare} method instead.
121 *
122 * @param a the first {@code boolean} to compare
123 * @param b the second {@code boolean} to compare
124 * @return a positive number if only {@code a} is {@code true}, a negative number if only {@code
125 * b} is true, or zero if {@code a == b}
126 */
127 public static int compare(boolean a, boolean b) {
128 return (a == b) ? 0 : (a ? 1 : -1);
129 }
130
131 /**
132 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
133 *
134 * <p><b>Note:</b> consider representing the array as a {@link java.util.BitSet} instead,
135 * replacing {@code Booleans.contains(array, true)} with {@code !bitSet.isEmpty()} and {@code
136 * Booleans.contains(array, false)} with {@code bitSet.nextClearBit(0) == sizeOfBitSet}.
137 *
138 * @param array an array of {@code boolean} values, possibly empty
139 * @param target a primitive {@code boolean} value
140 * @return {@code true} if {@code array[i] == target} for some value of {@code i}
141 */
142 public static boolean contains(boolean[] array, boolean target) {
143 for (boolean value : array) {
144 if (value == target) {
145 return true;
146 }
147 }
148 return false;
149 }
150
151 /**
152 * Returns the index of the first appearance of the value {@code target} in {@code array}.
153 *
154 * <p><b>Note:</b> consider representing the array as a {@link java.util.BitSet} instead, and
155 * using {@link java.util.BitSet#nextSetBit(int)} or {@link java.util.BitSet#nextClearBit(int)}.
156 *
157 * @param array an array of {@code boolean} values, possibly empty
158 * @param target a primitive {@code boolean} value
159 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
160 * such index exists.
161 */
162 public static int indexOf(boolean[] array, boolean target) {
163 return indexOf(array, target, 0, array.length);
164 }
165
166 // TODO(kevinb): consider making this public
167 private static int indexOf(boolean[] array, boolean target, int start, int end) {
168 for (int i = start; i < end; i++) {
169 if (array[i] == target) {
170 return i;
171 }
172 }
173 return -1;
174 }
175
176 /**
177 * Returns the start position of the first occurrence of the specified {@code target} within
178 * {@code array}, or {@code -1} if there is no such occurrence.
179 *
180 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
181 * i, i + target.length)} contains exactly the same elements as {@code target}.
182 *
183 * @param array the array to search for the sequence {@code target}
184 * @param target the array to search for as a sub-sequence of {@code array}
185 */
186 public static int indexOf(boolean[] array, boolean[] target) {
187 checkNotNull(array, "array");
188 checkNotNull(target, "target");
189 if (target.length == 0) {
190 return 0;
191 }
192
193 outer:
194 for (int i = 0; i < array.length - target.length + 1; i++) {
195 for (int j = 0; j < target.length; j++) {
196 if (array[i + j] != target[j]) {
197 continue outer;
198 }
199 }
200 return i;
201 }
202 return -1;
203 }
204
205 /**
206 * Returns the index of the last appearance of the value {@code target} in {@code array}.
207 *
208 * @param array an array of {@code boolean} values, possibly empty
209 * @param target a primitive {@code boolean} value
210 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
211 * such index exists.
212 */
213 public static int lastIndexOf(boolean[] array, boolean target) {
214 return lastIndexOf(array, target, 0, array.length);
215 }
216
217 // TODO(kevinb): consider making this public
218 private static int lastIndexOf(boolean[] array, boolean target, int start, int end) {
219 for (int i = end - 1; i >= start; i--) {
220 if (array[i] == target) {
221 return i;
222 }
223 }
224 return -1;
225 }
226
227 /**
228 * Returns the values from each provided array combined into a single array. For example, {@code
229 * concat(new boolean[] {a, b}, new boolean[] {}, new boolean[] {c}} returns the array {@code {a,
230 * b, c}}.
231 *
232 * @param arrays zero or more {@code boolean} arrays
233 * @return a single array containing all the values from the source arrays, in order
234 */
235 public static boolean[] concat(boolean[]... arrays) {
236 int length = 0;
237 for (boolean[] array : arrays) {
238 length += array.length;
239 }
240 boolean[] result = new boolean[length];
241 int pos = 0;
242 for (boolean[] array : arrays) {
243 System.arraycopy(array, 0, result, pos, array.length);
244 pos += array.length;
245 }
246 return result;
247 }
248
249 /**
250 * Returns an array containing the same values as {@code array}, but guaranteed to be of a
251 * specified minimum length. If {@code array} already has a length of at least {@code minLength},
252 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
253 * returned, containing the values of {@code array}, and zeroes in the remaining places.
254 *
255 * @param array the source array
256 * @param minLength the minimum length the returned array must guarantee
257 * @param padding an extra amount to "grow" the array by if growth is necessary
258 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
259 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
260 * minLength}
261 */
262 public static boolean[] ensureCapacity(boolean[] array, int minLength, int padding) {
263 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
264 checkArgument(padding >= 0, "Invalid padding: %s", padding);
265 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
266 }
267
268 /**
269 * Returns a string containing the supplied {@code boolean} values separated by {@code separator}.
270 * For example, {@code join("-", false, true, false)} returns the string {@code
271 * "false-true-false"}.
272 *
273 * @param separator the text that should appear between consecutive values in the resulting string
274 * (but not at the start or end)
275 * @param array an array of {@code boolean} values, possibly empty
276 */
277 public static String join(String separator, boolean... array) {
278 checkNotNull(separator);
279 if (array.length == 0) {
280 return "";
281 }
282
283 // For pre-sizing a builder, just get the right order of magnitude
284 StringBuilder builder = new StringBuilder(array.length * 7);
285 builder.append(array[0]);
286 for (int i = 1; i < array.length; i++) {
287 builder.append(separator).append(array[i]);
288 }
289 return builder.toString();
290 }
291
292 /**
293 * Returns a comparator that compares two {@code boolean} arrays <a
294 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
295 * compares, using {@link #compare(boolean, boolean)}), the first pair of values that follow any
296 * common prefix, or when one array is a prefix of the other, treats the shorter array as the
297 * lesser. For example, {@code [] < [false] < [false, true] < [true]}.
298 *
299 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
300 * support only identity equality), but it is consistent with {@link Arrays#equals(boolean[],
301 * boolean[])}.
302 *
303 * @since 2.0
304 */
305 public static Comparator<boolean[]> lexicographicalComparator() {
306 return LexicographicalComparator.INSTANCE;
307 }
308
309 private enum LexicographicalComparator implements Comparator<boolean[]> {
310 INSTANCE;
311
312 @Override
313 public int compare(boolean[] left, boolean[] right) {
314 int minLength = Math.min(left.length, right.length);
315 for (int i = 0; i < minLength; i++) {
316 int result = Booleans.compare(left[i], right[i]);
317 if (result != 0) {
318 return result;
319 }
320 }
321 return left.length - right.length;
322 }
323
324 @Override
325 public String toString() {
326 return "Booleans.lexicographicalComparator()";
327 }
328 }
329
330 /**
331 * Copies a collection of {@code Boolean} instances into a new array of primitive {@code boolean}
332 * values.
333 *
334 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
335 * Calling this method is as thread-safe as calling that method.
336 *
337 * <p><b>Note:</b> consider representing the collection as a {@link java.util.BitSet} instead.
338 *
339 * @param collection a collection of {@code Boolean} objects
340 * @return an array containing the same values as {@code collection}, in the same order, converted
341 * to primitives
342 * @throws NullPointerException if {@code collection} or any of its elements is null
343 */
344 public static boolean[] toArray(Collection<Boolean> collection) {
345 if (collection instanceof BooleanArrayAsList) {
346 return ((BooleanArrayAsList) collection).toBooleanArray();
347 }
348
349 Object[] boxedArray = collection.toArray();
350 int len = boxedArray.length;
351 boolean[] array = new boolean[len];
352 for (int i = 0; i < len; i++) {
353 // checkNotNull for GWT (do not optimize)
354 array[i] = (Boolean) checkNotNull(boxedArray[i]);
355 }
356 return array;
357 }
358
359 /**
360 * Returns a fixed-size list backed by the specified array, similar to {@link
361 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
362 * set a value to {@code null} will result in a {@link NullPointerException}.
363 *
364 * <p>The returned list maintains the values, but not the identities, of {@code Boolean} objects
365 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
366 * the returned list is unspecified.
367 *
368 * @param backingArray the array to back the list
369 * @return a list view of the array
370 */
371 public static List<Boolean> asList(boolean... backingArray) {
372 if (backingArray.length == 0) {
373 return Collections.emptyList();
374 }
375 return new BooleanArrayAsList(backingArray);
376 }
377
378 @GwtCompatible
379 private static class BooleanArrayAsList extends AbstractList<Boolean>
380 implements RandomAccess, Serializable {
381 final boolean[] array;
382 final int start;
383 final int end;
384
385 BooleanArrayAsList(boolean[] array) {
386 this(array, 0, array.length);
387 }
388
389 BooleanArrayAsList(boolean[] array, int start, int end) {
390 this.array = array;
391 this.start = start;
392 this.end = end;
393 }
394
395 @Override
396 public int size() {
397 return end - start;
398 }
399
400 @Override
401 public boolean isEmpty() {
402 return false;
403 }
404
405 @Override
406 public Boolean get(int index) {
407 checkElementIndex(index, size());
408 return array[start + index];
409 }
410
411 @Override
412 public boolean contains(@CheckForNull Object target) {
413 // Overridden to prevent a ton of boxing
414 return (target instanceof Boolean)
415 && Booleans.indexOf(array, (Boolean) target, start, end) != -1;
416 }
417
418 @Override
419 public int indexOf(@CheckForNull Object target) {
420 // Overridden to prevent a ton of boxing
421 if (target instanceof Boolean) {
422 int i = Booleans.indexOf(array, (Boolean) target, start, end);
423 if (i >= 0) {
424 return i - start;
425 }
426 }
427 return -1;
428 }
429
430 @Override
431 public int lastIndexOf(@CheckForNull Object target) {
432 // Overridden to prevent a ton of boxing
433 if (target instanceof Boolean) {
434 int i = Booleans.lastIndexOf(array, (Boolean) target, start, end);
435 if (i >= 0) {
436 return i - start;
437 }
438 }
439 return -1;
440 }
441
442 @Override
443 public Boolean set(int index, Boolean element) {
444 checkElementIndex(index, size());
445 boolean oldValue = array[start + index];
446 // checkNotNull for GWT (do not optimize)
447 array[start + index] = checkNotNull(element);
448 return oldValue;
449 }
450
451 @Override
452 public List<Boolean> subList(int fromIndex, int toIndex) {
453 int size = size();
454 checkPositionIndexes(fromIndex, toIndex, size);
455 if (fromIndex == toIndex) {
456 return Collections.emptyList();
457 }
458 return new BooleanArrayAsList(array, start + fromIndex, start + toIndex);
459 }
460
461 @Override
462 public boolean equals(@CheckForNull Object object) {
463 if (object == this) {
464 return true;
465 }
466 if (object instanceof BooleanArrayAsList) {
467 BooleanArrayAsList that = (BooleanArrayAsList) object;
468 int size = size();
469 if (that.size() != size) {
470 return false;
471 }
472 for (int i = 0; i < size; i++) {
473 if (array[start + i] != that.array[that.start + i]) {
474 return false;
475 }
476 }
477 return true;
478 }
479 return super.equals(object);
480 }
481
482 @Override
483 public int hashCode() {
484 int result = 1;
485 for (int i = start; i < end; i++) {
486 result = 31 * result + Booleans.hashCode(array[i]);
487 }
488 return result;
489 }
490
491 @Override
492 public String toString() {
493 StringBuilder builder = new StringBuilder(size() * 7);
494 builder.append(array[start] ? "[true" : "[false");
495 for (int i = start + 1; i < end; i++) {
496 builder.append(array[i] ? ", true" : ", false");
497 }
498 return builder.append(']').toString();
499 }
500
501 boolean[] toBooleanArray() {
502 return Arrays.copyOfRange(array, start, end);
503 }
504
505 private static final long serialVersionUID = 0;
506 }
507
508 /**
509 * Returns the number of {@code values} that are {@code true}.
510 *
511 * @since 16.0
512 */
513 @Beta
514 public static int countTrue(boolean... values) {
515 int count = 0;
516 for (boolean value : values) {
517 if (value) {
518 count++;
519 }
520 }
521 return count;
522 }
523
524 /**
525 * Reverses the elements of {@code array}. This is equivalent to {@code
526 * Collections.reverse(Booleans.asList(array))}, but is likely to be more efficient.
527 *
528 * @since 23.1
529 */
530 public static void reverse(boolean[] array) {
531 checkNotNull(array);
532 reverse(array, 0, array.length);
533 }
534
535 /**
536 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
537 * exclusive. This is equivalent to {@code
538 * Collections.reverse(Booleans.asList(array).subList(fromIndex, toIndex))}, but is likely to be
539 * more efficient.
540 *
541 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
542 * {@code toIndex > fromIndex}
543 * @since 23.1
544 */
545 public static void reverse(boolean[] array, int fromIndex, int toIndex) {
546 checkNotNull(array);
547 checkPositionIndexes(fromIndex, toIndex, array.length);
548 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
549 boolean tmp = array[i];
550 array[i] = array[j];
551 array[j] = tmp;
552 }
553 }
554 }