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
026 import java.io.Serializable;
027 import java.util.AbstractList;
028 import java.util.Arrays;
029 import java.util.BitSet;
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 boolean} primitives, that are not
038 * already found in either {@link Boolean} or {@link Arrays}.
039 *
040 * <p>See the Guava User Guide article on <a href=
041 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
042 * primitive utilities</a>.
043 *
044 * @author Kevin Bourrillion
045 * @since 1.0
046 */
047 @GwtCompatible
048 public final class Booleans {
049 private Booleans() {}
050
051 /**
052 * Returns a hash code for {@code value}; equal to the result of invoking
053 * {@code ((Boolean) value).hashCode()}.
054 *
055 * @param value a primitive {@code boolean} value
056 * @return a hash code for the value
057 */
058 public static int hashCode(boolean value) {
059 return value ? 1231 : 1237;
060 }
061
062 /**
063 * Compares the two specified {@code boolean} values in the standard way
064 * ({@code false} is considered less than {@code true}). The sign of the
065 * value returned is the same as that of {@code ((Boolean) a).compareTo(b)}.
066 *
067 * @param a the first {@code boolean} to compare
068 * @param b the second {@code boolean} to compare
069 * @return a positive number if only {@code a} is {@code true}, a negative
070 * number if only {@code b} is true, or zero if {@code a == b}
071 */
072 public static int compare(boolean a, boolean b) {
073 return (a == b) ? 0 : (a ? 1 : -1);
074 }
075
076 /**
077 * Returns {@code true} if {@code target} is present as an element anywhere in
078 * {@code array}.
079 *
080 * <p><b>Note:</b> consider representing the array as a {@link
081 * BitSet} instead, replacing {@code Booleans.contains(array, true)}
082 * with {@code !bitSet.isEmpty()} and {@code Booleans.contains(array, false)}
083 * with {@code bitSet.nextClearBit(0) == sizeOfBitSet}.
084 *
085 * @param array an array of {@code boolean} values, possibly empty
086 * @param target a primitive {@code boolean} value
087 * @return {@code true} if {@code array[i] == target} for some value of {@code
088 * i}
089 */
090 public static boolean contains(boolean[] array, boolean target) {
091 for (boolean value : array) {
092 if (value == target) {
093 return true;
094 }
095 }
096 return false;
097 }
098
099 /**
100 * Returns the index of the first appearance of the value {@code target} in
101 * {@code array}.
102 *
103 * <p><b>Note:</b> consider representing the array as a {@link BitSet}
104 * instead, and using {@link BitSet#nextSetBit(int)} or {@link
105 * BitSet#nextClearBit(int)}.
106 *
107 * @param array an array of {@code boolean} values, possibly empty
108 * @param target a primitive {@code boolean} value
109 * @return the least index {@code i} for which {@code array[i] == target}, or
110 * {@code -1} if no such index exists.
111 */
112 public static int indexOf(boolean[] array, boolean target) {
113 return indexOf(array, target, 0, array.length);
114 }
115
116 // TODO(kevinb): consider making this public
117 private static int indexOf(
118 boolean[] array, boolean target, int start, int end) {
119 for (int i = start; i < end; i++) {
120 if (array[i] == target) {
121 return i;
122 }
123 }
124 return -1;
125 }
126
127 /**
128 * Returns the start position of the first occurrence of the specified {@code
129 * target} within {@code array}, or {@code -1} if there is no such occurrence.
130 *
131 * <p>More formally, returns the lowest index {@code i} such that {@code
132 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
133 * the same elements as {@code target}.
134 *
135 * @param array the array to search for the sequence {@code target}
136 * @param target the array to search for as a sub-sequence of {@code array}
137 */
138 public static int indexOf(boolean[] array, boolean[] target) {
139 checkNotNull(array, "array");
140 checkNotNull(target, "target");
141 if (target.length == 0) {
142 return 0;
143 }
144
145 outer:
146 for (int i = 0; i < array.length - target.length + 1; i++) {
147 for (int j = 0; j < target.length; j++) {
148 if (array[i + j] != target[j]) {
149 continue outer;
150 }
151 }
152 return i;
153 }
154 return -1;
155 }
156
157 /**
158 * Returns the index of the last appearance of the value {@code target} in
159 * {@code array}.
160 *
161 * @param array an array of {@code boolean} values, possibly empty
162 * @param target a primitive {@code boolean} value
163 * @return the greatest index {@code i} for which {@code array[i] == target},
164 * or {@code -1} if no such index exists.
165 */
166 public static int lastIndexOf(boolean[] array, boolean target) {
167 return lastIndexOf(array, target, 0, array.length);
168 }
169
170 // TODO(kevinb): consider making this public
171 private static int lastIndexOf(
172 boolean[] array, boolean target, int start, int end) {
173 for (int i = end - 1; i >= start; i--) {
174 if (array[i] == target) {
175 return i;
176 }
177 }
178 return -1;
179 }
180
181 /**
182 * Returns the values from each provided array combined into a single array.
183 * For example, {@code concat(new boolean[] {a, b}, new boolean[] {}, new
184 * boolean[] {c}} returns the array {@code {a, b, c}}.
185 *
186 * @param arrays zero or more {@code boolean} arrays
187 * @return a single array containing all the values from the source arrays, in
188 * order
189 */
190 public static boolean[] concat(boolean[]... arrays) {
191 int length = 0;
192 for (boolean[] array : arrays) {
193 length += array.length;
194 }
195 boolean[] result = new boolean[length];
196 int pos = 0;
197 for (boolean[] array : arrays) {
198 System.arraycopy(array, 0, result, pos, array.length);
199 pos += array.length;
200 }
201 return result;
202 }
203
204 /**
205 * Returns an array containing the same values as {@code array}, but
206 * guaranteed to be of a specified minimum length. If {@code array} already
207 * has a length of at least {@code minLength}, it is returned directly.
208 * Otherwise, a new array of size {@code minLength + padding} is returned,
209 * containing the values of {@code array}, and zeroes in the remaining places.
210 *
211 * @param array the source array
212 * @param minLength the minimum length the returned array must guarantee
213 * @param padding an extra amount to "grow" the array by if growth is
214 * necessary
215 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
216 * negative
217 * @return an array containing the values of {@code array}, with guaranteed
218 * minimum length {@code minLength}
219 */
220 public static boolean[] ensureCapacity(
221 boolean[] array, int minLength, int padding) {
222 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
223 checkArgument(padding >= 0, "Invalid padding: %s", padding);
224 return (array.length < minLength)
225 ? copyOf(array, minLength + padding)
226 : array;
227 }
228
229 // Arrays.copyOf() requires Java 6
230 private static boolean[] copyOf(boolean[] original, int length) {
231 boolean[] copy = new boolean[length];
232 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
233 return copy;
234 }
235
236 /**
237 * Returns a string containing the supplied {@code boolean} values separated
238 * by {@code separator}. For example, {@code join("-", false, true, false)}
239 * returns the string {@code "false-true-false"}.
240 *
241 * @param separator the text that should appear between consecutive values in
242 * the resulting string (but not at the start or end)
243 * @param array an array of {@code boolean} values, possibly empty
244 */
245 public static String join(String separator, boolean... array) {
246 checkNotNull(separator);
247 if (array.length == 0) {
248 return "";
249 }
250
251 // For pre-sizing a builder, just get the right order of magnitude
252 StringBuilder builder = new StringBuilder(array.length * 7);
253 builder.append(array[0]);
254 for (int i = 1; i < array.length; i++) {
255 builder.append(separator).append(array[i]);
256 }
257 return builder.toString();
258 }
259
260 /**
261 * Returns a comparator that compares two {@code boolean} arrays
262 * lexicographically. That is, it compares, using {@link
263 * #compare(boolean, boolean)}), the first pair of values that follow any
264 * common prefix, or when one array is a prefix of the other, treats the
265 * shorter array as the lesser. For example,
266 * {@code [] < [false] < [false, true] < [true]}.
267 *
268 * <p>The returned comparator is inconsistent with {@link
269 * Object#equals(Object)} (since arrays support only identity equality), but
270 * it is consistent with {@link Arrays#equals(boolean[], boolean[])}.
271 *
272 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
273 * Lexicographical order article at Wikipedia</a>
274 * @since 2.0
275 */
276 public static Comparator<boolean[]> lexicographicalComparator() {
277 return LexicographicalComparator.INSTANCE;
278 }
279
280 private enum LexicographicalComparator implements Comparator<boolean[]> {
281 INSTANCE;
282
283 @Override
284 public int compare(boolean[] left, boolean[] right) {
285 int minLength = Math.min(left.length, right.length);
286 for (int i = 0; i < minLength; i++) {
287 int result = Booleans.compare(left[i], right[i]);
288 if (result != 0) {
289 return result;
290 }
291 }
292 return left.length - right.length;
293 }
294 }
295
296 /**
297 * Copies a collection of {@code Boolean} instances into a new array of
298 * primitive {@code boolean} values.
299 *
300 * <p>Elements are copied from the argument collection as if by {@code
301 * collection.toArray()}. Calling this method is as thread-safe as calling
302 * that method.
303 *
304 * <p><b>Note:</b> consider representing the collection as a {@link
305 * BitSet} instead.
306 *
307 * @param collection a collection of {@code Boolean} objects
308 * @return an array containing the same values as {@code collection}, in the
309 * same order, converted to primitives
310 * @throws NullPointerException if {@code collection} or any of its elements
311 * is null
312 */
313 public static boolean[] toArray(Collection<Boolean> collection) {
314 if (collection instanceof BooleanArrayAsList) {
315 return ((BooleanArrayAsList) collection).toBooleanArray();
316 }
317
318 Object[] boxedArray = collection.toArray();
319 int len = boxedArray.length;
320 boolean[] array = new boolean[len];
321 for (int i = 0; i < len; i++) {
322 // checkNotNull for GWT (do not optimize)
323 array[i] = (Boolean) checkNotNull(boxedArray[i]);
324 }
325 return array;
326 }
327
328 /**
329 * Returns a fixed-size list backed by the specified array, similar to {@link
330 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
331 * but any attempt to set a value to {@code null} will result in a {@link
332 * NullPointerException}.
333 *
334 * <p>The returned list maintains the values, but not the identities, of
335 * {@code Boolean} objects written to or read from it. For example, whether
336 * {@code list.get(0) == list.get(0)} is true for the returned list is
337 * unspecified.
338 *
339 * @param backingArray the array to back the list
340 * @return a list view of the array
341 */
342 public static List<Boolean> asList(boolean... backingArray) {
343 if (backingArray.length == 0) {
344 return Collections.emptyList();
345 }
346 return new BooleanArrayAsList(backingArray);
347 }
348
349 @GwtCompatible
350 private static class BooleanArrayAsList extends AbstractList<Boolean>
351 implements RandomAccess, Serializable {
352 final boolean[] array;
353 final int start;
354 final int end;
355
356 BooleanArrayAsList(boolean[] array) {
357 this(array, 0, array.length);
358 }
359
360 BooleanArrayAsList(boolean[] array, int start, int end) {
361 this.array = array;
362 this.start = start;
363 this.end = end;
364 }
365
366 @Override public int size() {
367 return end - start;
368 }
369
370 @Override public boolean isEmpty() {
371 return false;
372 }
373
374 @Override public Boolean get(int index) {
375 checkElementIndex(index, size());
376 return array[start + index];
377 }
378
379 @Override public boolean contains(Object target) {
380 // Overridden to prevent a ton of boxing
381 return (target instanceof Boolean)
382 && Booleans.indexOf(array, (Boolean) target, start, end) != -1;
383 }
384
385 @Override public int indexOf(Object target) {
386 // Overridden to prevent a ton of boxing
387 if (target instanceof Boolean) {
388 int i = Booleans.indexOf(array, (Boolean) target, start, end);
389 if (i >= 0) {
390 return i - start;
391 }
392 }
393 return -1;
394 }
395
396 @Override public int lastIndexOf(Object target) {
397 // Overridden to prevent a ton of boxing
398 if (target instanceof Boolean) {
399 int i = Booleans.lastIndexOf(array, (Boolean) target, start, end);
400 if (i >= 0) {
401 return i - start;
402 }
403 }
404 return -1;
405 }
406
407 @Override public Boolean set(int index, Boolean element) {
408 checkElementIndex(index, size());
409 boolean oldValue = array[start + index];
410 // checkNotNull for GWT (do not optimize)
411 array[start + index] = checkNotNull(element);
412 return oldValue;
413 }
414
415 @Override public List<Boolean> subList(int fromIndex, int toIndex) {
416 int size = size();
417 checkPositionIndexes(fromIndex, toIndex, size);
418 if (fromIndex == toIndex) {
419 return Collections.emptyList();
420 }
421 return new BooleanArrayAsList(array, start + fromIndex, start + toIndex);
422 }
423
424 @Override public boolean equals(Object object) {
425 if (object == this) {
426 return true;
427 }
428 if (object instanceof BooleanArrayAsList) {
429 BooleanArrayAsList that = (BooleanArrayAsList) object;
430 int size = size();
431 if (that.size() != size) {
432 return false;
433 }
434 for (int i = 0; i < size; i++) {
435 if (array[start + i] != that.array[that.start + i]) {
436 return false;
437 }
438 }
439 return true;
440 }
441 return super.equals(object);
442 }
443
444 @Override public int hashCode() {
445 int result = 1;
446 for (int i = start; i < end; i++) {
447 result = 31 * result + Booleans.hashCode(array[i]);
448 }
449 return result;
450 }
451
452 @Override public String toString() {
453 StringBuilder builder = new StringBuilder(size() * 7);
454 builder.append(array[start] ? "[true" : "[false");
455 for (int i = start + 1; i < end; i++) {
456 builder.append(array[i] ? ", true" : ", false");
457 }
458 return builder.append(']').toString();
459 }
460
461 boolean[] toBooleanArray() {
462 // Arrays.copyOfRange() is not available under GWT
463 int size = size();
464 boolean[] result = new boolean[size];
465 System.arraycopy(array, start, result, 0, size);
466 return result;
467 }
468
469 private static final long serialVersionUID = 0;
470 }
471 }