001 /*
002 * Copyright (C) 2008 Google Inc.
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 * @author Kevin Bourrillion
041 * @since 1
042 */
043 @GwtCompatible
044 public final class Booleans {
045 private Booleans() {}
046
047 /**
048 * Returns a hash code for {@code value}; equal to the result of invoking
049 * {@code ((Boolean) value).hashCode()}.
050 *
051 * @param value a primitive {@code boolean} value
052 * @return a hash code for the value
053 */
054 public static int hashCode(boolean value) {
055 return value ? 1231 : 1237;
056 }
057
058 /**
059 * Compares the two specified {@code boolean} values in the standard way
060 * ({@code false} is considered less than {@code true}). The sign of the
061 * value returned is the same as that of {@code ((Boolean) a).compareTo(b)}.
062 *
063 * @param a the first {@code boolean} to compare
064 * @param b the second {@code boolean} to compare
065 * @return a positive number if only {@code a} is {@code true}, a negative
066 * number if only {@code b} is true, or zero if {@code a == b}
067 */
068 public static int compare(boolean a, boolean b) {
069 return (a == b) ? 0 : (a ? 1 : -1);
070 }
071
072 /**
073 * Returns {@code true} if {@code target} is present as an element anywhere in
074 * {@code array}.
075 *
076 * <p><b>Note:</b> consider representing the array as a {@link
077 * BitSet} instead, replacing {@code Booleans.contains(array, true)}
078 * with {@code !bitSet.isEmpty()} and {@code Booleans.contains(array, false)}
079 * with {@code bitSet.nextClearBit(0) == sizeOfBitSet}.
080 *
081 * @param array an array of {@code boolean} values, possibly empty
082 * @param target a primitive {@code boolean} value
083 * @return {@code true} if {@code array[i] == target} for some value of {@code
084 * i}
085 */
086 public static boolean contains(boolean[] array, boolean target) {
087 for (boolean value : array) {
088 if (value == target) {
089 return true;
090 }
091 }
092 return false;
093 }
094
095 /**
096 * Returns the index of the first appearance of the value {@code target} in
097 * {@code array}.
098 *
099 * <p><b>Note:</b> consider representing the array as a {@link BitSet}
100 * instead, and using {@link BitSet#nextSetBit(int)} or {@link
101 * BitSet#nextClearBit(int)}.
102 *
103 * @param array an array of {@code boolean} values, possibly empty
104 * @param target a primitive {@code boolean} value
105 * @return the least index {@code i} for which {@code array[i] == target}, or
106 * {@code -1} if no such index exists.
107 */
108 public static int indexOf(boolean[] array, boolean target) {
109 return indexOf(array, target, 0, array.length);
110 }
111
112 // TODO: consider making this public
113 private static int indexOf(
114 boolean[] array, boolean target, int start, int end) {
115 for (int i = start; i < end; i++) {
116 if (array[i] == target) {
117 return i;
118 }
119 }
120 return -1;
121 }
122
123 /**
124 * Returns the start position of the first occurrence of the specified {@code
125 * target} within {@code array}, or {@code -1} if there is no such occurrence.
126 *
127 * <p>More formally, returns the lowest index {@code i} such that {@code
128 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
129 * the same elements as {@code target}.
130 *
131 * @param array the array to search for the sequence {@code target}
132 * @param target the array to search for as a sub-sequence of {@code array}
133 */
134 public static int indexOf(boolean[] array, boolean[] target) {
135 checkNotNull(array, "array");
136 checkNotNull(target, "target");
137 if (target.length == 0) {
138 return 0;
139 }
140
141 outer:
142 for (int i = 0; i < array.length - target.length + 1; i++) {
143 for (int j = 0; j < target.length; j++) {
144 if (array[i + j] != target[j]) {
145 continue outer;
146 }
147 }
148 return i;
149 }
150 return -1;
151 }
152
153 /**
154 * Returns the index of the last appearance of the value {@code target} in
155 * {@code array}.
156 *
157 * @param array an array of {@code boolean} values, possibly empty
158 * @param target a primitive {@code boolean} value
159 * @return the greatest index {@code i} for which {@code array[i] == target},
160 * or {@code -1} if no such index exists.
161 */
162 public static int lastIndexOf(boolean[] array, boolean target) {
163 return lastIndexOf(array, target, 0, array.length);
164 }
165
166 // TODO: consider making this public
167 private static int lastIndexOf(
168 boolean[] array, boolean target, int start, int end) {
169 for (int i = end - 1; i >= start; i--) {
170 if (array[i] == target) {
171 return i;
172 }
173 }
174 return -1;
175 }
176
177 /**
178 * Returns the values from each provided array combined into a single array.
179 * For example, {@code concat(new boolean[] {a, b}, new boolean[] {}, new
180 * boolean[] {c}} returns the array {@code {a, b, c}}.
181 *
182 * @param arrays zero or more {@code boolean} arrays
183 * @return a single array containing all the values from the source arrays, in
184 * order
185 */
186 public static boolean[] concat(boolean[]... arrays) {
187 int length = 0;
188 for (boolean[] array : arrays) {
189 length += array.length;
190 }
191 boolean[] result = new boolean[length];
192 int pos = 0;
193 for (boolean[] array : arrays) {
194 System.arraycopy(array, 0, result, pos, array.length);
195 pos += array.length;
196 }
197 return result;
198 }
199
200 /**
201 * Returns an array containing the same values as {@code array}, but
202 * guaranteed to be of a specified minimum length. If {@code array} already
203 * has a length of at least {@code minLength}, it is returned directly.
204 * Otherwise, a new array of size {@code minLength + padding} is returned,
205 * containing the values of {@code array}, and zeroes in the remaining places.
206 *
207 * @param array the source array
208 * @param minLength the minimum length the returned array must guarantee
209 * @param padding an extra amount to "grow" the array by if growth is
210 * necessary
211 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
212 * negative
213 * @return an array containing the values of {@code array}, with guaranteed
214 * minimum length {@code minLength}
215 */
216 public static boolean[] ensureCapacity(
217 boolean[] array, int minLength, int padding) {
218 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
219 checkArgument(padding >= 0, "Invalid padding: %s", padding);
220 return (array.length < minLength)
221 ? copyOf(array, minLength + padding)
222 : array;
223 }
224
225 // Arrays.copyOf() requires Java 6
226 private static boolean[] copyOf(boolean[] original, int length) {
227 boolean[] copy = new boolean[length];
228 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
229 return copy;
230 }
231
232 /**
233 * Returns a string containing the supplied {@code boolean} values separated
234 * by {@code separator}. For example, {@code join("-", false, true, false)}
235 * returns the string {@code "false-true-false"}.
236 *
237 * @param separator the text that should appear between consecutive values in
238 * the resulting string (but not at the start or end)
239 * @param array an array of {@code boolean} values, possibly empty
240 */
241 public static String join(String separator, boolean... array) {
242 checkNotNull(separator);
243 if (array.length == 0) {
244 return "";
245 }
246
247 // For pre-sizing a builder, just get the right order of magnitude
248 StringBuilder builder = new StringBuilder(array.length * 7);
249 builder.append(array[0]);
250 for (int i = 1; i < array.length; i++) {
251 builder.append(separator).append(array[i]);
252 }
253 return builder.toString();
254 }
255
256 /**
257 * Returns a comparator that compares two {@code boolean} arrays
258 * lexicographically. That is, it compares, using {@link
259 * #compare(boolean, boolean)}), the first pair of values that follow any
260 * common prefix, or when one array is a prefix of the other, treats the
261 * shorter array as the lesser. For example,
262 * {@code [] < [false] < [false, true] < [true]}.
263 *
264 * <p>The returned comparator is inconsistent with {@link
265 * Object#equals(Object)} (since arrays support only identity equality), but
266 * it is consistent with {@link Arrays#equals(boolean[], boolean[])}.
267 *
268 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
269 * Lexicographical order</a> article at Wikipedia
270 * @since 2
271 */
272 public static Comparator<boolean[]> lexicographicalComparator() {
273 return LexicographicalComparator.INSTANCE;
274 }
275
276 private enum LexicographicalComparator implements Comparator<boolean[]> {
277 INSTANCE;
278
279 public int compare(boolean[] left, boolean[] right) {
280 int minLength = Math.min(left.length, right.length);
281 for (int i = 0; i < minLength; i++) {
282 int result = Booleans.compare(left[i], right[i]);
283 if (result != 0) {
284 return result;
285 }
286 }
287 return left.length - right.length;
288 }
289 }
290
291 /**
292 * Copies a collection of {@code Boolean} instances into a new array of
293 * primitive {@code boolean} values.
294 *
295 * <p>Elements are copied from the argument collection as if by {@code
296 * collection.toArray()}. Calling this method is as thread-safe as calling
297 * that method.
298 *
299 * <p><b>Note:</b> consider representing the collection as a {@link
300 * BitSet} instead.
301 *
302 * @param collection a collection of {@code Boolean} objects
303 * @return an array containing the same values as {@code collection}, in the
304 * same order, converted to primitives
305 * @throws NullPointerException if {@code collection} or any of its elements
306 * is null
307 */
308 public static boolean[] toArray(Collection<Boolean> collection) {
309 if (collection instanceof BooleanArrayAsList) {
310 return ((BooleanArrayAsList) collection).toBooleanArray();
311 }
312
313 Object[] boxedArray = collection.toArray();
314 int len = boxedArray.length;
315 boolean[] array = new boolean[len];
316 for (int i = 0; i < len; i++) {
317 array[i] = (Boolean) boxedArray[i];
318 }
319 return array;
320 }
321
322 /**
323 * Returns a fixed-size list backed by the specified array, similar to {@link
324 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
325 * but any attempt to set a value to {@code null} will result in a {@link
326 * NullPointerException}.
327 *
328 * <p>The returned list maintains the values, but not the identities, of
329 * {@code Boolean} objects written to or read from it. For example, whether
330 * {@code list.get(0) == list.get(0)} is true for the returned list is
331 * unspecified.
332 *
333 * @param backingArray the array to back the list
334 * @return a list view of the array
335 */
336 public static List<Boolean> asList(boolean... backingArray) {
337 if (backingArray.length == 0) {
338 return Collections.emptyList();
339 }
340 return new BooleanArrayAsList(backingArray);
341 }
342
343 @GwtCompatible
344 private static class BooleanArrayAsList extends AbstractList<Boolean>
345 implements RandomAccess, Serializable {
346 final boolean[] array;
347 final int start;
348 final int end;
349
350 BooleanArrayAsList(boolean[] array) {
351 this(array, 0, array.length);
352 }
353
354 BooleanArrayAsList(boolean[] array, int start, int end) {
355 this.array = array;
356 this.start = start;
357 this.end = end;
358 }
359
360 @Override public int size() {
361 return end - start;
362 }
363
364 @Override public boolean isEmpty() {
365 return false;
366 }
367
368 @Override public Boolean get(int index) {
369 checkElementIndex(index, size());
370 return array[start + index];
371 }
372
373 @Override public boolean contains(Object target) {
374 // Overridden to prevent a ton of boxing
375 return (target instanceof Boolean)
376 && Booleans.indexOf(array, (Boolean) target, start, end) != -1;
377 }
378
379 @Override public int indexOf(Object target) {
380 // Overridden to prevent a ton of boxing
381 if (target instanceof Boolean) {
382 int i = Booleans.indexOf(array, (Boolean) target, start, end);
383 if (i >= 0) {
384 return i - start;
385 }
386 }
387 return -1;
388 }
389
390 @Override public int lastIndexOf(Object target) {
391 // Overridden to prevent a ton of boxing
392 if (target instanceof Boolean) {
393 int i = Booleans.lastIndexOf(array, (Boolean) target, start, end);
394 if (i >= 0) {
395 return i - start;
396 }
397 }
398 return -1;
399 }
400
401 @Override public Boolean set(int index, Boolean element) {
402 checkElementIndex(index, size());
403 boolean oldValue = array[start + index];
404 array[start + index] = element;
405 return oldValue;
406 }
407
408 /** In GWT, List and AbstractList do not have the subList method. */
409 @Override public List<Boolean> subList(int fromIndex, int toIndex) {
410 int size = size();
411 checkPositionIndexes(fromIndex, toIndex, size);
412 if (fromIndex == toIndex) {
413 return Collections.emptyList();
414 }
415 return new BooleanArrayAsList(array, start + fromIndex, start + toIndex);
416 }
417
418 @Override public boolean equals(Object object) {
419 if (object == this) {
420 return true;
421 }
422 if (object instanceof BooleanArrayAsList) {
423 BooleanArrayAsList that = (BooleanArrayAsList) object;
424 int size = size();
425 if (that.size() != size) {
426 return false;
427 }
428 for (int i = 0; i < size; i++) {
429 if (array[start + i] != that.array[that.start + i]) {
430 return false;
431 }
432 }
433 return true;
434 }
435 return super.equals(object);
436 }
437
438 @Override public int hashCode() {
439 int result = 1;
440 for (int i = start; i < end; i++) {
441 result = 31 * result + Booleans.hashCode(array[i]);
442 }
443 return result;
444 }
445
446 @Override public String toString() {
447 StringBuilder builder = new StringBuilder(size() * 7);
448 builder.append(array[start] ? "[true" : "[false");
449 for (int i = start + 1; i < end; i++) {
450 builder.append(array[i] ? ", true" : ", false");
451 }
452 return builder.append(']').toString();
453 }
454
455 boolean[] toBooleanArray() {
456 // Arrays.copyOfRange() requires Java 6
457 int size = size();
458 boolean[] result = new boolean[size];
459 System.arraycopy(array, start, result, 0, size);
460 return result;
461 }
462
463 private static final long serialVersionUID = 0;
464 }
465 }