001/* 002 * Copyright (C) 2008 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkArgument; 018import static com.google.common.base.Preconditions.checkElementIndex; 019import static com.google.common.base.Preconditions.checkNotNull; 020import static com.google.common.base.Preconditions.checkPositionIndexes; 021 022import com.google.common.annotations.Beta; 023import com.google.common.annotations.GwtCompatible; 024import java.io.Serializable; 025import java.util.AbstractList; 026import java.util.Arrays; 027import java.util.Collection; 028import java.util.Collections; 029import java.util.Comparator; 030import java.util.List; 031import java.util.RandomAccess; 032import javax.annotation.CheckForNull; 033 034/** 035 * Static utility methods pertaining to {@code boolean} primitives, that are not already found in 036 * either {@link Boolean} or {@link Arrays}. 037 * 038 * <p>See the Guava User Guide article on <a 039 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 040 * 041 * @author Kevin Bourrillion 042 * @since 1.0 043 */ 044@GwtCompatible 045@ElementTypesAreNonnullByDefault 046public final class Booleans { 047 private Booleans() {} 048 049 /** Comparators for {@code Boolean} values. */ 050 private enum BooleanComparator implements Comparator<Boolean> { 051 TRUE_FIRST(1, "Booleans.trueFirst()"), 052 FALSE_FIRST(-1, "Booleans.falseFirst()"); 053 054 private final int trueValue; 055 private final String toString; 056 057 BooleanComparator(int trueValue, String toString) { 058 this.trueValue = trueValue; 059 this.toString = toString; 060 } 061 062 @Override 063 public int compare(Boolean a, Boolean b) { 064 int aVal = a ? trueValue : 0; 065 int bVal = b ? trueValue : 0; 066 return bVal - aVal; 067 } 068 069 @Override 070 public String toString() { 071 return toString; 072 } 073 } 074 075 /** 076 * Returns a {@code Comparator<Boolean>} that sorts {@code true} before {@code false}. 077 * 078 * <p>This is particularly useful in Java 8+ in combination with {@code Comparators.comparing}, 079 * e.g. {@code Comparators.comparing(Foo::hasBar, trueFirst())}. 080 * 081 * @since 21.0 082 */ 083 @Beta 084 public static Comparator<Boolean> trueFirst() { 085 return BooleanComparator.TRUE_FIRST; 086 } 087 088 /** 089 * Returns a {@code Comparator<Boolean>} that sorts {@code false} before {@code true}. 090 * 091 * <p>This is particularly useful in Java 8+ in combination with {@code Comparators.comparing}, 092 * e.g. {@code Comparators.comparing(Foo::hasBar, falseFirst())}. 093 * 094 * @since 21.0 095 */ 096 @Beta 097 public static Comparator<Boolean> falseFirst() { 098 return BooleanComparator.FALSE_FIRST; 099 } 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>There are at most two distinct objects in this list, {@code (Boolean) true} and {@code 365 * (Boolean) false}. Java guarantees that those are always represented by the same objects. 366 * 367 * <p>The returned list is serializable. 368 * 369 * @param backingArray the array to back the list 370 * @return a list view of the array 371 */ 372 public static List<Boolean> asList(boolean... backingArray) { 373 if (backingArray.length == 0) { 374 return Collections.emptyList(); 375 } 376 return new BooleanArrayAsList(backingArray); 377 } 378 379 @GwtCompatible 380 private static class BooleanArrayAsList extends AbstractList<Boolean> 381 implements RandomAccess, Serializable { 382 final boolean[] array; 383 final int start; 384 final int end; 385 386 BooleanArrayAsList(boolean[] array) { 387 this(array, 0, array.length); 388 } 389 390 BooleanArrayAsList(boolean[] array, int start, int end) { 391 this.array = array; 392 this.start = start; 393 this.end = end; 394 } 395 396 @Override 397 public int size() { 398 return end - start; 399 } 400 401 @Override 402 public boolean isEmpty() { 403 return false; 404 } 405 406 @Override 407 public Boolean get(int index) { 408 checkElementIndex(index, size()); 409 return array[start + index]; 410 } 411 412 @Override 413 public boolean contains(@CheckForNull Object target) { 414 // Overridden to prevent a ton of boxing 415 return (target instanceof Boolean) 416 && Booleans.indexOf(array, (Boolean) target, start, end) != -1; 417 } 418 419 @Override 420 public int indexOf(@CheckForNull Object target) { 421 // Overridden to prevent a ton of boxing 422 if (target instanceof Boolean) { 423 int i = Booleans.indexOf(array, (Boolean) target, start, end); 424 if (i >= 0) { 425 return i - start; 426 } 427 } 428 return -1; 429 } 430 431 @Override 432 public int lastIndexOf(@CheckForNull Object target) { 433 // Overridden to prevent a ton of boxing 434 if (target instanceof Boolean) { 435 int i = Booleans.lastIndexOf(array, (Boolean) target, start, end); 436 if (i >= 0) { 437 return i - start; 438 } 439 } 440 return -1; 441 } 442 443 @Override 444 public Boolean set(int index, Boolean element) { 445 checkElementIndex(index, size()); 446 boolean oldValue = array[start + index]; 447 // checkNotNull for GWT (do not optimize) 448 array[start + index] = checkNotNull(element); 449 return oldValue; 450 } 451 452 @Override 453 public List<Boolean> subList(int fromIndex, int toIndex) { 454 int size = size(); 455 checkPositionIndexes(fromIndex, toIndex, size); 456 if (fromIndex == toIndex) { 457 return Collections.emptyList(); 458 } 459 return new BooleanArrayAsList(array, start + fromIndex, start + toIndex); 460 } 461 462 @Override 463 public boolean equals(@CheckForNull Object object) { 464 if (object == this) { 465 return true; 466 } 467 if (object instanceof BooleanArrayAsList) { 468 BooleanArrayAsList that = (BooleanArrayAsList) object; 469 int size = size(); 470 if (that.size() != size) { 471 return false; 472 } 473 for (int i = 0; i < size; i++) { 474 if (array[start + i] != that.array[that.start + i]) { 475 return false; 476 } 477 } 478 return true; 479 } 480 return super.equals(object); 481 } 482 483 @Override 484 public int hashCode() { 485 int result = 1; 486 for (int i = start; i < end; i++) { 487 result = 31 * result + Booleans.hashCode(array[i]); 488 } 489 return result; 490 } 491 492 @Override 493 public String toString() { 494 StringBuilder builder = new StringBuilder(size() * 7); 495 builder.append(array[start] ? "[true" : "[false"); 496 for (int i = start + 1; i < end; i++) { 497 builder.append(array[i] ? ", true" : ", false"); 498 } 499 return builder.append(']').toString(); 500 } 501 502 boolean[] toBooleanArray() { 503 return Arrays.copyOfRange(array, start, end); 504 } 505 506 private static final long serialVersionUID = 0; 507 } 508 509 /** 510 * Returns the number of {@code values} that are {@code true}. 511 * 512 * @since 16.0 513 */ 514 @Beta 515 public static int countTrue(boolean... values) { 516 int count = 0; 517 for (boolean value : values) { 518 if (value) { 519 count++; 520 } 521 } 522 return count; 523 } 524 525 /** 526 * Reverses the elements of {@code array}. This is equivalent to {@code 527 * Collections.reverse(Booleans.asList(array))}, but is likely to be more efficient. 528 * 529 * @since 23.1 530 */ 531 public static void reverse(boolean[] array) { 532 checkNotNull(array); 533 reverse(array, 0, array.length); 534 } 535 536 /** 537 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 538 * exclusive. This is equivalent to {@code 539 * Collections.reverse(Booleans.asList(array).subList(fromIndex, toIndex))}, but is likely to be 540 * more efficient. 541 * 542 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 543 * {@code toIndex > fromIndex} 544 * @since 23.1 545 */ 546 public static void reverse(boolean[] array, int fromIndex, int toIndex) { 547 checkNotNull(array); 548 checkPositionIndexes(fromIndex, toIndex, array.length); 549 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 550 boolean tmp = array[i]; 551 array[i] = array[j]; 552 array[j] = tmp; 553 } 554 } 555 556 /** 557 * Performs a right rotation of {@code array} of "distance" places, so that the first element is 558 * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance 559 * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Booleans.asList(array), 560 * distance)}, but is somewhat faster. 561 * 562 * <p>The provided "distance" may be negative, which will rotate left. 563 * 564 * @since NEXT 565 */ 566 public static void rotate(boolean[] array, int distance) { 567 rotate(array, distance, 0, array.length); 568 } 569 570 /** 571 * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code 572 * toIndex} exclusive. This is equivalent to {@code 573 * Collections.rotate(Booleans.asList(array).subList(fromIndex, toIndex), distance)}, but is 574 * somewhat faster. 575 * 576 * <p>The provided "distance" may be negative, which will rotate left. 577 * 578 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 579 * {@code toIndex > fromIndex} 580 * @since NEXT 581 */ 582 public static void rotate(boolean[] array, int distance, int fromIndex, int toIndex) { 583 // See Ints.rotate for more details about possible algorithms here. 584 checkNotNull(array); 585 checkPositionIndexes(fromIndex, toIndex, array.length); 586 if (array.length <= 1) { 587 return; 588 } 589 590 int length = toIndex - fromIndex; 591 // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many 592 // places left to rotate. 593 int m = -distance % length; 594 m = (m < 0) ? m + length : m; 595 // The current index of what will become the first element of the rotated section. 596 int newFirstIndex = m + fromIndex; 597 if (newFirstIndex == fromIndex) { 598 return; 599 } 600 601 reverse(array, fromIndex, newFirstIndex); 602 reverse(array, newFirstIndex, toIndex); 603 reverse(array, fromIndex, toIndex); 604 } 605}