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 com.google.common.base.Converter; 025import java.io.Serializable; 026import java.util.AbstractList; 027import java.util.Arrays; 028import java.util.Collection; 029import java.util.Collections; 030import java.util.Comparator; 031import java.util.List; 032import java.util.RandomAccess; 033import javax.annotation.CheckForNull; 034import javax.annotation.Nullable; 035 036/** 037 * Static utility methods pertaining to {@code int} primitives, that are not already found in either 038 * {@link Integer} or {@link Arrays}. 039 * 040 * <p>See the Guava User Guide article on 041 * <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 042 * 043 * @author Kevin Bourrillion 044 * @since 1.0 045 */ 046@GwtCompatible 047public final class Ints { 048 private Ints() {} 049 050 /** 051 * The number of bytes required to represent a primitive {@code int} value. 052 * 053 * <p><b>Java 8 users:</b> use {@link Integer#BYTES} instead. 054 */ 055 public static final int BYTES = Integer.SIZE / Byte.SIZE; 056 057 /** 058 * The largest power of two that can be represented as an {@code int}. 059 * 060 * @since 10.0 061 */ 062 public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2); 063 064 /** 065 * Returns a hash code for {@code value}; equal to the result of invoking 066 * {@code ((Integer) value).hashCode()}. 067 * 068 * <p><b>Java 8 users:</b> use {@link Integer#hashCode(int)} instead. 069 * 070 * @param value a primitive {@code int} value 071 * @return a hash code for the value 072 */ 073 public static int hashCode(int value) { 074 return value; 075 } 076 077 /** 078 * Returns the {@code int} value that is equal to {@code value}, if possible. 079 * 080 * @param value any value in the range of the {@code int} type 081 * @return the {@code int} value that equals {@code value} 082 * @throws IllegalArgumentException if {@code value} is greater than {@link Integer#MAX_VALUE} or 083 * less than {@link Integer#MIN_VALUE} 084 */ 085 public static int checkedCast(long value) { 086 int result = (int) value; 087 checkArgument(result == value, "Out of range: %s", value); 088 return result; 089 } 090 091 /** 092 * Returns the {@code int} nearest in value to {@code value}. 093 * 094 * @param value any {@code long} value 095 * @return the same value cast to {@code int} if it is in the range of the {@code int} type, 096 * {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too 097 * small 098 */ 099 public static int saturatedCast(long value) { 100 if (value > Integer.MAX_VALUE) { 101 return Integer.MAX_VALUE; 102 } 103 if (value < Integer.MIN_VALUE) { 104 return Integer.MIN_VALUE; 105 } 106 return (int) value; 107 } 108 109 /** 110 * Compares the two specified {@code int} values. The sign of the value returned is the same as 111 * that of {@code ((Integer) a).compareTo(b)}. 112 * 113 * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the 114 * equivalent {@link Integer#compare} method instead. 115 * 116 * @param a the first {@code int} to compare 117 * @param b the second {@code int} to compare 118 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 119 * greater than {@code b}; or zero if they are equal 120 */ 121 public static int compare(int a, int b) { 122 return (a < b) ? -1 : ((a > b) ? 1 : 0); 123 } 124 125 /** 126 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. 127 * 128 * @param array an array of {@code int} values, possibly empty 129 * @param target a primitive {@code int} value 130 * @return {@code true} if {@code array[i] == target} for some value of {@code 131 * i} 132 */ 133 public static boolean contains(int[] array, int target) { 134 for (int value : array) { 135 if (value == target) { 136 return true; 137 } 138 } 139 return false; 140 } 141 142 /** 143 * Returns the index of the first appearance of the value {@code target} in {@code array}. 144 * 145 * @param array an array of {@code int} values, possibly empty 146 * @param target a primitive {@code int} value 147 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 148 * such index exists. 149 */ 150 public static int indexOf(int[] array, int target) { 151 return indexOf(array, target, 0, array.length); 152 } 153 154 // TODO(kevinb): consider making this public 155 private static int indexOf(int[] array, int target, int start, int end) { 156 for (int i = start; i < end; i++) { 157 if (array[i] == target) { 158 return i; 159 } 160 } 161 return -1; 162 } 163 164 /** 165 * Returns the start position of the first occurrence of the specified {@code 166 * target} within {@code array}, or {@code -1} if there is no such occurrence. 167 * 168 * <p>More formally, returns the lowest index {@code i} such that 169 * {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as 170 * {@code target}. 171 * 172 * @param array the array to search for the sequence {@code target} 173 * @param target the array to search for as a sub-sequence of {@code array} 174 */ 175 public static int indexOf(int[] array, int[] target) { 176 checkNotNull(array, "array"); 177 checkNotNull(target, "target"); 178 if (target.length == 0) { 179 return 0; 180 } 181 182 outer: 183 for (int i = 0; i < array.length - target.length + 1; i++) { 184 for (int j = 0; j < target.length; j++) { 185 if (array[i + j] != target[j]) { 186 continue outer; 187 } 188 } 189 return i; 190 } 191 return -1; 192 } 193 194 /** 195 * Returns the index of the last appearance of the value {@code target} in {@code array}. 196 * 197 * @param array an array of {@code int} values, possibly empty 198 * @param target a primitive {@code int} value 199 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 200 * such index exists. 201 */ 202 public static int lastIndexOf(int[] array, int target) { 203 return lastIndexOf(array, target, 0, array.length); 204 } 205 206 // TODO(kevinb): consider making this public 207 private static int lastIndexOf(int[] array, int target, int start, int end) { 208 for (int i = end - 1; i >= start; i--) { 209 if (array[i] == target) { 210 return i; 211 } 212 } 213 return -1; 214 } 215 216 /** 217 * Returns the least value present in {@code array}. 218 * 219 * @param array a <i>nonempty</i> array of {@code int} values 220 * @return the value present in {@code array} that is less than or equal to every other value in 221 * the array 222 * @throws IllegalArgumentException if {@code array} is empty 223 */ 224 public static int min(int... array) { 225 checkArgument(array.length > 0); 226 int min = array[0]; 227 for (int i = 1; i < array.length; i++) { 228 if (array[i] < min) { 229 min = array[i]; 230 } 231 } 232 return min; 233 } 234 235 /** 236 * Returns the greatest value present in {@code array}. 237 * 238 * @param array a <i>nonempty</i> array of {@code int} values 239 * @return the value present in {@code array} that is greater than or equal to every other value 240 * in the array 241 * @throws IllegalArgumentException if {@code array} is empty 242 */ 243 public static int max(int... array) { 244 checkArgument(array.length > 0); 245 int max = array[0]; 246 for (int i = 1; i < array.length; i++) { 247 if (array[i] > max) { 248 max = array[i]; 249 } 250 } 251 return max; 252 } 253 254 /** 255 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 256 * 257 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 258 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if 259 * {@code value} is greater than {@code max}, {@code max} is returned. 260 * 261 * @param value the {@code int} value to constrain 262 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 263 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 264 * @throws IllegalArgumentException if {@code min > max} 265 * @since 21.0 266 */ 267 @Beta 268 public static int constrainToRange(int value, int min, int max) { 269 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 270 return Math.min(Math.max(value, min), max); 271 } 272 273 /** 274 * Returns the values from each provided array combined into a single array. For example, 275 * {@code concat(new int[] {a, b}, new int[] {}, new int[] {c}} returns the array {@code {a, b, 276 * c}}. 277 * 278 * @param arrays zero or more {@code int} arrays 279 * @return a single array containing all the values from the source arrays, in order 280 */ 281 public static int[] concat(int[]... arrays) { 282 int length = 0; 283 for (int[] array : arrays) { 284 length += array.length; 285 } 286 int[] result = new int[length]; 287 int pos = 0; 288 for (int[] array : arrays) { 289 System.arraycopy(array, 0, result, pos, array.length); 290 pos += array.length; 291 } 292 return result; 293 } 294 295 /** 296 * Returns a big-endian representation of {@code value} in a 4-element byte array; equivalent to 297 * {@code ByteBuffer.allocate(4).putInt(value).array()}. For example, the input value 298 * {@code 0x12131415} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15}}. 299 * 300 * <p>If you need to convert and concatenate several values (possibly even of different types), 301 * use a shared {@link java.nio.ByteBuffer} instance, or use 302 * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer. 303 */ 304 public static byte[] toByteArray(int value) { 305 return new byte[] { 306 (byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) value 307 }; 308 } 309 310 /** 311 * Returns the {@code int} value whose big-endian representation is stored in the first 4 bytes of 312 * {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getInt()}. For example, the input 313 * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value 314 * {@code 0x12131415}. 315 * 316 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more 317 * flexibility at little cost in readability. 318 * 319 * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements 320 */ 321 public static int fromByteArray(byte[] bytes) { 322 checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES); 323 return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]); 324 } 325 326 /** 327 * Returns the {@code int} value whose byte representation is the given 4 bytes, in big-endian 328 * order; equivalent to {@code Ints.fromByteArray(new byte[] {b1, b2, b3, b4})}. 329 * 330 * @since 7.0 331 */ 332 public static int fromBytes(byte b1, byte b2, byte b3, byte b4) { 333 return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF); 334 } 335 336 private static final class IntConverter extends Converter<String, Integer> 337 implements Serializable { 338 static final IntConverter INSTANCE = new IntConverter(); 339 340 @Override 341 protected Integer doForward(String value) { 342 return Integer.decode(value); 343 } 344 345 @Override 346 protected String doBackward(Integer value) { 347 return value.toString(); 348 } 349 350 @Override 351 public String toString() { 352 return "Ints.stringConverter()"; 353 } 354 355 private Object readResolve() { 356 return INSTANCE; 357 } 358 359 private static final long serialVersionUID = 1; 360 } 361 362 /** 363 * Returns a serializable converter object that converts between strings and integers using 364 * {@link Integer#decode} and {@link Integer#toString()}. The returned converter throws 365 * {@link NumberFormatException} if the input string is invalid. 366 * 367 * <p><b>Warning:</b> please see {@link Integer#decode} to understand exactly how strings are 368 * parsed. For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the 369 * value {@code 83}. 370 * 371 * @since 16.0 372 */ 373 @Beta 374 public static Converter<String, Integer> stringConverter() { 375 return IntConverter.INSTANCE; 376 } 377 378 /** 379 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 380 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 381 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 382 * returned, containing the values of {@code array}, and zeroes in the remaining places. 383 * 384 * @param array the source array 385 * @param minLength the minimum length the returned array must guarantee 386 * @param padding an extra amount to "grow" the array by if growth is necessary 387 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 388 * @return an array containing the values of {@code array}, with guaranteed minimum length 389 * {@code minLength} 390 */ 391 public static int[] ensureCapacity(int[] array, int minLength, int padding) { 392 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 393 checkArgument(padding >= 0, "Invalid padding: %s", padding); 394 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 395 } 396 397 /** 398 * Returns a string containing the supplied {@code int} values separated by {@code separator}. For 399 * example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}. 400 * 401 * @param separator the text that should appear between consecutive values in the resulting string 402 * (but not at the start or end) 403 * @param array an array of {@code int} values, possibly empty 404 */ 405 public static String join(String separator, int... array) { 406 checkNotNull(separator); 407 if (array.length == 0) { 408 return ""; 409 } 410 411 // For pre-sizing a builder, just get the right order of magnitude 412 StringBuilder builder = new StringBuilder(array.length * 5); 413 builder.append(array[0]); 414 for (int i = 1; i < array.length; i++) { 415 builder.append(separator).append(array[i]); 416 } 417 return builder.toString(); 418 } 419 420 /** 421 * Returns a comparator that compares two {@code int} arrays <a 422 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 423 * compares, using {@link #compare(int, int)}), the first pair of values that follow any common 424 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 425 * example, {@code [] < [1] < [1, 2] < [2]}. 426 * 427 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 428 * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}. 429 * 430 * @since 2.0 431 */ 432 public static Comparator<int[]> lexicographicalComparator() { 433 return LexicographicalComparator.INSTANCE; 434 } 435 436 private enum LexicographicalComparator implements Comparator<int[]> { 437 INSTANCE; 438 439 @Override 440 public int compare(int[] left, int[] right) { 441 int minLength = Math.min(left.length, right.length); 442 for (int i = 0; i < minLength; i++) { 443 int result = Ints.compare(left[i], right[i]); 444 if (result != 0) { 445 return result; 446 } 447 } 448 return left.length - right.length; 449 } 450 451 @Override 452 public String toString() { 453 return "Ints.lexicographicalComparator()"; 454 } 455 } 456 457 /** 458 * Returns an array containing each value of {@code collection}, converted to a {@code int} value 459 * in the manner of {@link Number#intValue}. 460 * 461 * <p>Elements are copied from the argument collection as if by {@code 462 * collection.toArray()}. Calling this method is as thread-safe as calling that method. 463 * 464 * @param collection a collection of {@code Number} instances 465 * @return an array containing the same values as {@code collection}, in the same order, converted 466 * to primitives 467 * @throws NullPointerException if {@code collection} or any of its elements is null 468 * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0) 469 */ 470 public static int[] toArray(Collection<? extends Number> collection) { 471 if (collection instanceof IntArrayAsList) { 472 return ((IntArrayAsList) collection).toIntArray(); 473 } 474 475 Object[] boxedArray = collection.toArray(); 476 int len = boxedArray.length; 477 int[] array = new int[len]; 478 for (int i = 0; i < len; i++) { 479 // checkNotNull for GWT (do not optimize) 480 array[i] = ((Number) checkNotNull(boxedArray[i])).intValue(); 481 } 482 return array; 483 } 484 485 /** 486 * Returns a fixed-size list backed by the specified array, similar to 487 * {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any 488 * attempt to set a value to {@code null} will result in a {@link NullPointerException}. 489 * 490 * <p>The returned list maintains the values, but not the identities, of {@code Integer} objects 491 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 492 * the returned list is unspecified. 493 * 494 * @param backingArray the array to back the list 495 * @return a list view of the array 496 */ 497 public static List<Integer> asList(int... backingArray) { 498 if (backingArray.length == 0) { 499 return Collections.emptyList(); 500 } 501 return new IntArrayAsList(backingArray); 502 } 503 504 @GwtCompatible 505 private static class IntArrayAsList extends AbstractList<Integer> 506 implements RandomAccess, Serializable { 507 final int[] array; 508 final int start; 509 final int end; 510 511 IntArrayAsList(int[] array) { 512 this(array, 0, array.length); 513 } 514 515 IntArrayAsList(int[] array, int start, int end) { 516 this.array = array; 517 this.start = start; 518 this.end = end; 519 } 520 521 @Override 522 public int size() { 523 return end - start; 524 } 525 526 @Override 527 public boolean isEmpty() { 528 return false; 529 } 530 531 @Override 532 public Integer get(int index) { 533 checkElementIndex(index, size()); 534 return array[start + index]; 535 } 536 537 @Override 538 public boolean contains(Object target) { 539 // Overridden to prevent a ton of boxing 540 return (target instanceof Integer) && Ints.indexOf(array, (Integer) target, start, end) != -1; 541 } 542 543 @Override 544 public int indexOf(Object target) { 545 // Overridden to prevent a ton of boxing 546 if (target instanceof Integer) { 547 int i = Ints.indexOf(array, (Integer) target, start, end); 548 if (i >= 0) { 549 return i - start; 550 } 551 } 552 return -1; 553 } 554 555 @Override 556 public int lastIndexOf(Object target) { 557 // Overridden to prevent a ton of boxing 558 if (target instanceof Integer) { 559 int i = Ints.lastIndexOf(array, (Integer) target, start, end); 560 if (i >= 0) { 561 return i - start; 562 } 563 } 564 return -1; 565 } 566 567 @Override 568 public Integer set(int index, Integer element) { 569 checkElementIndex(index, size()); 570 int oldValue = array[start + index]; 571 // checkNotNull for GWT (do not optimize) 572 array[start + index] = checkNotNull(element); 573 return oldValue; 574 } 575 576 @Override 577 public List<Integer> subList(int fromIndex, int toIndex) { 578 int size = size(); 579 checkPositionIndexes(fromIndex, toIndex, size); 580 if (fromIndex == toIndex) { 581 return Collections.emptyList(); 582 } 583 return new IntArrayAsList(array, start + fromIndex, start + toIndex); 584 } 585 586 @Override 587 public boolean equals(@Nullable Object object) { 588 if (object == this) { 589 return true; 590 } 591 if (object instanceof IntArrayAsList) { 592 IntArrayAsList that = (IntArrayAsList) object; 593 int size = size(); 594 if (that.size() != size) { 595 return false; 596 } 597 for (int i = 0; i < size; i++) { 598 if (array[start + i] != that.array[that.start + i]) { 599 return false; 600 } 601 } 602 return true; 603 } 604 return super.equals(object); 605 } 606 607 @Override 608 public int hashCode() { 609 int result = 1; 610 for (int i = start; i < end; i++) { 611 result = 31 * result + Ints.hashCode(array[i]); 612 } 613 return result; 614 } 615 616 @Override 617 public String toString() { 618 StringBuilder builder = new StringBuilder(size() * 5); 619 builder.append('[').append(array[start]); 620 for (int i = start + 1; i < end; i++) { 621 builder.append(", ").append(array[i]); 622 } 623 return builder.append(']').toString(); 624 } 625 626 int[] toIntArray() { 627 return Arrays.copyOfRange(array, start, end); 628 } 629 630 private static final long serialVersionUID = 0; 631 } 632 633 /** 634 * Parses the specified string as a signed decimal integer value. The ASCII character {@code '-'} 635 * (<code>'\u002D'</code>) is recognized as the minus sign. 636 * 637 * <p>Unlike {@link Integer#parseInt(String)}, this method returns {@code null} instead of 638 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 639 * and returns {@code null} if non-ASCII digits are present in the string. 640 * 641 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 642 * the change to {@link Integer#parseInt(String)} for that version. 643 * 644 * @param string the string representation of an integer value 645 * @return the integer value represented by {@code string}, or {@code null} if {@code string} has 646 * a length of zero or cannot be parsed as an integer value 647 * @since 11.0 648 */ 649 @Beta 650 @Nullable 651 @CheckForNull 652 public static Integer tryParse(String string) { 653 return tryParse(string, 10); 654 } 655 656 /** 657 * Parses the specified string as a signed integer value using the specified radix. The ASCII 658 * character {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 659 * 660 * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns {@code null} instead of 661 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 662 * and returns {@code null} if non-ASCII digits are present in the string. 663 * 664 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 665 * the change to {@link Integer#parseInt(String, int)} for that version. 666 * 667 * @param string the string representation of an integer value 668 * @param radix the radix to use when parsing 669 * @return the integer value represented by {@code string} using {@code radix}, or {@code null} if 670 * {@code string} has a length of zero or cannot be parsed as an integer value 671 * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or 672 * {@code radix > Character.MAX_RADIX} 673 * @since 19.0 674 */ 675 @Beta 676 @Nullable 677 @CheckForNull 678 public static Integer tryParse(String string, int radix) { 679 Long result = Longs.tryParse(string, radix); 680 if (result == null || result.longValue() != result.intValue()) { 681 return null; 682 } else { 683 return result.intValue(); 684 } 685 } 686}