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.GwtCompatible; 023import com.google.common.annotations.GwtIncompatible; 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; 034 035/** 036 * Static utility methods pertaining to {@code int} primitives, that are not already found in either 037 * {@link Integer} or {@link Arrays}. 038 * 039 * <p>See the Guava User Guide article on <a 040 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>. 041 * 042 * @author Kevin Bourrillion 043 * @since 1.0 044 */ 045@GwtCompatible(emulated = true) 046@ElementTypesAreNonnullByDefault 047public final class Ints extends IntsMethodsForWeb { 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 {@code ((Integer) 066 * 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 i} 131 */ 132 public static boolean contains(int[] array, int target) { 133 for (int value : array) { 134 if (value == target) { 135 return true; 136 } 137 } 138 return false; 139 } 140 141 /** 142 * Returns the index of the first appearance of the value {@code target} in {@code array}. 143 * 144 * @param array an array of {@code int} values, possibly empty 145 * @param target a primitive {@code int} value 146 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 147 * such index exists. 148 */ 149 public static int indexOf(int[] array, int target) { 150 return indexOf(array, target, 0, array.length); 151 } 152 153 // TODO(kevinb): consider making this public 154 private static int indexOf(int[] array, int target, int start, int end) { 155 for (int i = start; i < end; i++) { 156 if (array[i] == target) { 157 return i; 158 } 159 } 160 return -1; 161 } 162 163 /** 164 * Returns the start position of the first occurrence of the specified {@code target} within 165 * {@code array}, or {@code -1} if there is no such occurrence. 166 * 167 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 168 * i, i + target.length)} contains exactly the same elements as {@code target}. 169 * 170 * @param array the array to search for the sequence {@code target} 171 * @param target the array to search for as a sub-sequence of {@code array} 172 */ 173 public static int indexOf(int[] array, int[] target) { 174 checkNotNull(array, "array"); 175 checkNotNull(target, "target"); 176 if (target.length == 0) { 177 return 0; 178 } 179 180 outer: 181 for (int i = 0; i < array.length - target.length + 1; i++) { 182 for (int j = 0; j < target.length; j++) { 183 if (array[i + j] != target[j]) { 184 continue outer; 185 } 186 } 187 return i; 188 } 189 return -1; 190 } 191 192 /** 193 * Returns the index of the last appearance of the value {@code target} in {@code array}. 194 * 195 * @param array an array of {@code int} values, possibly empty 196 * @param target a primitive {@code int} value 197 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 198 * such index exists. 199 */ 200 public static int lastIndexOf(int[] array, int target) { 201 return lastIndexOf(array, target, 0, array.length); 202 } 203 204 // TODO(kevinb): consider making this public 205 private static int lastIndexOf(int[] array, int target, int start, int end) { 206 for (int i = end - 1; i >= start; i--) { 207 if (array[i] == target) { 208 return i; 209 } 210 } 211 return -1; 212 } 213 214 /** 215 * Returns the least value present in {@code array}. 216 * 217 * @param array a <i>nonempty</i> array of {@code int} values 218 * @return the value present in {@code array} that is less than or equal to every other value in 219 * the array 220 * @throws IllegalArgumentException if {@code array} is empty 221 */ 222 @GwtIncompatible( 223 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.") 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 @GwtIncompatible( 244 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.") 245 public static int max(int... array) { 246 checkArgument(array.length > 0); 247 int max = array[0]; 248 for (int i = 1; i < array.length; i++) { 249 if (array[i] > max) { 250 max = array[i]; 251 } 252 } 253 return max; 254 } 255 256 /** 257 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 258 * 259 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 260 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 261 * value} is greater than {@code max}, {@code max} is returned. 262 * 263 * @param value the {@code int} value to constrain 264 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 265 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 266 * @throws IllegalArgumentException if {@code min > max} 267 * @since 21.0 268 */ 269 public static int constrainToRange(int value, int min, int max) { 270 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 271 return Math.min(Math.max(value, min), max); 272 } 273 274 /** 275 * Returns the values from each provided array combined into a single array. For example, {@code 276 * concat(new int[] {a, b}, new int[] {}, new int[] {c}} returns the array {@code {a, b, 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 {@code 298 * 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 {@link 302 * 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 {@code 314 * 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 {@link 364 * Integer#decode} and {@link Integer#toString()}. The returned converter throws {@link 365 * 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 public static Converter<String, Integer> stringConverter() { 374 return IntConverter.INSTANCE; 375 } 376 377 /** 378 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 379 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 380 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 381 * returned, containing the values of {@code array}, and zeroes in the remaining places. 382 * 383 * @param array the source array 384 * @param minLength the minimum length the returned array must guarantee 385 * @param padding an extra amount to "grow" the array by if growth is necessary 386 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 387 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 388 * minLength} 389 */ 390 public static int[] ensureCapacity(int[] array, int minLength, int padding) { 391 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 392 checkArgument(padding >= 0, "Invalid padding: %s", padding); 393 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 394 } 395 396 /** 397 * Returns a string containing the supplied {@code int} values separated by {@code separator}. For 398 * example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}. 399 * 400 * @param separator the text that should appear between consecutive values in the resulting string 401 * (but not at the start or end) 402 * @param array an array of {@code int} values, possibly empty 403 */ 404 public static String join(String separator, int... array) { 405 checkNotNull(separator); 406 if (array.length == 0) { 407 return ""; 408 } 409 410 // For pre-sizing a builder, just get the right order of magnitude 411 StringBuilder builder = new StringBuilder(array.length * 5); 412 builder.append(array[0]); 413 for (int i = 1; i < array.length; i++) { 414 builder.append(separator).append(array[i]); 415 } 416 return builder.toString(); 417 } 418 419 /** 420 * Returns a comparator that compares two {@code int} arrays <a 421 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 422 * compares, using {@link #compare(int, int)}), the first pair of values that follow any common 423 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 424 * example, {@code [] < [1] < [1, 2] < [2]}. 425 * 426 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 427 * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}. 428 * 429 * @since 2.0 430 */ 431 public static Comparator<int[]> lexicographicalComparator() { 432 return LexicographicalComparator.INSTANCE; 433 } 434 435 private enum LexicographicalComparator implements Comparator<int[]> { 436 INSTANCE; 437 438 @Override 439 public int compare(int[] left, int[] right) { 440 int minLength = Math.min(left.length, right.length); 441 for (int i = 0; i < minLength; i++) { 442 int result = Ints.compare(left[i], right[i]); 443 if (result != 0) { 444 return result; 445 } 446 } 447 return left.length - right.length; 448 } 449 450 @Override 451 public String toString() { 452 return "Ints.lexicographicalComparator()"; 453 } 454 } 455 456 /** 457 * Sorts the elements of {@code array} in descending order. 458 * 459 * @since 23.1 460 */ 461 public static void sortDescending(int[] array) { 462 checkNotNull(array); 463 sortDescending(array, 0, array.length); 464 } 465 466 /** 467 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 468 * exclusive in descending order. 469 * 470 * @since 23.1 471 */ 472 public static void sortDescending(int[] array, int fromIndex, int toIndex) { 473 checkNotNull(array); 474 checkPositionIndexes(fromIndex, toIndex, array.length); 475 Arrays.sort(array, fromIndex, toIndex); 476 reverse(array, fromIndex, toIndex); 477 } 478 479 /** 480 * Reverses the elements of {@code array}. This is equivalent to {@code 481 * Collections.reverse(Ints.asList(array))}, but is likely to be more efficient. 482 * 483 * @since 23.1 484 */ 485 public static void reverse(int[] array) { 486 checkNotNull(array); 487 reverse(array, 0, array.length); 488 } 489 490 /** 491 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 492 * exclusive. This is equivalent to {@code 493 * Collections.reverse(Ints.asList(array).subList(fromIndex, toIndex))}, but is likely to be more 494 * efficient. 495 * 496 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 497 * {@code toIndex > fromIndex} 498 * @since 23.1 499 */ 500 public static void reverse(int[] array, int fromIndex, int toIndex) { 501 checkNotNull(array); 502 checkPositionIndexes(fromIndex, toIndex, array.length); 503 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 504 int tmp = array[i]; 505 array[i] = array[j]; 506 array[j] = tmp; 507 } 508 } 509 510 /** 511 * Performs a right rotation of {@code array} of "distance" places, so that the first element is 512 * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance 513 * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Ints.asList(array), 514 * distance)}, but is considerably faster and avoids allocation and garbage collection. 515 * 516 * <p>The provided "distance" may be negative, which will rotate left. 517 * 518 * @since 32.0.0 519 */ 520 public static void rotate(int[] array, int distance) { 521 rotate(array, distance, 0, array.length); 522 } 523 524 /** 525 * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code 526 * toIndex} exclusive. This is equivalent to {@code 527 * Collections.rotate(Ints.asList(array).subList(fromIndex, toIndex), distance)}, but is 528 * considerably faster and avoids allocations and garbage collection. 529 * 530 * <p>The provided "distance" may be negative, which will rotate left. 531 * 532 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 533 * {@code toIndex > fromIndex} 534 * @since 32.0.0 535 */ 536 public static void rotate(int[] array, int distance, int fromIndex, int toIndex) { 537 // There are several well-known algorithms for rotating part of an array (or, equivalently, 538 // exchanging two blocks of memory). This classic text by Gries and Mills mentions several: 539 // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf. 540 // (1) "Reversal", the one we have here. 541 // (2) "Dolphin". If we're rotating an array a of size n by a distance of d, then element a[0] 542 // ends up at a[d], which in turn ends up at a[2d], and so on until we get back to a[0]. 543 // (All indices taken mod n.) If d and n are mutually prime, all elements will have been 544 // moved at that point. Otherwise, we can rotate the cycle a[1], a[1 + d], a[1 + 2d], etc, 545 // then a[2] etc, and so on until we have rotated all elements. There are gcd(d, n) cycles 546 // in all. 547 // (3) "Successive". We can consider that we are exchanging a block of size d (a[0..d-1]) with a 548 // block of size n-d (a[d..n-1]), where in general these blocks have different sizes. If we 549 // imagine a line separating the first block from the second, we can proceed by exchanging 550 // the smaller of these blocks with the far end of the other one. That leaves us with a 551 // smaller version of the same problem. 552 // Say we are rotating abcdefgh by 5. We start with abcde|fgh. The smaller block is [fgh]: 553 // [abc]de|[fgh] -> [fgh]de|[abc]. Now [fgh] is in the right place, but we need to swap [de] 554 // with [abc]: fgh[de]|a[bc] -> fgh[bc]|a[de]. Now we need to swap [a] with [bc]: 555 // fgh[b]c|[a]de -> fgh[a]c|[b]de. Finally we need to swap [c] with [b]: 556 // fgha[c]|[b]de -> fgha[b]|[c]de. Because these two blocks are the same size, we are done. 557 // The Dolphin algorithm is attractive because it does the fewest array reads and writes: each 558 // array slot is read and written exactly once. However, it can have very poor memory locality: 559 // benchmarking shows it can take 7 times longer than the other two in some cases. The other two 560 // do n swaps, minus a delta (0 or 2 for Reversal, gcd(d, n) for Successive), so that's about 561 // twice as many reads and writes. But benchmarking shows that they usually perform better than 562 // Dolphin. Reversal is about as good as Successive on average, and it is much simpler, 563 // especially since we already have a `reverse` method. 564 checkNotNull(array); 565 checkPositionIndexes(fromIndex, toIndex, array.length); 566 if (array.length <= 1) { 567 return; 568 } 569 570 int length = toIndex - fromIndex; 571 // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many 572 // places left to rotate. 573 int m = -distance % length; 574 m = (m < 0) ? m + length : m; 575 // The current index of what will become the first element of the rotated section. 576 int newFirstIndex = m + fromIndex; 577 if (newFirstIndex == fromIndex) { 578 return; 579 } 580 581 reverse(array, fromIndex, newFirstIndex); 582 reverse(array, newFirstIndex, toIndex); 583 reverse(array, fromIndex, toIndex); 584 } 585 586 /** 587 * Returns an array containing each value of {@code collection}, converted to a {@code int} value 588 * in the manner of {@link Number#intValue}. 589 * 590 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 591 * Calling this method is as thread-safe as calling that method. 592 * 593 * @param collection a collection of {@code Number} instances 594 * @return an array containing the same values as {@code collection}, in the same order, converted 595 * to primitives 596 * @throws NullPointerException if {@code collection} or any of its elements is null 597 * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0) 598 */ 599 public static int[] toArray(Collection<? extends Number> collection) { 600 if (collection instanceof IntArrayAsList) { 601 return ((IntArrayAsList) collection).toIntArray(); 602 } 603 604 Object[] boxedArray = collection.toArray(); 605 int len = boxedArray.length; 606 int[] array = new int[len]; 607 for (int i = 0; i < len; i++) { 608 // checkNotNull for GWT (do not optimize) 609 array[i] = ((Number) checkNotNull(boxedArray[i])).intValue(); 610 } 611 return array; 612 } 613 614 /** 615 * Returns a fixed-size list backed by the specified array, similar to {@link 616 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 617 * set a value to {@code null} will result in a {@link NullPointerException}. 618 * 619 * <p>The returned list maintains the values, but not the identities, of {@code Integer} objects 620 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 621 * the returned list is unspecified. 622 * 623 * <p>The returned list is serializable. 624 * 625 * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableIntArray} 626 * instead, which has an {@link ImmutableIntArray#asList asList} view. 627 * 628 * @param backingArray the array to back the list 629 * @return a list view of the array 630 */ 631 public static List<Integer> asList(int... backingArray) { 632 if (backingArray.length == 0) { 633 return Collections.emptyList(); 634 } 635 return new IntArrayAsList(backingArray); 636 } 637 638 @GwtCompatible 639 private static class IntArrayAsList extends AbstractList<Integer> 640 implements RandomAccess, Serializable { 641 final int[] array; 642 final int start; 643 final int end; 644 645 IntArrayAsList(int[] array) { 646 this(array, 0, array.length); 647 } 648 649 IntArrayAsList(int[] array, int start, int end) { 650 this.array = array; 651 this.start = start; 652 this.end = end; 653 } 654 655 @Override 656 public int size() { 657 return end - start; 658 } 659 660 @Override 661 public boolean isEmpty() { 662 return false; 663 } 664 665 @Override 666 public Integer get(int index) { 667 checkElementIndex(index, size()); 668 return array[start + index]; 669 } 670 671 @Override 672 public boolean contains(@CheckForNull Object target) { 673 // Overridden to prevent a ton of boxing 674 return (target instanceof Integer) && Ints.indexOf(array, (Integer) target, start, end) != -1; 675 } 676 677 @Override 678 public int indexOf(@CheckForNull Object target) { 679 // Overridden to prevent a ton of boxing 680 if (target instanceof Integer) { 681 int i = Ints.indexOf(array, (Integer) target, start, end); 682 if (i >= 0) { 683 return i - start; 684 } 685 } 686 return -1; 687 } 688 689 @Override 690 public int lastIndexOf(@CheckForNull Object target) { 691 // Overridden to prevent a ton of boxing 692 if (target instanceof Integer) { 693 int i = Ints.lastIndexOf(array, (Integer) target, start, end); 694 if (i >= 0) { 695 return i - start; 696 } 697 } 698 return -1; 699 } 700 701 @Override 702 public Integer set(int index, Integer element) { 703 checkElementIndex(index, size()); 704 int oldValue = array[start + index]; 705 // checkNotNull for GWT (do not optimize) 706 array[start + index] = checkNotNull(element); 707 return oldValue; 708 } 709 710 @Override 711 public List<Integer> subList(int fromIndex, int toIndex) { 712 int size = size(); 713 checkPositionIndexes(fromIndex, toIndex, size); 714 if (fromIndex == toIndex) { 715 return Collections.emptyList(); 716 } 717 return new IntArrayAsList(array, start + fromIndex, start + toIndex); 718 } 719 720 @Override 721 public boolean equals(@CheckForNull Object object) { 722 if (object == this) { 723 return true; 724 } 725 if (object instanceof IntArrayAsList) { 726 IntArrayAsList that = (IntArrayAsList) object; 727 int size = size(); 728 if (that.size() != size) { 729 return false; 730 } 731 for (int i = 0; i < size; i++) { 732 if (array[start + i] != that.array[that.start + i]) { 733 return false; 734 } 735 } 736 return true; 737 } 738 return super.equals(object); 739 } 740 741 @Override 742 public int hashCode() { 743 int result = 1; 744 for (int i = start; i < end; i++) { 745 result = 31 * result + Ints.hashCode(array[i]); 746 } 747 return result; 748 } 749 750 @Override 751 public String toString() { 752 StringBuilder builder = new StringBuilder(size() * 5); 753 builder.append('[').append(array[start]); 754 for (int i = start + 1; i < end; i++) { 755 builder.append(", ").append(array[i]); 756 } 757 return builder.append(']').toString(); 758 } 759 760 int[] toIntArray() { 761 return Arrays.copyOfRange(array, start, end); 762 } 763 764 private static final long serialVersionUID = 0; 765 } 766 767 /** 768 * Parses the specified string as a signed decimal integer value. The ASCII character {@code '-'} 769 * (<code>'\u002D'</code>) is recognized as the minus sign. 770 * 771 * <p>Unlike {@link Integer#parseInt(String)}, this method returns {@code null} instead of 772 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 773 * and returns {@code null} if non-ASCII digits are present in the string. 774 * 775 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 776 * the change to {@link Integer#parseInt(String)} for that version. 777 * 778 * @param string the string representation of an integer value 779 * @return the integer value represented by {@code string}, or {@code null} if {@code string} has 780 * a length of zero or cannot be parsed as an integer value 781 * @throws NullPointerException if {@code string} is {@code null} 782 * @since 11.0 783 */ 784 @CheckForNull 785 public static Integer tryParse(String string) { 786 return tryParse(string, 10); 787 } 788 789 /** 790 * Parses the specified string as a signed integer value using the specified radix. The ASCII 791 * character {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 792 * 793 * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns {@code null} instead of 794 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 795 * and returns {@code null} if non-ASCII digits are present in the string. 796 * 797 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 798 * the change to {@link Integer#parseInt(String, int)} for that version. 799 * 800 * @param string the string representation of an integer value 801 * @param radix the radix to use when parsing 802 * @return the integer value represented by {@code string} using {@code radix}, or {@code null} if 803 * {@code string} has a length of zero or cannot be parsed as an integer value 804 * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix > 805 * Character.MAX_RADIX} 806 * @throws NullPointerException if {@code string} is {@code null} 807 * @since 19.0 808 */ 809 @CheckForNull 810 public static Integer tryParse(String string, int radix) { 811 Long result = Longs.tryParse(string, radix); 812 if (result == null || result.longValue() != result.intValue()) { 813 return null; 814 } else { 815 return result.intValue(); 816 } 817 } 818}