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.base.Converter; 024import com.google.errorprone.annotations.InlineMe; 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 long} primitives, that are not already found in 037 * either {@link Long} 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 046@ElementTypesAreNonnullByDefault 047public final class Longs { 048 private Longs() {} 049 050 /** 051 * The number of bytes required to represent a primitive {@code long} value. 052 * 053 * <p><b>Java 8+ users:</b> use {@link Long#BYTES} instead. 054 */ 055 public static final int BYTES = Long.SIZE / Byte.SIZE; 056 057 /** 058 * The largest power of two that can be represented as a {@code long}. 059 * 060 * @since 10.0 061 */ 062 public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2); 063 064 /** 065 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Long) 066 * value).hashCode()}. 067 * 068 * <p>This method always return the value specified by {@link Long#hashCode()} in java, which 069 * might be different from {@code ((Long) value).hashCode()} in GWT because {@link 070 * Long#hashCode()} in GWT does not obey the JRE contract. 071 * 072 * <p><b>Java 8+ users:</b> use {@link Long#hashCode(long)} instead. 073 * 074 * @param value a primitive {@code long} value 075 * @return a hash code for the value 076 */ 077 public static int hashCode(long value) { 078 return (int) (value ^ (value >>> 32)); 079 } 080 081 /** 082 * Compares the two specified {@code long} values. The sign of the value returned is the same as 083 * that of {@code ((Long) a).compareTo(b)}. 084 * 085 * <p><b>Note:</b> this method is now unnecessary and should be treated as deprecated; use the 086 * equivalent {@link Long#compare} method instead. 087 * 088 * @param a the first {@code long} to compare 089 * @param b the second {@code long} to compare 090 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 091 * greater than {@code b}; or zero if they are equal 092 */ 093 @InlineMe(replacement = "Long.compare(a, b)") 094 public static int compare(long a, long b) { 095 return Long.compare(a, b); 096 } 097 098 /** 099 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. 100 * 101 * @param array an array of {@code long} values, possibly empty 102 * @param target a primitive {@code long} value 103 * @return {@code true} if {@code array[i] == target} for some value of {@code i} 104 */ 105 public static boolean contains(long[] array, long target) { 106 for (long value : array) { 107 if (value == target) { 108 return true; 109 } 110 } 111 return false; 112 } 113 114 /** 115 * Returns the index of the first appearance of the value {@code target} in {@code array}. 116 * 117 * @param array an array of {@code long} values, possibly empty 118 * @param target a primitive {@code long} value 119 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 120 * such index exists. 121 */ 122 public static int indexOf(long[] array, long target) { 123 return indexOf(array, target, 0, array.length); 124 } 125 126 // TODO(kevinb): consider making this public 127 private static int indexOf(long[] array, long target, int start, int end) { 128 for (int i = start; i < end; i++) { 129 if (array[i] == target) { 130 return i; 131 } 132 } 133 return -1; 134 } 135 136 /** 137 * Returns the start position of the first occurrence of the specified {@code target} within 138 * {@code array}, or {@code -1} if there is no such occurrence. 139 * 140 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 141 * i, i + target.length)} contains exactly the same elements as {@code target}. 142 * 143 * @param array the array to search for the sequence {@code target} 144 * @param target the array to search for as a sub-sequence of {@code array} 145 */ 146 public static int indexOf(long[] array, long[] target) { 147 checkNotNull(array, "array"); 148 checkNotNull(target, "target"); 149 if (target.length == 0) { 150 return 0; 151 } 152 153 outer: 154 for (int i = 0; i < array.length - target.length + 1; i++) { 155 for (int j = 0; j < target.length; j++) { 156 if (array[i + j] != target[j]) { 157 continue outer; 158 } 159 } 160 return i; 161 } 162 return -1; 163 } 164 165 /** 166 * Returns the index of the last appearance of the value {@code target} in {@code array}. 167 * 168 * @param array an array of {@code long} values, possibly empty 169 * @param target a primitive {@code long} value 170 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 171 * such index exists. 172 */ 173 public static int lastIndexOf(long[] array, long target) { 174 return lastIndexOf(array, target, 0, array.length); 175 } 176 177 // TODO(kevinb): consider making this public 178 private static int lastIndexOf(long[] array, long target, int start, int end) { 179 for (int i = end - 1; i >= start; i--) { 180 if (array[i] == target) { 181 return i; 182 } 183 } 184 return -1; 185 } 186 187 /** 188 * Returns the least value present in {@code array}. 189 * 190 * @param array a <i>nonempty</i> array of {@code long} values 191 * @return the value present in {@code array} that is less than or equal to every other value in 192 * the array 193 * @throws IllegalArgumentException if {@code array} is empty 194 */ 195 public static long min(long... array) { 196 checkArgument(array.length > 0); 197 long min = array[0]; 198 for (int i = 1; i < array.length; i++) { 199 if (array[i] < min) { 200 min = array[i]; 201 } 202 } 203 return min; 204 } 205 206 /** 207 * Returns the greatest value present in {@code array}. 208 * 209 * @param array a <i>nonempty</i> array of {@code long} values 210 * @return the value present in {@code array} that is greater than or equal to every other value 211 * in the array 212 * @throws IllegalArgumentException if {@code array} is empty 213 */ 214 public static long max(long... array) { 215 checkArgument(array.length > 0); 216 long max = array[0]; 217 for (int i = 1; i < array.length; i++) { 218 if (array[i] > max) { 219 max = array[i]; 220 } 221 } 222 return max; 223 } 224 225 /** 226 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 227 * 228 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 229 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 230 * value} is greater than {@code max}, {@code max} is returned. 231 * 232 * @param value the {@code long} value to constrain 233 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 234 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 235 * @throws IllegalArgumentException if {@code min > max} 236 * @since 21.0 237 */ 238 public static long constrainToRange(long value, long min, long max) { 239 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 240 return Math.min(Math.max(value, min), max); 241 } 242 243 /** 244 * Returns the values from each provided array combined into a single array. For example, {@code 245 * concat(new long[] {a, b}, new long[] {}, new long[] {c}} returns the array {@code {a, b, c}}. 246 * 247 * @param arrays zero or more {@code long} arrays 248 * @return a single array containing all the values from the source arrays, in order 249 * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit 250 * in an {@code int} 251 */ 252 public static long[] concat(long[]... arrays) { 253 long length = 0; 254 for (long[] array : arrays) { 255 length += array.length; 256 } 257 long[] result = new long[checkNoOverflow(length)]; 258 int pos = 0; 259 for (long[] array : arrays) { 260 System.arraycopy(array, 0, result, pos, array.length); 261 pos += array.length; 262 } 263 return result; 264 } 265 266 private static int checkNoOverflow(long result) { 267 checkArgument( 268 result == (int) result, 269 "the total number of elements (%s) in the arrays must fit in an int", 270 result); 271 return (int) result; 272 } 273 274 /** 275 * Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to 276 * {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value {@code 277 * 0x1213141516171819L} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 278 * 0x18, 0x19}}. 279 * 280 * <p>If you need to convert and concatenate several values (possibly even of different types), 281 * use a shared {@link java.nio.ByteBuffer} instance, or use {@link 282 * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer. 283 */ 284 public static byte[] toByteArray(long value) { 285 // Note that this code needs to stay compatible with GWT, which has known 286 // bugs when narrowing byte casts of long values occur. 287 byte[] result = new byte[8]; 288 for (int i = 7; i >= 0; i--) { 289 result[i] = (byte) (value & 0xffL); 290 value >>= 8; 291 } 292 return result; 293 } 294 295 /** 296 * Returns the {@code long} value whose big-endian representation is stored in the first 8 bytes 297 * of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getLong()}. For example, the 298 * input byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the 299 * {@code long} value {@code 0x1213141516171819L}. 300 * 301 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more 302 * flexibility at little cost in readability. 303 * 304 * @throws IllegalArgumentException if {@code bytes} has fewer than 8 elements 305 */ 306 public static long fromByteArray(byte[] bytes) { 307 checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES); 308 return fromBytes( 309 bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]); 310 } 311 312 /** 313 * Returns the {@code long} value whose byte representation is the given 8 bytes, in big-endian 314 * order; equivalent to {@code Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}. 315 * 316 * @since 7.0 317 */ 318 public static long fromBytes( 319 byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8) { 320 return (b1 & 0xFFL) << 56 321 | (b2 & 0xFFL) << 48 322 | (b3 & 0xFFL) << 40 323 | (b4 & 0xFFL) << 32 324 | (b5 & 0xFFL) << 24 325 | (b6 & 0xFFL) << 16 326 | (b7 & 0xFFL) << 8 327 | (b8 & 0xFFL); 328 } 329 330 /* 331 * Moving asciiDigits into this static holder class lets ProGuard eliminate and inline the Longs 332 * class. 333 */ 334 static final class AsciiDigits { 335 private AsciiDigits() {} 336 337 private static final byte[] asciiDigits; 338 339 static { 340 byte[] result = new byte[128]; 341 Arrays.fill(result, (byte) -1); 342 for (int i = 0; i < 10; i++) { 343 result['0' + i] = (byte) i; 344 } 345 for (int i = 0; i < 26; i++) { 346 result['A' + i] = (byte) (10 + i); 347 result['a' + i] = (byte) (10 + i); 348 } 349 asciiDigits = result; 350 } 351 352 static int digit(char c) { 353 return (c < 128) ? asciiDigits[c] : -1; 354 } 355 } 356 357 /** 358 * Parses the specified string as a signed decimal long value. The ASCII character {@code '-'} ( 359 * <code>'\u002D'</code>) is recognized as the minus sign. 360 * 361 * <p>Unlike {@link Long#parseLong(String)}, this method returns {@code null} instead of throwing 362 * an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns 363 * {@code null} if non-ASCII digits are present in the string. 364 * 365 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even though {@link 366 * Integer#parseInt(String)} accepts them. 367 * 368 * @param string the string representation of a long value 369 * @return the long value represented by {@code string}, or {@code null} if {@code string} has a 370 * length of zero or cannot be parsed as a long value 371 * @throws NullPointerException if {@code string} is {@code null} 372 * @since 14.0 373 */ 374 @CheckForNull 375 public static Long tryParse(String string) { 376 return tryParse(string, 10); 377 } 378 379 /** 380 * Parses the specified string as a signed long value using the specified radix. The ASCII 381 * character {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 382 * 383 * <p>Unlike {@link Long#parseLong(String, int)}, this method returns {@code null} instead of 384 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 385 * and returns {@code null} if non-ASCII digits are present in the string. 386 * 387 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even though {@link 388 * Integer#parseInt(String)} accepts them. 389 * 390 * @param string the string representation of a long value 391 * @param radix the radix to use when parsing 392 * @return the long value represented by {@code string} using {@code radix}, or {@code null} if 393 * {@code string} has a length of zero or cannot be parsed as a long value 394 * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix > 395 * Character.MAX_RADIX} 396 * @throws NullPointerException if {@code string} is {@code null} 397 * @since 19.0 398 */ 399 @CheckForNull 400 public static Long tryParse(String string, int radix) { 401 if (checkNotNull(string).isEmpty()) { 402 return null; 403 } 404 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) { 405 throw new IllegalArgumentException( 406 "radix must be between MIN_RADIX and MAX_RADIX but was " + radix); 407 } 408 boolean negative = string.charAt(0) == '-'; 409 int index = negative ? 1 : 0; 410 if (index == string.length()) { 411 return null; 412 } 413 int digit = AsciiDigits.digit(string.charAt(index++)); 414 if (digit < 0 || digit >= radix) { 415 return null; 416 } 417 long accum = -digit; 418 419 long cap = Long.MIN_VALUE / radix; 420 421 while (index < string.length()) { 422 digit = AsciiDigits.digit(string.charAt(index++)); 423 if (digit < 0 || digit >= radix || accum < cap) { 424 return null; 425 } 426 accum *= radix; 427 if (accum < Long.MIN_VALUE + digit) { 428 return null; 429 } 430 accum -= digit; 431 } 432 433 if (negative) { 434 return accum; 435 } else if (accum == Long.MIN_VALUE) { 436 return null; 437 } else { 438 return -accum; 439 } 440 } 441 442 private static final class LongConverter extends Converter<String, Long> implements Serializable { 443 static final Converter<String, Long> INSTANCE = new LongConverter(); 444 445 @Override 446 protected Long doForward(String value) { 447 return Long.decode(value); 448 } 449 450 @Override 451 protected String doBackward(Long value) { 452 return value.toString(); 453 } 454 455 @Override 456 public String toString() { 457 return "Longs.stringConverter()"; 458 } 459 460 private Object readResolve() { 461 return INSTANCE; 462 } 463 464 private static final long serialVersionUID = 1; 465 } 466 467 /** 468 * Returns a serializable converter object that converts between strings and longs using {@link 469 * Long#decode} and {@link Long#toString()}. The returned converter throws {@link 470 * NumberFormatException} if the input string is invalid. 471 * 472 * <p><b>Warning:</b> please see {@link Long#decode} to understand exactly how strings are parsed. 473 * For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the value 474 * {@code 83L}. 475 * 476 * @since 16.0 477 */ 478 public static Converter<String, Long> stringConverter() { 479 return LongConverter.INSTANCE; 480 } 481 482 /** 483 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 484 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 485 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 486 * returned, containing the values of {@code array}, and zeroes in the remaining places. 487 * 488 * @param array the source array 489 * @param minLength the minimum length the returned array must guarantee 490 * @param padding an extra amount to "grow" the array by if growth is necessary 491 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 492 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 493 * minLength} 494 */ 495 public static long[] ensureCapacity(long[] array, int minLength, int padding) { 496 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 497 checkArgument(padding >= 0, "Invalid padding: %s", padding); 498 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 499 } 500 501 /** 502 * Returns a string containing the supplied {@code long} values separated by {@code separator}. 503 * For example, {@code join("-", 1L, 2L, 3L)} returns the string {@code "1-2-3"}. 504 * 505 * @param separator the text that should appear between consecutive values in the resulting string 506 * (but not at the start or end) 507 * @param array an array of {@code long} values, possibly empty 508 */ 509 public static String join(String separator, long... array) { 510 checkNotNull(separator); 511 if (array.length == 0) { 512 return ""; 513 } 514 515 // For pre-sizing a builder, just get the right order of magnitude 516 StringBuilder builder = new StringBuilder(array.length * 10); 517 builder.append(array[0]); 518 for (int i = 1; i < array.length; i++) { 519 builder.append(separator).append(array[i]); 520 } 521 return builder.toString(); 522 } 523 524 /** 525 * Returns a comparator that compares two {@code long} arrays <a 526 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 527 * compares, using {@link #compare(long, long)}), the first pair of values that follow any common 528 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 529 * example, {@code [] < [1L] < [1L, 2L] < [2L]}. 530 * 531 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 532 * support only identity equality), but it is consistent with {@link Arrays#equals(long[], 533 * long[])}. 534 * 535 * @since 2.0 536 */ 537 public static Comparator<long[]> lexicographicalComparator() { 538 return LexicographicalComparator.INSTANCE; 539 } 540 541 private enum LexicographicalComparator implements Comparator<long[]> { 542 INSTANCE; 543 544 @Override 545 public int compare(long[] left, long[] right) { 546 int minLength = Math.min(left.length, right.length); 547 for (int i = 0; i < minLength; i++) { 548 int result = Long.compare(left[i], right[i]); 549 if (result != 0) { 550 return result; 551 } 552 } 553 return left.length - right.length; 554 } 555 556 @Override 557 public String toString() { 558 return "Longs.lexicographicalComparator()"; 559 } 560 } 561 562 /** 563 * Sorts the elements of {@code array} in descending order. 564 * 565 * @since 23.1 566 */ 567 public static void sortDescending(long[] array) { 568 checkNotNull(array); 569 sortDescending(array, 0, array.length); 570 } 571 572 /** 573 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 574 * exclusive in descending order. 575 * 576 * @since 23.1 577 */ 578 public static void sortDescending(long[] array, int fromIndex, int toIndex) { 579 checkNotNull(array); 580 checkPositionIndexes(fromIndex, toIndex, array.length); 581 Arrays.sort(array, fromIndex, toIndex); 582 reverse(array, fromIndex, toIndex); 583 } 584 585 /** 586 * Reverses the elements of {@code array}. This is equivalent to {@code 587 * Collections.reverse(Longs.asList(array))}, but is likely to be more efficient. 588 * 589 * @since 23.1 590 */ 591 public static void reverse(long[] array) { 592 checkNotNull(array); 593 reverse(array, 0, array.length); 594 } 595 596 /** 597 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 598 * exclusive. This is equivalent to {@code 599 * Collections.reverse(Longs.asList(array).subList(fromIndex, toIndex))}, but is likely to be more 600 * efficient. 601 * 602 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 603 * {@code toIndex > fromIndex} 604 * @since 23.1 605 */ 606 public static void reverse(long[] array, int fromIndex, int toIndex) { 607 checkNotNull(array); 608 checkPositionIndexes(fromIndex, toIndex, array.length); 609 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 610 long tmp = array[i]; 611 array[i] = array[j]; 612 array[j] = tmp; 613 } 614 } 615 616 /** 617 * Performs a right rotation of {@code array} of "distance" places, so that the first element is 618 * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance 619 * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Longs.asList(array), 620 * distance)}, but is considerably faster and avoids allocation and garbage collection. 621 * 622 * <p>The provided "distance" may be negative, which will rotate left. 623 * 624 * @since 32.0.0 625 */ 626 public static void rotate(long[] array, int distance) { 627 rotate(array, distance, 0, array.length); 628 } 629 630 /** 631 * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code 632 * toIndex} exclusive. This is equivalent to {@code 633 * Collections.rotate(Longs.asList(array).subList(fromIndex, toIndex), distance)}, but is 634 * considerably faster and avoids allocations and garbage collection. 635 * 636 * <p>The provided "distance" may be negative, which will rotate left. 637 * 638 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 639 * {@code toIndex > fromIndex} 640 * @since 32.0.0 641 */ 642 public static void rotate(long[] array, int distance, int fromIndex, int toIndex) { 643 // See Ints.rotate for more details about possible algorithms here. 644 checkNotNull(array); 645 checkPositionIndexes(fromIndex, toIndex, array.length); 646 if (array.length <= 1) { 647 return; 648 } 649 650 int length = toIndex - fromIndex; 651 // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many 652 // places left to rotate. 653 int m = -distance % length; 654 m = (m < 0) ? m + length : m; 655 // The current index of what will become the first element of the rotated section. 656 int newFirstIndex = m + fromIndex; 657 if (newFirstIndex == fromIndex) { 658 return; 659 } 660 661 reverse(array, fromIndex, newFirstIndex); 662 reverse(array, newFirstIndex, toIndex); 663 reverse(array, fromIndex, toIndex); 664 } 665 666 /** 667 * Returns an array containing each value of {@code collection}, converted to a {@code long} value 668 * in the manner of {@link Number#longValue}. 669 * 670 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 671 * Calling this method is as thread-safe as calling that method. 672 * 673 * @param collection a collection of {@code Number} instances 674 * @return an array containing the same values as {@code collection}, in the same order, converted 675 * to primitives 676 * @throws NullPointerException if {@code collection} or any of its elements is null 677 * @since 1.0 (parameter was {@code Collection<Long>} before 12.0) 678 */ 679 public static long[] toArray(Collection<? extends Number> collection) { 680 if (collection instanceof LongArrayAsList) { 681 return ((LongArrayAsList) collection).toLongArray(); 682 } 683 684 Object[] boxedArray = collection.toArray(); 685 int len = boxedArray.length; 686 long[] array = new long[len]; 687 for (int i = 0; i < len; i++) { 688 // checkNotNull for GWT (do not optimize) 689 array[i] = ((Number) checkNotNull(boxedArray[i])).longValue(); 690 } 691 return array; 692 } 693 694 /** 695 * Returns a fixed-size list backed by the specified array, similar to {@link 696 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 697 * set a value to {@code null} will result in a {@link NullPointerException}. 698 * 699 * <p>The returned list maintains the values, but not the identities, of {@code Long} objects 700 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 701 * the returned list is unspecified. 702 * 703 * <p>The returned list is serializable. 704 * 705 * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableLongArray} 706 * instead, which has an {@link ImmutableLongArray#asList asList} view. 707 * 708 * @param backingArray the array to back the list 709 * @return a list view of the array 710 */ 711 public static List<Long> asList(long... backingArray) { 712 if (backingArray.length == 0) { 713 return Collections.emptyList(); 714 } 715 return new LongArrayAsList(backingArray); 716 } 717 718 @GwtCompatible 719 private static class LongArrayAsList extends AbstractList<Long> 720 implements RandomAccess, Serializable { 721 final long[] array; 722 final int start; 723 final int end; 724 725 LongArrayAsList(long[] array) { 726 this(array, 0, array.length); 727 } 728 729 LongArrayAsList(long[] array, int start, int end) { 730 this.array = array; 731 this.start = start; 732 this.end = end; 733 } 734 735 @Override 736 public int size() { 737 return end - start; 738 } 739 740 @Override 741 public boolean isEmpty() { 742 return false; 743 } 744 745 @Override 746 public Long get(int index) { 747 checkElementIndex(index, size()); 748 return array[start + index]; 749 } 750 751 @Override 752 public boolean contains(@CheckForNull Object target) { 753 // Overridden to prevent a ton of boxing 754 return (target instanceof Long) && Longs.indexOf(array, (Long) target, start, end) != -1; 755 } 756 757 @Override 758 public int indexOf(@CheckForNull Object target) { 759 // Overridden to prevent a ton of boxing 760 if (target instanceof Long) { 761 int i = Longs.indexOf(array, (Long) target, start, end); 762 if (i >= 0) { 763 return i - start; 764 } 765 } 766 return -1; 767 } 768 769 @Override 770 public int lastIndexOf(@CheckForNull Object target) { 771 // Overridden to prevent a ton of boxing 772 if (target instanceof Long) { 773 int i = Longs.lastIndexOf(array, (Long) target, start, end); 774 if (i >= 0) { 775 return i - start; 776 } 777 } 778 return -1; 779 } 780 781 @Override 782 public Long set(int index, Long element) { 783 checkElementIndex(index, size()); 784 long oldValue = array[start + index]; 785 // checkNotNull for GWT (do not optimize) 786 array[start + index] = checkNotNull(element); 787 return oldValue; 788 } 789 790 @Override 791 public List<Long> subList(int fromIndex, int toIndex) { 792 int size = size(); 793 checkPositionIndexes(fromIndex, toIndex, size); 794 if (fromIndex == toIndex) { 795 return Collections.emptyList(); 796 } 797 return new LongArrayAsList(array, start + fromIndex, start + toIndex); 798 } 799 800 @Override 801 public boolean equals(@CheckForNull Object object) { 802 if (object == this) { 803 return true; 804 } 805 if (object instanceof LongArrayAsList) { 806 LongArrayAsList that = (LongArrayAsList) object; 807 int size = size(); 808 if (that.size() != size) { 809 return false; 810 } 811 for (int i = 0; i < size; i++) { 812 if (array[start + i] != that.array[that.start + i]) { 813 return false; 814 } 815 } 816 return true; 817 } 818 return super.equals(object); 819 } 820 821 @Override 822 public int hashCode() { 823 int result = 1; 824 for (int i = start; i < end; i++) { 825 result = 31 * result + Longs.hashCode(array[i]); 826 } 827 return result; 828 } 829 830 @Override 831 public String toString() { 832 StringBuilder builder = new StringBuilder(size() * 10); 833 builder.append('[').append(array[start]); 834 for (int i = start + 1; i < end; i++) { 835 builder.append(", ").append(array[i]); 836 } 837 return builder.append(']').toString(); 838 } 839 840 long[] toLongArray() { 841 return Arrays.copyOfRange(array, start, end); 842 } 843 844 private static final long serialVersionUID = 0; 845 } 846}