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 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 long} primitives, that are not already found in 036 * either {@link Long} 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 Longs { 047 private Longs() {} 048 049 /** 050 * The number of bytes required to represent a primitive {@code long} value. 051 * 052 * <p><b>Java 8 users:</b> use {@link Long#BYTES} instead. 053 */ 054 public static final int BYTES = Long.SIZE / Byte.SIZE; 055 056 /** 057 * The largest power of two that can be represented as a {@code long}. 058 * 059 * @since 10.0 060 */ 061 public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2); 062 063 /** 064 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Long) 065 * value).hashCode()}. 066 * 067 * <p>This method always return the value specified by {@link Long#hashCode()} in java, which 068 * might be different from {@code ((Long) value).hashCode()} in GWT because {@link 069 * Long#hashCode()} in GWT does not obey the JRE contract. 070 * 071 * <p><b>Java 8 users:</b> use {@link Long#hashCode(long)} instead. 072 * 073 * @param value a primitive {@code long} value 074 * @return a hash code for the value 075 */ 076 public static int hashCode(long value) { 077 return (int) (value ^ (value >>> 32)); 078 } 079 080 /** 081 * Compares the two specified {@code long} values. The sign of the value returned is the same as 082 * that of {@code ((Long) a).compareTo(b)}. 083 * 084 * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the 085 * equivalent {@link Long#compare} method instead. 086 * 087 * @param a the first {@code long} to compare 088 * @param b the second {@code long} to compare 089 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is 090 * greater than {@code b}; or zero if they are equal 091 */ 092 public static int compare(long a, long b) { 093 return (a < b) ? -1 : ((a > b) ? 1 : 0); 094 } 095 096 /** 097 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. 098 * 099 * @param array an array of {@code long} values, possibly empty 100 * @param target a primitive {@code long} value 101 * @return {@code true} if {@code array[i] == target} for some value of {@code i} 102 */ 103 public static boolean contains(long[] array, long target) { 104 for (long value : array) { 105 if (value == target) { 106 return true; 107 } 108 } 109 return false; 110 } 111 112 /** 113 * Returns the index of the first appearance of the value {@code target} in {@code array}. 114 * 115 * @param array an array of {@code long} values, possibly empty 116 * @param target a primitive {@code long} value 117 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no 118 * such index exists. 119 */ 120 public static int indexOf(long[] array, long target) { 121 return indexOf(array, target, 0, array.length); 122 } 123 124 // TODO(kevinb): consider making this public 125 private static int indexOf(long[] array, long target, int start, int end) { 126 for (int i = start; i < end; i++) { 127 if (array[i] == target) { 128 return i; 129 } 130 } 131 return -1; 132 } 133 134 /** 135 * Returns the start position of the first occurrence of the specified {@code target} within 136 * {@code array}, or {@code -1} if there is no such occurrence. 137 * 138 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array, 139 * i, i + target.length)} contains exactly the same elements as {@code target}. 140 * 141 * @param array the array to search for the sequence {@code target} 142 * @param target the array to search for as a sub-sequence of {@code array} 143 */ 144 public static int indexOf(long[] array, long[] target) { 145 checkNotNull(array, "array"); 146 checkNotNull(target, "target"); 147 if (target.length == 0) { 148 return 0; 149 } 150 151 outer: 152 for (int i = 0; i < array.length - target.length + 1; i++) { 153 for (int j = 0; j < target.length; j++) { 154 if (array[i + j] != target[j]) { 155 continue outer; 156 } 157 } 158 return i; 159 } 160 return -1; 161 } 162 163 /** 164 * Returns the index of the last appearance of the value {@code target} in {@code array}. 165 * 166 * @param array an array of {@code long} values, possibly empty 167 * @param target a primitive {@code long} value 168 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no 169 * such index exists. 170 */ 171 public static int lastIndexOf(long[] array, long target) { 172 return lastIndexOf(array, target, 0, array.length); 173 } 174 175 // TODO(kevinb): consider making this public 176 private static int lastIndexOf(long[] array, long target, int start, int end) { 177 for (int i = end - 1; i >= start; i--) { 178 if (array[i] == target) { 179 return i; 180 } 181 } 182 return -1; 183 } 184 185 /** 186 * Returns the least value present in {@code array}. 187 * 188 * @param array a <i>nonempty</i> array of {@code long} values 189 * @return the value present in {@code array} that is less than or equal to every other value in 190 * the array 191 * @throws IllegalArgumentException if {@code array} is empty 192 */ 193 public static long min(long... array) { 194 checkArgument(array.length > 0); 195 long min = array[0]; 196 for (int i = 1; i < array.length; i++) { 197 if (array[i] < min) { 198 min = array[i]; 199 } 200 } 201 return min; 202 } 203 204 /** 205 * Returns the greatest value present in {@code array}. 206 * 207 * @param array a <i>nonempty</i> array of {@code long} values 208 * @return the value present in {@code array} that is greater than or equal to every other value 209 * in the array 210 * @throws IllegalArgumentException if {@code array} is empty 211 */ 212 public static long max(long... array) { 213 checkArgument(array.length > 0); 214 long max = array[0]; 215 for (int i = 1; i < array.length; i++) { 216 if (array[i] > max) { 217 max = array[i]; 218 } 219 } 220 return max; 221 } 222 223 /** 224 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}. 225 * 226 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned 227 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code 228 * value} is greater than {@code max}, {@code max} is returned. 229 * 230 * @param value the {@code long} value to constrain 231 * @param min the lower bound (inclusive) of the range to constrain {@code value} to 232 * @param max the upper bound (inclusive) of the range to constrain {@code value} to 233 * @throws IllegalArgumentException if {@code min > max} 234 * @since 21.0 235 */ 236 public static long constrainToRange(long value, long min, long max) { 237 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max); 238 return Math.min(Math.max(value, min), max); 239 } 240 241 /** 242 * Returns the values from each provided array combined into a single array. For example, {@code 243 * concat(new long[] {a, b}, new long[] {}, new long[] {c}} returns the array {@code {a, b, c}}. 244 * 245 * @param arrays zero or more {@code long} arrays 246 * @return a single array containing all the values from the source arrays, in order 247 * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit 248 * in an {@code int} 249 */ 250 public static long[] concat(long[]... arrays) { 251 long length = 0; 252 for (long[] array : arrays) { 253 length += array.length; 254 } 255 long[] result = new long[checkNoOverflow(length)]; 256 int pos = 0; 257 for (long[] array : arrays) { 258 System.arraycopy(array, 0, result, pos, array.length); 259 pos += array.length; 260 } 261 return result; 262 } 263 264 private static int checkNoOverflow(long result) { 265 checkArgument( 266 result == (int) result, 267 "the total number of elements (%s) in the arrays must fit in an int", 268 result); 269 return (int) result; 270 } 271 272 /** 273 * Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to 274 * {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value {@code 275 * 0x1213141516171819L} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 276 * 0x18, 0x19}}. 277 * 278 * <p>If you need to convert and concatenate several values (possibly even of different types), 279 * use a shared {@link java.nio.ByteBuffer} instance, or use {@link 280 * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer. 281 */ 282 public static byte[] toByteArray(long value) { 283 // Note that this code needs to stay compatible with GWT, which has known 284 // bugs when narrowing byte casts of long values occur. 285 byte[] result = new byte[8]; 286 for (int i = 7; i >= 0; i--) { 287 result[i] = (byte) (value & 0xffL); 288 value >>= 8; 289 } 290 return result; 291 } 292 293 /** 294 * Returns the {@code long} value whose big-endian representation is stored in the first 8 bytes 295 * of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getLong()}. For example, the 296 * input byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the 297 * {@code long} value {@code 0x1213141516171819L}. 298 * 299 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more 300 * flexibility at little cost in readability. 301 * 302 * @throws IllegalArgumentException if {@code bytes} has fewer than 8 elements 303 */ 304 public static long fromByteArray(byte[] bytes) { 305 checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES); 306 return fromBytes( 307 bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]); 308 } 309 310 /** 311 * Returns the {@code long} value whose byte representation is the given 8 bytes, in big-endian 312 * order; equivalent to {@code Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}. 313 * 314 * @since 7.0 315 */ 316 public static long fromBytes( 317 byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8) { 318 return (b1 & 0xFFL) << 56 319 | (b2 & 0xFFL) << 48 320 | (b3 & 0xFFL) << 40 321 | (b4 & 0xFFL) << 32 322 | (b5 & 0xFFL) << 24 323 | (b6 & 0xFFL) << 16 324 | (b7 & 0xFFL) << 8 325 | (b8 & 0xFFL); 326 } 327 328 /* 329 * Moving asciiDigits into this static holder class lets ProGuard eliminate and inline the Longs 330 * class. 331 */ 332 static final class AsciiDigits { 333 private AsciiDigits() {} 334 335 private static final byte[] asciiDigits; 336 337 static { 338 byte[] result = new byte[128]; 339 Arrays.fill(result, (byte) -1); 340 for (int i = 0; i < 10; i++) { 341 result['0' + i] = (byte) i; 342 } 343 for (int i = 0; i < 26; i++) { 344 result['A' + i] = (byte) (10 + i); 345 result['a' + i] = (byte) (10 + i); 346 } 347 asciiDigits = result; 348 } 349 350 static int digit(char c) { 351 return (c < 128) ? asciiDigits[c] : -1; 352 } 353 } 354 355 /** 356 * Parses the specified string as a signed decimal long value. The ASCII character {@code '-'} ( 357 * <code>'\u002D'</code>) is recognized as the minus sign. 358 * 359 * <p>Unlike {@link Long#parseLong(String)}, this method returns {@code null} instead of throwing 360 * an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns 361 * {@code null} if non-ASCII digits are present in the string. 362 * 363 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 364 * the change to {@link Long#parseLong(String)} for that version. 365 * 366 * @param string the string representation of a long value 367 * @return the long value represented by {@code string}, or {@code null} if {@code string} has a 368 * length of zero or cannot be parsed as a long value 369 * @throws NullPointerException if {@code string} is {@code null} 370 * @since 14.0 371 */ 372 @CheckForNull 373 public static Long tryParse(String string) { 374 return tryParse(string, 10); 375 } 376 377 /** 378 * Parses the specified string as a signed long value using the specified radix. The ASCII 379 * character {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign. 380 * 381 * <p>Unlike {@link Long#parseLong(String, int)}, this method returns {@code null} instead of 382 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits, 383 * and returns {@code null} if non-ASCII digits are present in the string. 384 * 385 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite 386 * the change to {@link Long#parseLong(String, int)} for that version. 387 * 388 * @param string the string representation of a long value 389 * @param radix the radix to use when parsing 390 * @return the long value represented by {@code string} using {@code radix}, or {@code null} if 391 * {@code string} has a length of zero or cannot be parsed as a long value 392 * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix > 393 * Character.MAX_RADIX} 394 * @throws NullPointerException if {@code string} is {@code null} 395 * @since 19.0 396 */ 397 @CheckForNull 398 public static Long tryParse(String string, int radix) { 399 if (checkNotNull(string).isEmpty()) { 400 return null; 401 } 402 if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) { 403 throw new IllegalArgumentException( 404 "radix must be between MIN_RADIX and MAX_RADIX but was " + radix); 405 } 406 boolean negative = string.charAt(0) == '-'; 407 int index = negative ? 1 : 0; 408 if (index == string.length()) { 409 return null; 410 } 411 int digit = AsciiDigits.digit(string.charAt(index++)); 412 if (digit < 0 || digit >= radix) { 413 return null; 414 } 415 long accum = -digit; 416 417 long cap = Long.MIN_VALUE / radix; 418 419 while (index < string.length()) { 420 digit = AsciiDigits.digit(string.charAt(index++)); 421 if (digit < 0 || digit >= radix || accum < cap) { 422 return null; 423 } 424 accum *= radix; 425 if (accum < Long.MIN_VALUE + digit) { 426 return null; 427 } 428 accum -= digit; 429 } 430 431 if (negative) { 432 return accum; 433 } else if (accum == Long.MIN_VALUE) { 434 return null; 435 } else { 436 return -accum; 437 } 438 } 439 440 private static final class LongConverter extends Converter<String, Long> implements Serializable { 441 static final LongConverter INSTANCE = new LongConverter(); 442 443 @Override 444 protected Long doForward(String value) { 445 return Long.decode(value); 446 } 447 448 @Override 449 protected String doBackward(Long value) { 450 return value.toString(); 451 } 452 453 @Override 454 public String toString() { 455 return "Longs.stringConverter()"; 456 } 457 458 private Object readResolve() { 459 return INSTANCE; 460 } 461 462 private static final long serialVersionUID = 1; 463 } 464 465 /** 466 * Returns a serializable converter object that converts between strings and longs using {@link 467 * Long#decode} and {@link Long#toString()}. The returned converter throws {@link 468 * NumberFormatException} if the input string is invalid. 469 * 470 * <p><b>Warning:</b> please see {@link Long#decode} to understand exactly how strings are parsed. 471 * For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the value 472 * {@code 83L}. 473 * 474 * @since 16.0 475 */ 476 public static Converter<String, Long> stringConverter() { 477 return LongConverter.INSTANCE; 478 } 479 480 /** 481 * Returns an array containing the same values as {@code array}, but guaranteed to be of a 482 * specified minimum length. If {@code array} already has a length of at least {@code minLength}, 483 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is 484 * returned, containing the values of {@code array}, and zeroes in the remaining places. 485 * 486 * @param array the source array 487 * @param minLength the minimum length the returned array must guarantee 488 * @param padding an extra amount to "grow" the array by if growth is necessary 489 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative 490 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code 491 * minLength} 492 */ 493 public static long[] ensureCapacity(long[] array, int minLength, int padding) { 494 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength); 495 checkArgument(padding >= 0, "Invalid padding: %s", padding); 496 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array; 497 } 498 499 /** 500 * Returns a string containing the supplied {@code long} values separated by {@code separator}. 501 * For example, {@code join("-", 1L, 2L, 3L)} returns the string {@code "1-2-3"}. 502 * 503 * @param separator the text that should appear between consecutive values in the resulting string 504 * (but not at the start or end) 505 * @param array an array of {@code long} values, possibly empty 506 */ 507 public static String join(String separator, long... array) { 508 checkNotNull(separator); 509 if (array.length == 0) { 510 return ""; 511 } 512 513 // For pre-sizing a builder, just get the right order of magnitude 514 StringBuilder builder = new StringBuilder(array.length * 10); 515 builder.append(array[0]); 516 for (int i = 1; i < array.length; i++) { 517 builder.append(separator).append(array[i]); 518 } 519 return builder.toString(); 520 } 521 522 /** 523 * Returns a comparator that compares two {@code long} arrays <a 524 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it 525 * compares, using {@link #compare(long, long)}), the first pair of values that follow any common 526 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For 527 * example, {@code [] < [1L] < [1L, 2L] < [2L]}. 528 * 529 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays 530 * support only identity equality), but it is consistent with {@link Arrays#equals(long[], 531 * long[])}. 532 * 533 * @since 2.0 534 */ 535 public static Comparator<long[]> lexicographicalComparator() { 536 return LexicographicalComparator.INSTANCE; 537 } 538 539 private enum LexicographicalComparator implements Comparator<long[]> { 540 INSTANCE; 541 542 @Override 543 public int compare(long[] left, long[] right) { 544 int minLength = Math.min(left.length, right.length); 545 for (int i = 0; i < minLength; i++) { 546 int result = Longs.compare(left[i], right[i]); 547 if (result != 0) { 548 return result; 549 } 550 } 551 return left.length - right.length; 552 } 553 554 @Override 555 public String toString() { 556 return "Longs.lexicographicalComparator()"; 557 } 558 } 559 560 /** 561 * Sorts the elements of {@code array} in descending order. 562 * 563 * @since 23.1 564 */ 565 public static void sortDescending(long[] array) { 566 checkNotNull(array); 567 sortDescending(array, 0, array.length); 568 } 569 570 /** 571 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 572 * exclusive in descending order. 573 * 574 * @since 23.1 575 */ 576 public static void sortDescending(long[] array, int fromIndex, int toIndex) { 577 checkNotNull(array); 578 checkPositionIndexes(fromIndex, toIndex, array.length); 579 Arrays.sort(array, fromIndex, toIndex); 580 reverse(array, fromIndex, toIndex); 581 } 582 583 /** 584 * Reverses the elements of {@code array}. This is equivalent to {@code 585 * Collections.reverse(Longs.asList(array))}, but is likely to be more efficient. 586 * 587 * @since 23.1 588 */ 589 public static void reverse(long[] array) { 590 checkNotNull(array); 591 reverse(array, 0, array.length); 592 } 593 594 /** 595 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex} 596 * exclusive. This is equivalent to {@code 597 * Collections.reverse(Longs.asList(array).subList(fromIndex, toIndex))}, but is likely to be more 598 * efficient. 599 * 600 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 601 * {@code toIndex > fromIndex} 602 * @since 23.1 603 */ 604 public static void reverse(long[] array, int fromIndex, int toIndex) { 605 checkNotNull(array); 606 checkPositionIndexes(fromIndex, toIndex, array.length); 607 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) { 608 long tmp = array[i]; 609 array[i] = array[j]; 610 array[j] = tmp; 611 } 612 } 613 614 /** 615 * Performs a right rotation of {@code array} of "distance" places, so that the first element is 616 * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance 617 * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Longs.asList(array), 618 * distance)}, but is considerably faster and avoids allocation and garbage collection. 619 * 620 * <p>The provided "distance" may be negative, which will rotate left. 621 * 622 * @since 32.0.0 623 */ 624 public static void rotate(long[] array, int distance) { 625 rotate(array, distance, 0, array.length); 626 } 627 628 /** 629 * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code 630 * toIndex} exclusive. This is equivalent to {@code 631 * Collections.rotate(Longs.asList(array).subList(fromIndex, toIndex), distance)}, but is 632 * considerably faster and avoids allocations and garbage collection. 633 * 634 * <p>The provided "distance" may be negative, which will rotate left. 635 * 636 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or 637 * {@code toIndex > fromIndex} 638 * @since 32.0.0 639 */ 640 public static void rotate(long[] array, int distance, int fromIndex, int toIndex) { 641 // See Ints.rotate for more details about possible algorithms here. 642 checkNotNull(array); 643 checkPositionIndexes(fromIndex, toIndex, array.length); 644 if (array.length <= 1) { 645 return; 646 } 647 648 int length = toIndex - fromIndex; 649 // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many 650 // places left to rotate. 651 int m = -distance % length; 652 m = (m < 0) ? m + length : m; 653 // The current index of what will become the first element of the rotated section. 654 int newFirstIndex = m + fromIndex; 655 if (newFirstIndex == fromIndex) { 656 return; 657 } 658 659 reverse(array, fromIndex, newFirstIndex); 660 reverse(array, newFirstIndex, toIndex); 661 reverse(array, fromIndex, toIndex); 662 } 663 664 /** 665 * Returns an array containing each value of {@code collection}, converted to a {@code long} value 666 * in the manner of {@link Number#longValue}. 667 * 668 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}. 669 * Calling this method is as thread-safe as calling that method. 670 * 671 * @param collection a collection of {@code Number} instances 672 * @return an array containing the same values as {@code collection}, in the same order, converted 673 * to primitives 674 * @throws NullPointerException if {@code collection} or any of its elements is null 675 * @since 1.0 (parameter was {@code Collection<Long>} before 12.0) 676 */ 677 public static long[] toArray(Collection<? extends Number> collection) { 678 if (collection instanceof LongArrayAsList) { 679 return ((LongArrayAsList) collection).toLongArray(); 680 } 681 682 Object[] boxedArray = collection.toArray(); 683 int len = boxedArray.length; 684 long[] array = new long[len]; 685 for (int i = 0; i < len; i++) { 686 // checkNotNull for GWT (do not optimize) 687 array[i] = ((Number) checkNotNull(boxedArray[i])).longValue(); 688 } 689 return array; 690 } 691 692 /** 693 * Returns a fixed-size list backed by the specified array, similar to {@link 694 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to 695 * set a value to {@code null} will result in a {@link NullPointerException}. 696 * 697 * <p>The returned list maintains the values, but not the identities, of {@code Long} objects 698 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for 699 * the returned list is unspecified. 700 * 701 * <p>The returned list is serializable. 702 * 703 * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableLongArray} 704 * instead, which has an {@link ImmutableLongArray#asList asList} view. 705 * 706 * @param backingArray the array to back the list 707 * @return a list view of the array 708 */ 709 public static List<Long> asList(long... backingArray) { 710 if (backingArray.length == 0) { 711 return Collections.emptyList(); 712 } 713 return new LongArrayAsList(backingArray); 714 } 715 716 @GwtCompatible 717 private static class LongArrayAsList extends AbstractList<Long> 718 implements RandomAccess, Serializable { 719 final long[] array; 720 final int start; 721 final int end; 722 723 LongArrayAsList(long[] array) { 724 this(array, 0, array.length); 725 } 726 727 LongArrayAsList(long[] array, int start, int end) { 728 this.array = array; 729 this.start = start; 730 this.end = end; 731 } 732 733 @Override 734 public int size() { 735 return end - start; 736 } 737 738 @Override 739 public boolean isEmpty() { 740 return false; 741 } 742 743 @Override 744 public Long get(int index) { 745 checkElementIndex(index, size()); 746 return array[start + index]; 747 } 748 749 @Override 750 public boolean contains(@CheckForNull Object target) { 751 // Overridden to prevent a ton of boxing 752 return (target instanceof Long) && Longs.indexOf(array, (Long) target, start, end) != -1; 753 } 754 755 @Override 756 public int indexOf(@CheckForNull Object target) { 757 // Overridden to prevent a ton of boxing 758 if (target instanceof Long) { 759 int i = Longs.indexOf(array, (Long) target, start, end); 760 if (i >= 0) { 761 return i - start; 762 } 763 } 764 return -1; 765 } 766 767 @Override 768 public int lastIndexOf(@CheckForNull Object target) { 769 // Overridden to prevent a ton of boxing 770 if (target instanceof Long) { 771 int i = Longs.lastIndexOf(array, (Long) target, start, end); 772 if (i >= 0) { 773 return i - start; 774 } 775 } 776 return -1; 777 } 778 779 @Override 780 public Long set(int index, Long element) { 781 checkElementIndex(index, size()); 782 long oldValue = array[start + index]; 783 // checkNotNull for GWT (do not optimize) 784 array[start + index] = checkNotNull(element); 785 return oldValue; 786 } 787 788 @Override 789 public List<Long> subList(int fromIndex, int toIndex) { 790 int size = size(); 791 checkPositionIndexes(fromIndex, toIndex, size); 792 if (fromIndex == toIndex) { 793 return Collections.emptyList(); 794 } 795 return new LongArrayAsList(array, start + fromIndex, start + toIndex); 796 } 797 798 @Override 799 public boolean equals(@CheckForNull Object object) { 800 if (object == this) { 801 return true; 802 } 803 if (object instanceof LongArrayAsList) { 804 LongArrayAsList that = (LongArrayAsList) object; 805 int size = size(); 806 if (that.size() != size) { 807 return false; 808 } 809 for (int i = 0; i < size; i++) { 810 if (array[start + i] != that.array[that.start + i]) { 811 return false; 812 } 813 } 814 return true; 815 } 816 return super.equals(object); 817 } 818 819 @Override 820 public int hashCode() { 821 int result = 1; 822 for (int i = start; i < end; i++) { 823 result = 31 * result + Longs.hashCode(array[i]); 824 } 825 return result; 826 } 827 828 @Override 829 public String toString() { 830 StringBuilder builder = new StringBuilder(size() * 10); 831 builder.append('[').append(array[start]); 832 for (int i = start + 1; i < end; i++) { 833 builder.append(", ").append(array[i]); 834 } 835 return builder.append(']').toString(); 836 } 837 838 long[] toLongArray() { 839 return Arrays.copyOfRange(array, start, end); 840 } 841 842 private static final long serialVersionUID = 0; 843 } 844}