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 java.util.Spliterator;
033import java.util.Spliterators;
034import javax.annotation.CheckForNull;
035
036/**
037 * Static utility methods pertaining to {@code long} primitives, that are not already found in
038 * either {@link Long} or {@link Arrays}.
039 *
040 * <p>See the Guava User Guide article on <a
041 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
042 *
043 * @author Kevin Bourrillion
044 * @since 1.0
045 */
046@GwtCompatible
047@ElementTypesAreNonnullByDefault
048public final class Longs {
049  private Longs() {}
050
051  /**
052   * The number of bytes required to represent a primitive {@code long} value.
053   *
054   * <p><b>Java 8 users:</b> use {@link Long#BYTES} instead.
055   */
056  public static final int BYTES = Long.SIZE / Byte.SIZE;
057
058  /**
059   * The largest power of two that can be represented as a {@code long}.
060   *
061   * @since 10.0
062   */
063  public static final long MAX_POWER_OF_TWO = 1L << (Long.SIZE - 2);
064
065  /**
066   * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Long)
067   * value).hashCode()}.
068   *
069   * <p>This method always return the value specified by {@link Long#hashCode()} in java, which
070   * might be different from {@code ((Long) value).hashCode()} in GWT because {@link
071   * Long#hashCode()} in GWT does not obey the JRE contract.
072   *
073   * <p><b>Java 8 users:</b> use {@link Long#hashCode(long)} instead.
074   *
075   * @param value a primitive {@code long} value
076   * @return a hash code for the value
077   */
078  public static int hashCode(long value) {
079    return (int) (value ^ (value >>> 32));
080  }
081
082  /**
083   * Compares the two specified {@code long} values. The sign of the value returned is the same as
084   * that of {@code ((Long) a).compareTo(b)}.
085   *
086   * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
087   * equivalent {@link Long#compare} method instead.
088   *
089   * @param a the first {@code long} to compare
090   * @param b the second {@code long} to compare
091   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
092   *     greater than {@code b}; or zero if they are equal
093   */
094  public static int compare(long a, long b) {
095    return (a < b) ? -1 : ((a > b) ? 1 : 0);
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   */
250  public static long[] concat(long[]... arrays) {
251    int length = 0;
252    for (long[] array : arrays) {
253      length += array.length;
254    }
255    long[] result = new long[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  /**
265   * Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to
266   * {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value {@code
267   * 0x1213141516171819L} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
268   * 0x18, 0x19}}.
269   *
270   * <p>If you need to convert and concatenate several values (possibly even of different types),
271   * use a shared {@link java.nio.ByteBuffer} instance, or use {@link
272   * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
273   */
274  public static byte[] toByteArray(long value) {
275    // Note that this code needs to stay compatible with GWT, which has known
276    // bugs when narrowing byte casts of long values occur.
277    byte[] result = new byte[8];
278    for (int i = 7; i >= 0; i--) {
279      result[i] = (byte) (value & 0xffL);
280      value >>= 8;
281    }
282    return result;
283  }
284
285  /**
286   * Returns the {@code long} value whose big-endian representation is stored in the first 8 bytes
287   * of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getLong()}. For example, the
288   * input byte array {@code {0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19}} would yield the
289   * {@code long} value {@code 0x1213141516171819L}.
290   *
291   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
292   * flexibility at little cost in readability.
293   *
294   * @throws IllegalArgumentException if {@code bytes} has fewer than 8 elements
295   */
296  public static long fromByteArray(byte[] bytes) {
297    checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
298    return fromBytes(
299        bytes[0], bytes[1], bytes[2], bytes[3], bytes[4], bytes[5], bytes[6], bytes[7]);
300  }
301
302  /**
303   * Returns the {@code long} value whose byte representation is the given 8 bytes, in big-endian
304   * order; equivalent to {@code Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8})}.
305   *
306   * @since 7.0
307   */
308  public static long fromBytes(
309      byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8) {
310    return (b1 & 0xFFL) << 56
311        | (b2 & 0xFFL) << 48
312        | (b3 & 0xFFL) << 40
313        | (b4 & 0xFFL) << 32
314        | (b5 & 0xFFL) << 24
315        | (b6 & 0xFFL) << 16
316        | (b7 & 0xFFL) << 8
317        | (b8 & 0xFFL);
318  }
319
320  /*
321   * Moving asciiDigits into this static holder class lets ProGuard eliminate and inline the Longs
322   * class.
323   */
324  static final class AsciiDigits {
325    private AsciiDigits() {}
326
327    private static final byte[] asciiDigits;
328
329    static {
330      byte[] result = new byte[128];
331      Arrays.fill(result, (byte) -1);
332      for (int i = 0; i < 10; i++) {
333        result['0' + i] = (byte) i;
334      }
335      for (int i = 0; i < 26; i++) {
336        result['A' + i] = (byte) (10 + i);
337        result['a' + i] = (byte) (10 + i);
338      }
339      asciiDigits = result;
340    }
341
342    static int digit(char c) {
343      return (c < 128) ? asciiDigits[c] : -1;
344    }
345  }
346
347  /**
348   * Parses the specified string as a signed decimal long value. The ASCII character {@code '-'} (
349   * <code>'&#92;u002D'</code>) is recognized as the minus sign.
350   *
351   * <p>Unlike {@link Long#parseLong(String)}, this method returns {@code null} instead of throwing
352   * an exception if parsing fails. Additionally, this method only accepts ASCII digits, and returns
353   * {@code null} if non-ASCII digits are present in the string.
354   *
355   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
356   * the change to {@link Long#parseLong(String)} for that version.
357   *
358   * @param string the string representation of a long value
359   * @return the long value represented by {@code string}, or {@code null} if {@code string} has a
360   *     length of zero or cannot be parsed as a long value
361   * @throws NullPointerException if {@code string} is {@code null}
362   * @since 14.0
363   */
364  @CheckForNull
365  public static Long tryParse(String string) {
366    return tryParse(string, 10);
367  }
368
369  /**
370   * Parses the specified string as a signed long value using the specified radix. The ASCII
371   * character {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
372   *
373   * <p>Unlike {@link Long#parseLong(String, int)}, this method returns {@code null} instead of
374   * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
375   * and returns {@code null} if non-ASCII digits are present in the string.
376   *
377   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
378   * the change to {@link Long#parseLong(String, int)} for that version.
379   *
380   * @param string the string representation of a long value
381   * @param radix the radix to use when parsing
382   * @return the long value represented by {@code string} using {@code radix}, or {@code null} if
383   *     {@code string} has a length of zero or cannot be parsed as a long value
384   * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix >
385   *     Character.MAX_RADIX}
386   * @throws NullPointerException if {@code string} is {@code null}
387   * @since 19.0
388   */
389  @CheckForNull
390  public static Long tryParse(String string, int radix) {
391    if (checkNotNull(string).isEmpty()) {
392      return null;
393    }
394    if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
395      throw new IllegalArgumentException(
396          "radix must be between MIN_RADIX and MAX_RADIX but was " + radix);
397    }
398    boolean negative = string.charAt(0) == '-';
399    int index = negative ? 1 : 0;
400    if (index == string.length()) {
401      return null;
402    }
403    int digit = AsciiDigits.digit(string.charAt(index++));
404    if (digit < 0 || digit >= radix) {
405      return null;
406    }
407    long accum = -digit;
408
409    long cap = Long.MIN_VALUE / radix;
410
411    while (index < string.length()) {
412      digit = AsciiDigits.digit(string.charAt(index++));
413      if (digit < 0 || digit >= radix || accum < cap) {
414        return null;
415      }
416      accum *= radix;
417      if (accum < Long.MIN_VALUE + digit) {
418        return null;
419      }
420      accum -= digit;
421    }
422
423    if (negative) {
424      return accum;
425    } else if (accum == Long.MIN_VALUE) {
426      return null;
427    } else {
428      return -accum;
429    }
430  }
431
432  private static final class LongConverter extends Converter<String, Long> implements Serializable {
433    static final LongConverter INSTANCE = new LongConverter();
434
435    @Override
436    protected Long doForward(String value) {
437      return Long.decode(value);
438    }
439
440    @Override
441    protected String doBackward(Long value) {
442      return value.toString();
443    }
444
445    @Override
446    public String toString() {
447      return "Longs.stringConverter()";
448    }
449
450    private Object readResolve() {
451      return INSTANCE;
452    }
453
454    private static final long serialVersionUID = 1;
455  }
456
457  /**
458   * Returns a serializable converter object that converts between strings and longs using {@link
459   * Long#decode} and {@link Long#toString()}. The returned converter throws {@link
460   * NumberFormatException} if the input string is invalid.
461   *
462   * <p><b>Warning:</b> please see {@link Long#decode} to understand exactly how strings are parsed.
463   * For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the value
464   * {@code 83L}.
465   *
466   * @since 16.0
467   */
468  public static Converter<String, Long> stringConverter() {
469    return LongConverter.INSTANCE;
470  }
471
472  /**
473   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
474   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
475   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
476   * returned, containing the values of {@code array}, and zeroes in the remaining places.
477   *
478   * @param array the source array
479   * @param minLength the minimum length the returned array must guarantee
480   * @param padding an extra amount to "grow" the array by if growth is necessary
481   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
482   * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
483   *     minLength}
484   */
485  public static long[] ensureCapacity(long[] array, int minLength, int padding) {
486    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
487    checkArgument(padding >= 0, "Invalid padding: %s", padding);
488    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
489  }
490
491  /**
492   * Returns a string containing the supplied {@code long} values separated by {@code separator}.
493   * For example, {@code join("-", 1L, 2L, 3L)} returns the string {@code "1-2-3"}.
494   *
495   * @param separator the text that should appear between consecutive values in the resulting string
496   *     (but not at the start or end)
497   * @param array an array of {@code long} values, possibly empty
498   */
499  public static String join(String separator, long... array) {
500    checkNotNull(separator);
501    if (array.length == 0) {
502      return "";
503    }
504
505    // For pre-sizing a builder, just get the right order of magnitude
506    StringBuilder builder = new StringBuilder(array.length * 10);
507    builder.append(array[0]);
508    for (int i = 1; i < array.length; i++) {
509      builder.append(separator).append(array[i]);
510    }
511    return builder.toString();
512  }
513
514  /**
515   * Returns a comparator that compares two {@code long} arrays <a
516   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
517   * compares, using {@link #compare(long, long)}), the first pair of values that follow any common
518   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
519   * example, {@code [] < [1L] < [1L, 2L] < [2L]}.
520   *
521   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
522   * support only identity equality), but it is consistent with {@link Arrays#equals(long[],
523   * long[])}.
524   *
525   * @since 2.0
526   */
527  public static Comparator<long[]> lexicographicalComparator() {
528    return LexicographicalComparator.INSTANCE;
529  }
530
531  private enum LexicographicalComparator implements Comparator<long[]> {
532    INSTANCE;
533
534    @Override
535    public int compare(long[] left, long[] right) {
536      int minLength = Math.min(left.length, right.length);
537      for (int i = 0; i < minLength; i++) {
538        int result = Longs.compare(left[i], right[i]);
539        if (result != 0) {
540          return result;
541        }
542      }
543      return left.length - right.length;
544    }
545
546    @Override
547    public String toString() {
548      return "Longs.lexicographicalComparator()";
549    }
550  }
551
552  /**
553   * Sorts the elements of {@code array} in descending order.
554   *
555   * @since 23.1
556   */
557  public static void sortDescending(long[] array) {
558    checkNotNull(array);
559    sortDescending(array, 0, array.length);
560  }
561
562  /**
563   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
564   * exclusive in descending order.
565   *
566   * @since 23.1
567   */
568  public static void sortDescending(long[] array, int fromIndex, int toIndex) {
569    checkNotNull(array);
570    checkPositionIndexes(fromIndex, toIndex, array.length);
571    Arrays.sort(array, fromIndex, toIndex);
572    reverse(array, fromIndex, toIndex);
573  }
574
575  /**
576   * Reverses the elements of {@code array}. This is equivalent to {@code
577   * Collections.reverse(Longs.asList(array))}, but is likely to be more efficient.
578   *
579   * @since 23.1
580   */
581  public static void reverse(long[] array) {
582    checkNotNull(array);
583    reverse(array, 0, array.length);
584  }
585
586  /**
587   * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
588   * exclusive. This is equivalent to {@code
589   * Collections.reverse(Longs.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
590   * efficient.
591   *
592   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
593   *     {@code toIndex > fromIndex}
594   * @since 23.1
595   */
596  public static void reverse(long[] array, int fromIndex, int toIndex) {
597    checkNotNull(array);
598    checkPositionIndexes(fromIndex, toIndex, array.length);
599    for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
600      long tmp = array[i];
601      array[i] = array[j];
602      array[j] = tmp;
603    }
604  }
605
606  /**
607   * Performs a right rotation of {@code array} of "distance" places, so that the first element is
608   * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
609   * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Longs.asList(array),
610   * distance)}, but is considerably faster and avoids allocation and garbage collection.
611   *
612   * <p>The provided "distance" may be negative, which will rotate left.
613   *
614   * @since 32.0.0
615   */
616  public static void rotate(long[] array, int distance) {
617    rotate(array, distance, 0, array.length);
618  }
619
620  /**
621   * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code
622   * toIndex} exclusive. This is equivalent to {@code
623   * Collections.rotate(Longs.asList(array).subList(fromIndex, toIndex), distance)}, but is
624   * considerably faster and avoids allocations and garbage collection.
625   *
626   * <p>The provided "distance" may be negative, which will rotate left.
627   *
628   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
629   *     {@code toIndex > fromIndex}
630   * @since 32.0.0
631   */
632  public static void rotate(long[] array, int distance, int fromIndex, int toIndex) {
633    // See Ints.rotate for more details about possible algorithms here.
634    checkNotNull(array);
635    checkPositionIndexes(fromIndex, toIndex, array.length);
636    if (array.length <= 1) {
637      return;
638    }
639
640    int length = toIndex - fromIndex;
641    // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many
642    // places left to rotate.
643    int m = -distance % length;
644    m = (m < 0) ? m + length : m;
645    // The current index of what will become the first element of the rotated section.
646    int newFirstIndex = m + fromIndex;
647    if (newFirstIndex == fromIndex) {
648      return;
649    }
650
651    reverse(array, fromIndex, newFirstIndex);
652    reverse(array, newFirstIndex, toIndex);
653    reverse(array, fromIndex, toIndex);
654  }
655
656  /**
657   * Returns an array containing each value of {@code collection}, converted to a {@code long} value
658   * in the manner of {@link Number#longValue}.
659   *
660   * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
661   * Calling this method is as thread-safe as calling that method.
662   *
663   * @param collection a collection of {@code Number} instances
664   * @return an array containing the same values as {@code collection}, in the same order, converted
665   *     to primitives
666   * @throws NullPointerException if {@code collection} or any of its elements is null
667   * @since 1.0 (parameter was {@code Collection<Long>} before 12.0)
668   */
669  public static long[] toArray(Collection<? extends Number> collection) {
670    if (collection instanceof LongArrayAsList) {
671      return ((LongArrayAsList) collection).toLongArray();
672    }
673
674    Object[] boxedArray = collection.toArray();
675    int len = boxedArray.length;
676    long[] array = new long[len];
677    for (int i = 0; i < len; i++) {
678      // checkNotNull for GWT (do not optimize)
679      array[i] = ((Number) checkNotNull(boxedArray[i])).longValue();
680    }
681    return array;
682  }
683
684  /**
685   * Returns a fixed-size list backed by the specified array, similar to {@link
686   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
687   * set a value to {@code null} will result in a {@link NullPointerException}.
688   *
689   * <p>The returned list maintains the values, but not the identities, of {@code Long} objects
690   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
691   * the returned list is unspecified.
692   *
693   * <p>The returned list is serializable.
694   *
695   * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableLongArray}
696   * instead, which has an {@link ImmutableLongArray#asList asList} view.
697   *
698   * @param backingArray the array to back the list
699   * @return a list view of the array
700   */
701  public static List<Long> asList(long... backingArray) {
702    if (backingArray.length == 0) {
703      return Collections.emptyList();
704    }
705    return new LongArrayAsList(backingArray);
706  }
707
708  @GwtCompatible
709  private static class LongArrayAsList extends AbstractList<Long>
710      implements RandomAccess, Serializable {
711    final long[] array;
712    final int start;
713    final int end;
714
715    LongArrayAsList(long[] array) {
716      this(array, 0, array.length);
717    }
718
719    LongArrayAsList(long[] array, int start, int end) {
720      this.array = array;
721      this.start = start;
722      this.end = end;
723    }
724
725    @Override
726    public int size() {
727      return end - start;
728    }
729
730    @Override
731    public boolean isEmpty() {
732      return false;
733    }
734
735    @Override
736    public Long get(int index) {
737      checkElementIndex(index, size());
738      return array[start + index];
739    }
740
741    @Override
742    public Spliterator.OfLong spliterator() {
743      return Spliterators.spliterator(array, start, end, 0);
744    }
745
746    @Override
747    public boolean contains(@CheckForNull Object target) {
748      // Overridden to prevent a ton of boxing
749      return (target instanceof Long) && Longs.indexOf(array, (Long) target, start, end) != -1;
750    }
751
752    @Override
753    public int indexOf(@CheckForNull Object target) {
754      // Overridden to prevent a ton of boxing
755      if (target instanceof Long) {
756        int i = Longs.indexOf(array, (Long) target, start, end);
757        if (i >= 0) {
758          return i - start;
759        }
760      }
761      return -1;
762    }
763
764    @Override
765    public int lastIndexOf(@CheckForNull Object target) {
766      // Overridden to prevent a ton of boxing
767      if (target instanceof Long) {
768        int i = Longs.lastIndexOf(array, (Long) target, start, end);
769        if (i >= 0) {
770          return i - start;
771        }
772      }
773      return -1;
774    }
775
776    @Override
777    public Long set(int index, Long element) {
778      checkElementIndex(index, size());
779      long oldValue = array[start + index];
780      // checkNotNull for GWT (do not optimize)
781      array[start + index] = checkNotNull(element);
782      return oldValue;
783    }
784
785    @Override
786    public List<Long> subList(int fromIndex, int toIndex) {
787      int size = size();
788      checkPositionIndexes(fromIndex, toIndex, size);
789      if (fromIndex == toIndex) {
790        return Collections.emptyList();
791      }
792      return new LongArrayAsList(array, start + fromIndex, start + toIndex);
793    }
794
795    @Override
796    public boolean equals(@CheckForNull Object object) {
797      if (object == this) {
798        return true;
799      }
800      if (object instanceof LongArrayAsList) {
801        LongArrayAsList that = (LongArrayAsList) object;
802        int size = size();
803        if (that.size() != size) {
804          return false;
805        }
806        for (int i = 0; i < size; i++) {
807          if (array[start + i] != that.array[that.start + i]) {
808            return false;
809          }
810        }
811        return true;
812      }
813      return super.equals(object);
814    }
815
816    @Override
817    public int hashCode() {
818      int result = 1;
819      for (int i = start; i < end; i++) {
820        result = 31 * result + Longs.hashCode(array[i]);
821      }
822      return result;
823    }
824
825    @Override
826    public String toString() {
827      StringBuilder builder = new StringBuilder(size() * 10);
828      builder.append('[').append(array[start]);
829      for (int i = start + 1; i < end; i++) {
830        builder.append(", ").append(array[i]);
831      }
832      return builder.append(']').toString();
833    }
834
835    long[] toLongArray() {
836      return Arrays.copyOfRange(array, start, end);
837    }
838
839    private static final long serialVersionUID = 0;
840  }
841}