Source code

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 java.util.Spliterator;
034import java.util.Spliterators;
035import javax.annotation.CheckForNull;
036
037/**
038 * Static utility methods pertaining to {@code int} primitives, that are not already found in either
039 * {@link Integer} or {@link Arrays}.
040 *
041 * <p>See the Guava User Guide article on <a
042 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
043 *
044 * @author Kevin Bourrillion
045 * @since 1.0
046 */
047@GwtCompatible(emulated = true)
048@ElementTypesAreNonnullByDefault
049public final class Ints extends IntsMethodsForWeb {
050  private Ints() {}
051
052  /**
053   * The number of bytes required to represent a primitive {@code int} value.
054   *
055   * <p><b>Java 8 users:</b> use {@link Integer#BYTES} instead.
056   */
057  public static final int BYTES = Integer.SIZE / Byte.SIZE;
058
059  /**
060   * The largest power of two that can be represented as an {@code int}.
061   *
062   * @since 10.0
063   */
064  public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
065
066  /**
067   * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Integer)
068   * value).hashCode()}.
069   *
070   * <p><b>Java 8 users:</b> use {@link Integer#hashCode(int)} instead.
071   *
072   * @param value a primitive {@code int} value
073   * @return a hash code for the value
074   */
075  public static int hashCode(int value) {
076    return value;
077  }
078
079  /**
080   * Returns the {@code int} value that is equal to {@code value}, if possible.
081   *
082   * @param value any value in the range of the {@code int} type
083   * @return the {@code int} value that equals {@code value}
084   * @throws IllegalArgumentException if {@code value} is greater than {@link Integer#MAX_VALUE} or
085   *     less than {@link Integer#MIN_VALUE}
086   */
087  public static int checkedCast(long value) {
088    int result = (int) value;
089    checkArgument(result == value, "Out of range: %s", value);
090    return result;
091  }
092
093  /**
094   * Returns the {@code int} nearest in value to {@code value}.
095   *
096   * @param value any {@code long} value
097   * @return the same value cast to {@code int} if it is in the range of the {@code int} type,
098   *     {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too
099   *     small
100   */
101  public static int saturatedCast(long value) {
102    if (value > Integer.MAX_VALUE) {
103      return Integer.MAX_VALUE;
104    }
105    if (value < Integer.MIN_VALUE) {
106      return Integer.MIN_VALUE;
107    }
108    return (int) value;
109  }
110
111  /**
112   * Compares the two specified {@code int} values. The sign of the value returned is the same as
113   * that of {@code ((Integer) a).compareTo(b)}.
114   *
115   * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
116   * equivalent {@link Integer#compare} method instead.
117   *
118   * @param a the first {@code int} to compare
119   * @param b the second {@code int} to compare
120   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
121   *     greater than {@code b}; or zero if they are equal
122   */
123  public static int compare(int a, int b) {
124    return (a < b) ? -1 : ((a > b) ? 1 : 0);
125  }
126
127  /**
128   * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
129   *
130   * @param array an array of {@code int} values, possibly empty
131   * @param target a primitive {@code int} value
132   * @return {@code true} if {@code array[i] == target} for some value of {@code i}
133   */
134  public static boolean contains(int[] array, int target) {
135    for (int value : array) {
136      if (value == target) {
137        return true;
138      }
139    }
140    return false;
141  }
142
143  /**
144   * Returns the index of the first appearance of the value {@code target} in {@code array}.
145   *
146   * @param array an array of {@code int} values, possibly empty
147   * @param target a primitive {@code int} value
148   * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
149   *     such index exists.
150   */
151  public static int indexOf(int[] array, int target) {
152    return indexOf(array, target, 0, array.length);
153  }
154
155  // TODO(kevinb): consider making this public
156  private static int indexOf(int[] array, int target, int start, int end) {
157    for (int i = start; i < end; i++) {
158      if (array[i] == target) {
159        return i;
160      }
161    }
162    return -1;
163  }
164
165  /**
166   * Returns the start position of the first occurrence of the specified {@code target} within
167   * {@code array}, or {@code -1} if there is no such occurrence.
168   *
169   * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
170   * i, i + target.length)} contains exactly the same elements as {@code target}.
171   *
172   * @param array the array to search for the sequence {@code target}
173   * @param target the array to search for as a sub-sequence of {@code array}
174   */
175  public static int indexOf(int[] array, int[] target) {
176    checkNotNull(array, "array");
177    checkNotNull(target, "target");
178    if (target.length == 0) {
179      return 0;
180    }
181
182    outer:
183    for (int i = 0; i < array.length - target.length + 1; i++) {
184      for (int j = 0; j < target.length; j++) {
185        if (array[i + j] != target[j]) {
186          continue outer;
187        }
188      }
189      return i;
190    }
191    return -1;
192  }
193
194  /**
195   * Returns the index of the last appearance of the value {@code target} in {@code array}.
196   *
197   * @param array an array of {@code int} values, possibly empty
198   * @param target a primitive {@code int} value
199   * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
200   *     such index exists.
201   */
202  public static int lastIndexOf(int[] array, int target) {
203    return lastIndexOf(array, target, 0, array.length);
204  }
205
206  // TODO(kevinb): consider making this public
207  private static int lastIndexOf(int[] array, int target, int start, int end) {
208    for (int i = end - 1; i >= start; i--) {
209      if (array[i] == target) {
210        return i;
211      }
212    }
213    return -1;
214  }
215
216  /**
217   * Returns the least value present in {@code array}.
218   *
219   * @param array a <i>nonempty</i> array of {@code int} values
220   * @return the value present in {@code array} that is less than or equal to every other value in
221   *     the array
222   * @throws IllegalArgumentException if {@code array} is empty
223   */
224  @GwtIncompatible(
225      "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
226  public static int min(int... array) {
227    checkArgument(array.length > 0);
228    int min = array[0];
229    for (int i = 1; i < array.length; i++) {
230      if (array[i] < min) {
231        min = array[i];
232      }
233    }
234    return min;
235  }
236
237  /**
238   * Returns the greatest value present in {@code array}.
239   *
240   * @param array a <i>nonempty</i> array of {@code int} values
241   * @return the value present in {@code array} that is greater than or equal to every other value
242   *     in the array
243   * @throws IllegalArgumentException if {@code array} is empty
244   */
245  @GwtIncompatible(
246      "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
247  public static int max(int... array) {
248    checkArgument(array.length > 0);
249    int max = array[0];
250    for (int i = 1; i < array.length; i++) {
251      if (array[i] > max) {
252        max = array[i];
253      }
254    }
255    return max;
256  }
257
258  /**
259   * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
260   *
261   * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
262   * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
263   * value} is greater than {@code max}, {@code max} is returned.
264   *
265   * @param value the {@code int} value to constrain
266   * @param min the lower bound (inclusive) of the range to constrain {@code value} to
267   * @param max the upper bound (inclusive) of the range to constrain {@code value} to
268   * @throws IllegalArgumentException if {@code min > max}
269   * @since 21.0
270   */
271  public static int constrainToRange(int value, int min, int max) {
272    checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
273    return Math.min(Math.max(value, min), max);
274  }
275
276  /**
277   * Returns the values from each provided array combined into a single array. For example, {@code
278   * concat(new int[] {a, b}, new int[] {}, new int[] {c}} returns the array {@code {a, b, c}}.
279   *
280   * @param arrays zero or more {@code int} arrays
281   * @return a single array containing all the values from the source arrays, in order
282   */
283  public static int[] concat(int[]... arrays) {
284    int length = 0;
285    for (int[] array : arrays) {
286      length += array.length;
287    }
288    int[] result = new int[length];
289    int pos = 0;
290    for (int[] array : arrays) {
291      System.arraycopy(array, 0, result, pos, array.length);
292      pos += array.length;
293    }
294    return result;
295  }
296
297  /**
298   * Returns a big-endian representation of {@code value} in a 4-element byte array; equivalent to
299   * {@code ByteBuffer.allocate(4).putInt(value).array()}. For example, the input value {@code
300   * 0x12131415} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15}}.
301   *
302   * <p>If you need to convert and concatenate several values (possibly even of different types),
303   * use a shared {@link java.nio.ByteBuffer} instance, or use {@link
304   * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
305   */
306  public static byte[] toByteArray(int value) {
307    return new byte[] {
308      (byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) value
309    };
310  }
311
312  /**
313   * Returns the {@code int} value whose big-endian representation is stored in the first 4 bytes of
314   * {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getInt()}. For example, the input
315   * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
316   * 0x12131415}.
317   *
318   * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
319   * flexibility at little cost in readability.
320   *
321   * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
322   */
323  public static int fromByteArray(byte[] bytes) {
324    checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
325    return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
326  }
327
328  /**
329   * Returns the {@code int} value whose byte representation is the given 4 bytes, in big-endian
330   * order; equivalent to {@code Ints.fromByteArray(new byte[] {b1, b2, b3, b4})}.
331   *
332   * @since 7.0
333   */
334  public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
335    return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
336  }
337
338  private static final class IntConverter extends Converter<String, Integer>
339      implements Serializable {
340    static final IntConverter INSTANCE = new IntConverter();
341
342    @Override
343    protected Integer doForward(String value) {
344      return Integer.decode(value);
345    }
346
347    @Override
348    protected String doBackward(Integer value) {
349      return value.toString();
350    }
351
352    @Override
353    public String toString() {
354      return "Ints.stringConverter()";
355    }
356
357    private Object readResolve() {
358      return INSTANCE;
359    }
360
361    private static final long serialVersionUID = 1;
362  }
363
364  /**
365   * Returns a serializable converter object that converts between strings and integers using {@link
366   * Integer#decode} and {@link Integer#toString()}. The returned converter throws {@link
367   * NumberFormatException} if the input string is invalid.
368   *
369   * <p><b>Warning:</b> please see {@link Integer#decode} to understand exactly how strings are
370   * parsed. For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the
371   * value {@code 83}.
372   *
373   * @since 16.0
374   */
375  public static Converter<String, Integer> stringConverter() {
376    return IntConverter.INSTANCE;
377  }
378
379  /**
380   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
381   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
382   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
383   * returned, containing the values of {@code array}, and zeroes in the remaining places.
384   *
385   * @param array the source array
386   * @param minLength the minimum length the returned array must guarantee
387   * @param padding an extra amount to "grow" the array by if growth is necessary
388   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
389   * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
390   *     minLength}
391   */
392  public static int[] ensureCapacity(int[] array, int minLength, int padding) {
393    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
394    checkArgument(padding >= 0, "Invalid padding: %s", padding);
395    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
396  }
397
398  /**
399   * Returns a string containing the supplied {@code int} values separated by {@code separator}. For
400   * example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
401   *
402   * @param separator the text that should appear between consecutive values in the resulting string
403   *     (but not at the start or end)
404   * @param array an array of {@code int} values, possibly empty
405   */
406  public static String join(String separator, int... array) {
407    checkNotNull(separator);
408    if (array.length == 0) {
409      return "";
410    }
411
412    // For pre-sizing a builder, just get the right order of magnitude
413    StringBuilder builder = new StringBuilder(array.length * 5);
414    builder.append(array[0]);
415    for (int i = 1; i < array.length; i++) {
416      builder.append(separator).append(array[i]);
417    }
418    return builder.toString();
419  }
420
421  /**
422   * Returns a comparator that compares two {@code int} arrays <a
423   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
424   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
425   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
426   * example, {@code [] < [1] < [1, 2] < [2]}.
427   *
428   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
429   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
430   *
431   * @since 2.0
432   */
433  public static Comparator<int[]> lexicographicalComparator() {
434    return LexicographicalComparator.INSTANCE;
435  }
436
437  private enum LexicographicalComparator implements Comparator<int[]> {
438    INSTANCE;
439
440    @Override
441    public int compare(int[] left, int[] right) {
442      int minLength = Math.min(left.length, right.length);
443      for (int i = 0; i < minLength; i++) {
444        int result = Ints.compare(left[i], right[i]);
445        if (result != 0) {
446          return result;
447        }
448      }
449      return left.length - right.length;
450    }
451
452    @Override
453    public String toString() {
454      return "Ints.lexicographicalComparator()";
455    }
456  }
457
458  /**
459   * Sorts the elements of {@code array} in descending order.
460   *
461   * @since 23.1
462   */
463  public static void sortDescending(int[] array) {
464    checkNotNull(array);
465    sortDescending(array, 0, array.length);
466  }
467
468  /**
469   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
470   * exclusive in descending order.
471   *
472   * @since 23.1
473   */
474  public static void sortDescending(int[] array, int fromIndex, int toIndex) {
475    checkNotNull(array);
476    checkPositionIndexes(fromIndex, toIndex, array.length);
477    Arrays.sort(array, fromIndex, toIndex);
478    reverse(array, fromIndex, toIndex);
479  }
480
481  /**
482   * Reverses the elements of {@code array}. This is equivalent to {@code
483   * Collections.reverse(Ints.asList(array))}, but is likely to be more efficient.
484   *
485   * @since 23.1
486   */
487  public static void reverse(int[] array) {
488    checkNotNull(array);
489    reverse(array, 0, array.length);
490  }
491
492  /**
493   * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
494   * exclusive. This is equivalent to {@code
495   * Collections.reverse(Ints.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
496   * efficient.
497   *
498   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
499   *     {@code toIndex > fromIndex}
500   * @since 23.1
501   */
502  public static void reverse(int[] array, int fromIndex, int toIndex) {
503    checkNotNull(array);
504    checkPositionIndexes(fromIndex, toIndex, array.length);
505    for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
506      int tmp = array[i];
507      array[i] = array[j];
508      array[j] = tmp;
509    }
510  }
511
512  /**
513   * Performs a right rotation of {@code array} of "distance" places, so that the first element is
514   * moved to index "distance", and the element at index {@code i} ends up at index {@code (distance
515   * + i) mod array.length}. This is equivalent to {@code Collections.rotate(Ints.asList(array),
516   * distance)}, but is considerably faster and avoids allocation and garbage collection.
517   *
518   * <p>The provided "distance" may be negative, which will rotate left.
519   *
520   * @since 32.0.0
521   */
522  public static void rotate(int[] array, int distance) {
523    rotate(array, distance, 0, array.length);
524  }
525
526  /**
527   * Performs a right rotation of {@code array} between {@code fromIndex} inclusive and {@code
528   * toIndex} exclusive. This is equivalent to {@code
529   * Collections.rotate(Ints.asList(array).subList(fromIndex, toIndex), distance)}, but is
530   * considerably faster and avoids allocations and garbage collection.
531   *
532   * <p>The provided "distance" may be negative, which will rotate left.
533   *
534   * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
535   *     {@code toIndex > fromIndex}
536   * @since 32.0.0
537   */
538  public static void rotate(int[] array, int distance, int fromIndex, int toIndex) {
539    // There are several well-known algorithms for rotating part of an array (or, equivalently,
540    // exchanging two blocks of memory). This classic text by Gries and Mills mentions several:
541    // https://ecommons.cornell.edu/bitstream/handle/1813/6292/81-452.pdf.
542    // (1) "Reversal", the one we have here.
543    // (2) "Dolphin". If we're rotating an array a of size n by a distance of d, then element a[0]
544    //     ends up at a[d], which in turn ends up at a[2d], and so on until we get back to a[0].
545    //     (All indices taken mod n.) If d and n are mutually prime, all elements will have been
546    //     moved at that point. Otherwise, we can rotate the cycle a[1], a[1 + d], a[1 + 2d], etc,
547    //     then a[2] etc, and so on until we have rotated all elements. There are gcd(d, n) cycles
548    //     in all.
549    // (3) "Successive". We can consider that we are exchanging a block of size d (a[0..d-1]) with a
550    //     block of size n-d (a[d..n-1]), where in general these blocks have different sizes. If we
551    //     imagine a line separating the first block from the second, we can proceed by exchanging
552    //     the smaller of these blocks with the far end of the other one. That leaves us with a
553    //     smaller version of the same problem.
554    //     Say we are rotating abcdefgh by 5. We start with abcde|fgh. The smaller block is [fgh]:
555    //     [abc]de|[fgh] -> [fgh]de|[abc]. Now [fgh] is in the right place, but we need to swap [de]
556    //     with [abc]: fgh[de]|a[bc] -> fgh[bc]|a[de]. Now we need to swap [a] with [bc]:
557    //     fgh[b]c|[a]de -> fgh[a]c|[b]de. Finally we need to swap [c] with [b]:
558    //     fgha[c]|[b]de -> fgha[b]|[c]de. Because these two blocks are the same size, we are done.
559    // The Dolphin algorithm is attractive because it does the fewest array reads and writes: each
560    // array slot is read and written exactly once. However, it can have very poor memory locality:
561    // benchmarking shows it can take 7 times longer than the other two in some cases. The other two
562    // do n swaps, minus a delta (0 or 2 for Reversal, gcd(d, n) for Successive), so that's about
563    // twice as many reads and writes. But benchmarking shows that they usually perform better than
564    // Dolphin. Reversal is about as good as Successive on average, and it is much simpler,
565    // especially since we already have a `reverse` method.
566    checkNotNull(array);
567    checkPositionIndexes(fromIndex, toIndex, array.length);
568    if (array.length <= 1) {
569      return;
570    }
571
572    int length = toIndex - fromIndex;
573    // Obtain m = (-distance mod length), a non-negative value less than "length". This is how many
574    // places left to rotate.
575    int m = -distance % length;
576    m = (m < 0) ? m + length : m;
577    // The current index of what will become the first element of the rotated section.
578    int newFirstIndex = m + fromIndex;
579    if (newFirstIndex == fromIndex) {
580      return;
581    }
582
583    reverse(array, fromIndex, newFirstIndex);
584    reverse(array, newFirstIndex, toIndex);
585    reverse(array, fromIndex, toIndex);
586  }
587
588  /**
589   * Returns an array containing each value of {@code collection}, converted to a {@code int} value
590   * in the manner of {@link Number#intValue}.
591   *
592   * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
593   * Calling this method is as thread-safe as calling that method.
594   *
595   * @param collection a collection of {@code Number} instances
596   * @return an array containing the same values as {@code collection}, in the same order, converted
597   *     to primitives
598   * @throws NullPointerException if {@code collection} or any of its elements is null
599   * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0)
600   */
601  public static int[] toArray(Collection<? extends Number> collection) {
602    if (collection instanceof IntArrayAsList) {
603      return ((IntArrayAsList) collection).toIntArray();
604    }
605
606    Object[] boxedArray = collection.toArray();
607    int len = boxedArray.length;
608    int[] array = new int[len];
609    for (int i = 0; i < len; i++) {
610      // checkNotNull for GWT (do not optimize)
611      array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
612    }
613    return array;
614  }
615
616  /**
617   * Returns a fixed-size list backed by the specified array, similar to {@link
618   * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
619   * set a value to {@code null} will result in a {@link NullPointerException}.
620   *
621   * <p>The returned list maintains the values, but not the identities, of {@code Integer} objects
622   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
623   * the returned list is unspecified.
624   *
625   * <p>The returned list is serializable.
626   *
627   * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableIntArray}
628   * instead, which has an {@link ImmutableIntArray#asList asList} view.
629   *
630   * @param backingArray the array to back the list
631   * @return a list view of the array
632   */
633  public static List<Integer> asList(int... backingArray) {
634    if (backingArray.length == 0) {
635      return Collections.emptyList();
636    }
637    return new IntArrayAsList(backingArray);
638  }
639
640  @GwtCompatible
641  private static class IntArrayAsList extends AbstractList<Integer>
642      implements RandomAccess, Serializable {
643    final int[] array;
644    final int start;
645    final int end;
646
647    IntArrayAsList(int[] array) {
648      this(array, 0, array.length);
649    }
650
651    IntArrayAsList(int[] array, int start, int end) {
652      this.array = array;
653      this.start = start;
654      this.end = end;
655    }
656
657    @Override
658    public int size() {
659      return end - start;
660    }
661
662    @Override
663    public boolean isEmpty() {
664      return false;
665    }
666
667    @Override
668    public Integer get(int index) {
669      checkElementIndex(index, size());
670      return array[start + index];
671    }
672
673    @Override
674    public Spliterator.OfInt spliterator() {
675      return Spliterators.spliterator(array, start, end, 0);
676    }
677
678    @Override
679    public boolean contains(@CheckForNull Object target) {
680      // Overridden to prevent a ton of boxing
681      return (target instanceof Integer) && Ints.indexOf(array, (Integer) target, start, end) != -1;
682    }
683
684    @Override
685    public int indexOf(@CheckForNull Object target) {
686      // Overridden to prevent a ton of boxing
687      if (target instanceof Integer) {
688        int i = Ints.indexOf(array, (Integer) target, start, end);
689        if (i >= 0) {
690          return i - start;
691        }
692      }
693      return -1;
694    }
695
696    @Override
697    public int lastIndexOf(@CheckForNull Object target) {
698      // Overridden to prevent a ton of boxing
699      if (target instanceof Integer) {
700        int i = Ints.lastIndexOf(array, (Integer) target, start, end);
701        if (i >= 0) {
702          return i - start;
703        }
704      }
705      return -1;
706    }
707
708    @Override
709    public Integer set(int index, Integer element) {
710      checkElementIndex(index, size());
711      int oldValue = array[start + index];
712      // checkNotNull for GWT (do not optimize)
713      array[start + index] = checkNotNull(element);
714      return oldValue;
715    }
716
717    @Override
718    public List<Integer> subList(int fromIndex, int toIndex) {
719      int size = size();
720      checkPositionIndexes(fromIndex, toIndex, size);
721      if (fromIndex == toIndex) {
722        return Collections.emptyList();
723      }
724      return new IntArrayAsList(array, start + fromIndex, start + toIndex);
725    }
726
727    @Override
728    public boolean equals(@CheckForNull Object object) {
729      if (object == this) {
730        return true;
731      }
732      if (object instanceof IntArrayAsList) {
733        IntArrayAsList that = (IntArrayAsList) object;
734        int size = size();
735        if (that.size() != size) {
736          return false;
737        }
738        for (int i = 0; i < size; i++) {
739          if (array[start + i] != that.array[that.start + i]) {
740            return false;
741          }
742        }
743        return true;
744      }
745      return super.equals(object);
746    }
747
748    @Override
749    public int hashCode() {
750      int result = 1;
751      for (int i = start; i < end; i++) {
752        result = 31 * result + Ints.hashCode(array[i]);
753      }
754      return result;
755    }
756
757    @Override
758    public String toString() {
759      StringBuilder builder = new StringBuilder(size() * 5);
760      builder.append('[').append(array[start]);
761      for (int i = start + 1; i < end; i++) {
762        builder.append(", ").append(array[i]);
763      }
764      return builder.append(']').toString();
765    }
766
767    int[] toIntArray() {
768      return Arrays.copyOfRange(array, start, end);
769    }
770
771    private static final long serialVersionUID = 0;
772  }
773
774  /**
775   * Parses the specified string as a signed decimal integer value. The ASCII character {@code '-'}
776   * (<code>'&#92;u002D'</code>) is recognized as the minus sign.
777   *
778   * <p>Unlike {@link Integer#parseInt(String)}, this method returns {@code null} instead of
779   * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
780   * and returns {@code null} if non-ASCII digits are present in the string.
781   *
782   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
783   * the change to {@link Integer#parseInt(String)} for that version.
784   *
785   * @param string the string representation of an integer value
786   * @return the integer value represented by {@code string}, or {@code null} if {@code string} has
787   *     a length of zero or cannot be parsed as an integer value
788   * @throws NullPointerException if {@code string} is {@code null}
789   * @since 11.0
790   */
791  @CheckForNull
792  public static Integer tryParse(String string) {
793    return tryParse(string, 10);
794  }
795
796  /**
797   * Parses the specified string as a signed integer value using the specified radix. The ASCII
798   * character {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
799   *
800   * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns {@code null} instead of
801   * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
802   * and returns {@code null} if non-ASCII digits are present in the string.
803   *
804   * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
805   * the change to {@link Integer#parseInt(String, int)} for that version.
806   *
807   * @param string the string representation of an integer value
808   * @param radix the radix to use when parsing
809   * @return the integer value represented by {@code string} using {@code radix}, or {@code null} if
810   *     {@code string} has a length of zero or cannot be parsed as an integer value
811   * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix >
812   *     Character.MAX_RADIX}
813   * @throws NullPointerException if {@code string} is {@code null}
814   * @since 19.0
815   */
816  @CheckForNull
817  public static Integer tryParse(String string, int radix) {
818    Long result = Longs.tryParse(string, radix);
819    if (result == null || result.longValue() != result.intValue()) {
820      return null;
821    } else {
822      return result.intValue();
823    }
824  }
825}