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1   /*
2    * Copyright (C) 2008 The Guava Authors
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5    * in compliance with the License. You may obtain a copy of the License at
6    *
7    * http://www.apache.org/licenses/LICENSE-2.0
8    *
9    * Unless required by applicable law or agreed to in writing, software distributed under the License
10   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11   * or implied. See the License for the specific language governing permissions and limitations under
12   * the License.
13   */
14  
15  package com.google.common.primitives;
16  
17  import static com.google.common.base.Preconditions.checkArgument;
18  import static com.google.common.base.Preconditions.checkElementIndex;
19  import static com.google.common.base.Preconditions.checkNotNull;
20  import static com.google.common.base.Preconditions.checkPositionIndexes;
21  
22  import com.google.common.annotations.Beta;
23  import com.google.common.annotations.GwtCompatible;
24  import com.google.common.base.Converter;
25  import java.io.Serializable;
26  import java.util.AbstractList;
27  import java.util.Arrays;
28  import java.util.Collection;
29  import java.util.Collections;
30  import java.util.Comparator;
31  import java.util.List;
32  import java.util.RandomAccess;
33  import java.util.Spliterator;
34  import java.util.Spliterators;
35  import javax.annotation.CheckForNull;
36  import javax.annotation.Nullable;
37  
38  /**
39   * Static utility methods pertaining to {@code int} primitives, that are not already found in either
40   * {@link Integer} or {@link Arrays}.
41   *
42   * <p>See the Guava User Guide article on
43   * <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
44   *
45   * @author Kevin Bourrillion
46   * @since 1.0
47   */
48  @GwtCompatible
49  public final class Ints {
50    private Ints() {}
51  
52    /**
53     * The number of bytes required to represent a primitive {@code int} value.
54     *
55     * <p><b>Java 8 users:</b> use {@link Integer#BYTES} instead.
56     */
57    public static final int BYTES = Integer.SIZE / Byte.SIZE;
58  
59    /**
60     * The largest power of two that can be represented as an {@code int}.
61     *
62     * @since 10.0
63     */
64    public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
65  
66    /**
67     * Returns a hash code for {@code value}; equal to the result of invoking
68     * {@code ((Integer) value).hashCode()}.
69     *
70     * <p><b>Java 8 users:</b> use {@link Integer#hashCode(int)} instead.
71     *
72     * @param value a primitive {@code int} value
73     * @return a hash code for the value
74     */
75    public static int hashCode(int value) {
76      return value;
77    }
78  
79    /**
80     * Returns the {@code int} value that is equal to {@code value}, if possible.
81     *
82     * @param value any value in the range of the {@code int} type
83     * @return the {@code int} value that equals {@code value}
84     * @throws IllegalArgumentException if {@code value} is greater than {@link Integer#MAX_VALUE} or
85     *     less than {@link Integer#MIN_VALUE}
86     */
87    public static int checkedCast(long value) {
88      int result = (int) value;
89      checkArgument(result == value, "Out of range: %s", value);
90      return result;
91    }
92  
93    /**
94     * Returns the {@code int} nearest in value to {@code value}.
95     *
96     * @param value any {@code long} value
97     * @return the same value cast to {@code int} if it is in the range of the {@code int} type,
98     *     {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too
99     *     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
133    *     i}
134    */
135   public static boolean contains(int[] array, int target) {
136     for (int value : array) {
137       if (value == target) {
138         return true;
139       }
140     }
141     return false;
142   }
143 
144   /**
145    * Returns the index of the first appearance of the value {@code target} in {@code array}.
146    *
147    * @param array an array of {@code int} values, possibly empty
148    * @param target a primitive {@code int} value
149    * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
150    *     such index exists.
151    */
152   public static int indexOf(int[] array, int target) {
153     return indexOf(array, target, 0, array.length);
154   }
155 
156   // TODO(kevinb): consider making this public
157   private static int indexOf(int[] array, int target, int start, int end) {
158     for (int i = start; i < end; i++) {
159       if (array[i] == target) {
160         return i;
161       }
162     }
163     return -1;
164   }
165 
166   /**
167    * Returns the start position of the first occurrence of the specified {@code
168    * target} within {@code array}, or {@code -1} if there is no such occurrence.
169    *
170    * <p>More formally, returns the lowest index {@code i} such that
171    * {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as
172    * {@code target}.
173    *
174    * @param array the array to search for the sequence {@code target}
175    * @param target the array to search for as a sub-sequence of {@code array}
176    */
177   public static int indexOf(int[] array, int[] target) {
178     checkNotNull(array, "array");
179     checkNotNull(target, "target");
180     if (target.length == 0) {
181       return 0;
182     }
183 
184     outer:
185     for (int i = 0; i < array.length - target.length + 1; i++) {
186       for (int j = 0; j < target.length; j++) {
187         if (array[i + j] != target[j]) {
188           continue outer;
189         }
190       }
191       return i;
192     }
193     return -1;
194   }
195 
196   /**
197    * Returns the index of the last appearance of the value {@code target} in {@code array}.
198    *
199    * @param array an array of {@code int} values, possibly empty
200    * @param target a primitive {@code int} value
201    * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
202    *     such index exists.
203    */
204   public static int lastIndexOf(int[] array, int target) {
205     return lastIndexOf(array, target, 0, array.length);
206   }
207 
208   // TODO(kevinb): consider making this public
209   private static int lastIndexOf(int[] array, int target, int start, int end) {
210     for (int i = end - 1; i >= start; i--) {
211       if (array[i] == target) {
212         return i;
213       }
214     }
215     return -1;
216   }
217 
218   /**
219    * Returns the least value present in {@code array}.
220    *
221    * @param array a <i>nonempty</i> array of {@code int} values
222    * @return the value present in {@code array} that is less than or equal to every other value in
223    *     the array
224    * @throws IllegalArgumentException if {@code array} is empty
225    */
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   public static int max(int... array) {
246     checkArgument(array.length > 0);
247     int max = array[0];
248     for (int i = 1; i < array.length; i++) {
249       if (array[i] > max) {
250         max = array[i];
251       }
252     }
253     return max;
254   }
255 
256   /**
257    * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
258    *
259    * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
260    * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if
261    * {@code value} is greater than {@code max}, {@code max} is returned.
262    *
263    * @param value the {@code int} value to constrain
264    * @param min the lower bound (inclusive) of the range to constrain {@code value} to
265    * @param max the upper bound (inclusive) of the range to constrain {@code value} to
266    * @throws IllegalArgumentException if {@code min > max}
267    * @since 21.0
268    */
269   @Beta
270   public static int constrainToRange(int value, int min, int max) {
271     checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
272     return Math.min(Math.max(value, min), max);
273   }
274 
275   /**
276    * Returns the values from each provided array combined into a single array. For example,
277    * {@code concat(new int[] {a, b}, new int[] {}, new int[] {c}} returns the array {@code {a, b,
278    * 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
300    * {@code 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
304    * {@link 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
316    * {@code 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
366    * {@link Integer#decode} and {@link Integer#toString()}. The returned converter throws
367    * {@link 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   @Beta
376   public static Converter<String, Integer> stringConverter() {
377     return IntConverter.INSTANCE;
378   }
379 
380   /**
381    * Returns an array containing the same values as {@code array}, but guaranteed to be of a
382    * specified minimum length. If {@code array} already has a length of at least {@code minLength},
383    * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
384    * returned, containing the values of {@code array}, and zeroes in the remaining places.
385    *
386    * @param array the source array
387    * @param minLength the minimum length the returned array must guarantee
388    * @param padding an extra amount to "grow" the array by if growth is necessary
389    * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
390    * @return an array containing the values of {@code array}, with guaranteed minimum length
391    *     {@code minLength}
392    */
393   public static int[] ensureCapacity(int[] array, int minLength, int padding) {
394     checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
395     checkArgument(padding >= 0, "Invalid padding: %s", padding);
396     return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
397   }
398 
399   /**
400    * Returns a string containing the supplied {@code int} values separated by {@code separator}. For
401    * example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
402    *
403    * @param separator the text that should appear between consecutive values in the resulting string
404    *     (but not at the start or end)
405    * @param array an array of {@code int} values, possibly empty
406    */
407   public static String join(String separator, int... array) {
408     checkNotNull(separator);
409     if (array.length == 0) {
410       return "";
411     }
412 
413     // For pre-sizing a builder, just get the right order of magnitude
414     StringBuilder builder = new StringBuilder(array.length * 5);
415     builder.append(array[0]);
416     for (int i = 1; i < array.length; i++) {
417       builder.append(separator).append(array[i]);
418     }
419     return builder.toString();
420   }
421 
422   /**
423    * Returns a comparator that compares two {@code int} arrays <a
424    * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
425    * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
426    * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
427    * example, {@code [] < [1] < [1, 2] < [2]}.
428    *
429    * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
430    * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
431    *
432    * @since 2.0
433    */
434   public static Comparator<int[]> lexicographicalComparator() {
435     return LexicographicalComparator.INSTANCE;
436   }
437 
438   private enum LexicographicalComparator implements Comparator<int[]> {
439     INSTANCE;
440 
441     @Override
442     public int compare(int[] left, int[] right) {
443       int minLength = Math.min(left.length, right.length);
444       for (int i = 0; i < minLength; i++) {
445         int result = Ints.compare(left[i], right[i]);
446         if (result != 0) {
447           return result;
448         }
449       }
450       return left.length - right.length;
451     }
452 
453     @Override
454     public String toString() {
455       return "Ints.lexicographicalComparator()";
456     }
457   }
458 
459   /**
460    * Sorts the elements of {@code array} in descending order.
461    *
462    * @since 23.1
463    */
464   public static void sortDescending(int[] array) {
465     checkNotNull(array);
466     sortDescending(array, 0, array.length);
467   }
468 
469   /**
470    * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
471    * exclusive in descending order.
472    *
473    * @since 23.1
474    */
475   public static void sortDescending(int[] array, int fromIndex, int toIndex) {
476     checkNotNull(array);
477     checkPositionIndexes(fromIndex, toIndex, array.length);
478     Arrays.sort(array, fromIndex, toIndex);
479     reverse(array, fromIndex, toIndex);
480   }
481 
482   /**
483    * Reverses the elements of {@code array}. This is equivalent to {@code
484    * Collections.reverse(Ints.asList(array))}, but is likely to be more efficient.
485    *
486    * @since 23.1
487    */
488   public static void reverse(int[] array) {
489     checkNotNull(array);
490     reverse(array, 0, array.length);
491   }
492 
493   /**
494    * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
495    * exclusive. This is equivalent to {@code
496    * Collections.reverse(Ints.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
497    * efficient.
498    *
499    * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
500    *     {@code toIndex > fromIndex}
501    * @since 23.1
502    */
503   public static void reverse(int[] array, int fromIndex, int toIndex) {
504     checkNotNull(array);
505     checkPositionIndexes(fromIndex, toIndex, array.length);
506     for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
507       int tmp = array[i];
508       array[i] = array[j];
509       array[j] = tmp;
510     }
511   }
512 
513   /**
514    * Returns an array containing each value of {@code collection}, converted to a {@code int} value
515    * in the manner of {@link Number#intValue}.
516    *
517    * <p>Elements are copied from the argument collection as if by {@code
518    * collection.toArray()}. Calling this method is as thread-safe as calling that method.
519    *
520    * @param collection a collection of {@code Number} instances
521    * @return an array containing the same values as {@code collection}, in the same order, converted
522    *     to primitives
523    * @throws NullPointerException if {@code collection} or any of its elements is null
524    * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0)
525    */
526   public static int[] toArray(Collection<? extends Number> collection) {
527     if (collection instanceof IntArrayAsList) {
528       return ((IntArrayAsList) collection).toIntArray();
529     }
530 
531     Object[] boxedArray = collection.toArray();
532     int len = boxedArray.length;
533     int[] array = new int[len];
534     for (int i = 0; i < len; i++) {
535       // checkNotNull for GWT (do not optimize)
536       array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
537     }
538     return array;
539   }
540 
541   /**
542    * Returns a fixed-size list backed by the specified array, similar to {@link
543    * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
544    * set a value to {@code null} will result in a {@link NullPointerException}.
545    *
546    * <p>The returned list maintains the values, but not the identities, of {@code Integer} objects
547    * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
548    * the returned list is unspecified.
549    *
550    * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableIntArray}
551    * instead, which has an {@link ImmutableIntArray#asList asList} view.
552    *
553    * @param backingArray the array to back the list
554    * @return a list view of the array
555    */
556   public static List<Integer> asList(int... backingArray) {
557     if (backingArray.length == 0) {
558       return Collections.emptyList();
559     }
560     return new IntArrayAsList(backingArray);
561   }
562 
563   @GwtCompatible
564   private static class IntArrayAsList extends AbstractList<Integer>
565       implements RandomAccess, Serializable {
566     final int[] array;
567     final int start;
568     final int end;
569 
570     IntArrayAsList(int[] array) {
571       this(array, 0, array.length);
572     }
573 
574     IntArrayAsList(int[] array, int start, int end) {
575       this.array = array;
576       this.start = start;
577       this.end = end;
578     }
579 
580     @Override
581     public int size() {
582       return end - start;
583     }
584 
585     @Override
586     public boolean isEmpty() {
587       return false;
588     }
589 
590     @Override
591     public Integer get(int index) {
592       checkElementIndex(index, size());
593       return array[start + index];
594     }
595 
596     @Override
597     public Spliterator.OfInt spliterator() {
598       return Spliterators.spliterator(array, start, end, 0);
599     }
600 
601     @Override
602     public boolean contains(Object target) {
603       // Overridden to prevent a ton of boxing
604       return (target instanceof Integer) && Ints.indexOf(array, (Integer) target, start, end) != -1;
605     }
606 
607     @Override
608     public int indexOf(Object target) {
609       // Overridden to prevent a ton of boxing
610       if (target instanceof Integer) {
611         int i = Ints.indexOf(array, (Integer) target, start, end);
612         if (i >= 0) {
613           return i - start;
614         }
615       }
616       return -1;
617     }
618 
619     @Override
620     public int lastIndexOf(Object target) {
621       // Overridden to prevent a ton of boxing
622       if (target instanceof Integer) {
623         int i = Ints.lastIndexOf(array, (Integer) target, start, end);
624         if (i >= 0) {
625           return i - start;
626         }
627       }
628       return -1;
629     }
630 
631     @Override
632     public Integer set(int index, Integer element) {
633       checkElementIndex(index, size());
634       int oldValue = array[start + index];
635       // checkNotNull for GWT (do not optimize)
636       array[start + index] = checkNotNull(element);
637       return oldValue;
638     }
639 
640     @Override
641     public List<Integer> subList(int fromIndex, int toIndex) {
642       int size = size();
643       checkPositionIndexes(fromIndex, toIndex, size);
644       if (fromIndex == toIndex) {
645         return Collections.emptyList();
646       }
647       return new IntArrayAsList(array, start + fromIndex, start + toIndex);
648     }
649 
650     @Override
651     public boolean equals(@Nullable Object object) {
652       if (object == this) {
653         return true;
654       }
655       if (object instanceof IntArrayAsList) {
656         IntArrayAsList that = (IntArrayAsList) object;
657         int size = size();
658         if (that.size() != size) {
659           return false;
660         }
661         for (int i = 0; i < size; i++) {
662           if (array[start + i] != that.array[that.start + i]) {
663             return false;
664           }
665         }
666         return true;
667       }
668       return super.equals(object);
669     }
670 
671     @Override
672     public int hashCode() {
673       int result = 1;
674       for (int i = start; i < end; i++) {
675         result = 31 * result + Ints.hashCode(array[i]);
676       }
677       return result;
678     }
679 
680     @Override
681     public String toString() {
682       StringBuilder builder = new StringBuilder(size() * 5);
683       builder.append('[').append(array[start]);
684       for (int i = start + 1; i < end; i++) {
685         builder.append(", ").append(array[i]);
686       }
687       return builder.append(']').toString();
688     }
689 
690     int[] toIntArray() {
691       return Arrays.copyOfRange(array, start, end);
692     }
693 
694     private static final long serialVersionUID = 0;
695   }
696 
697   /**
698    * Parses the specified string as a signed decimal integer value. The ASCII character {@code '-'}
699    * (<code>'&#92;u002D'</code>) is recognized as the minus sign.
700    *
701    * <p>Unlike {@link Integer#parseInt(String)}, this method returns {@code null} instead of
702    * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
703    * and returns {@code null} if non-ASCII digits are present in the string.
704    *
705    * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
706    * the change to {@link Integer#parseInt(String)} for that version.
707    *
708    * @param string the string representation of an integer value
709    * @return the integer value represented by {@code string}, or {@code null} if {@code string} has
710    *     a length of zero or cannot be parsed as an integer value
711    * @since 11.0
712    */
713   @Beta
714   @Nullable
715   @CheckForNull
716   public static Integer tryParse(String string) {
717     return tryParse(string, 10);
718   }
719 
720   /**
721    * Parses the specified string as a signed integer value using the specified radix. The ASCII
722    * character {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
723    *
724    * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns {@code null} instead of
725    * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
726    * and returns {@code null} if non-ASCII digits are present in the string.
727    *
728    * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
729    * the change to {@link Integer#parseInt(String, int)} for that version.
730    *
731    * @param string the string representation of an integer value
732    * @param radix the radix to use when parsing
733    * @return the integer value represented by {@code string} using {@code radix}, or {@code null} if
734    *     {@code string} has a length of zero or cannot be parsed as an integer value
735    * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or
736    *     {@code radix > Character.MAX_RADIX}
737    * @since 19.0
738    */
739   @Beta
740   @Nullable
741   @CheckForNull
742   public static Integer tryParse(String string, int radix) {
743     Long result = Longs.tryParse(string, radix);
744     if (result == null || result.longValue() != result.intValue()) {
745       return null;
746     } else {
747       return result.intValue();
748     }
749   }
750 }