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.annotations.GwtIncompatible;
25 import com.google.common.base.Converter;
26 import java.io.Serializable;
27 import java.util.AbstractList;
28 import java.util.Arrays;
29 import java.util.Collection;
30 import java.util.Collections;
31 import java.util.Comparator;
32 import java.util.List;
33 import java.util.RandomAccess;
34 import java.util.Spliterator;
35 import java.util.Spliterators;
36 import javax.annotation.CheckForNull;
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 <a
43 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
44 *
45 * @author Kevin Bourrillion
46 * @since 1.0
47 */
48 @GwtCompatible(emulated = true)
49 @ElementTypesAreNonnullByDefault
50 public final class Ints extends IntsMethodsForWeb {
51 private Ints() {}
52
53 /**
54 * The number of bytes required to represent a primitive {@code int} value.
55 *
56 * <p><b>Java 8 users:</b> use {@link Integer#BYTES} instead.
57 */
58 public static final int BYTES = Integer.SIZE / Byte.SIZE;
59
60 /**
61 * The largest power of two that can be represented as an {@code int}.
62 *
63 * @since 10.0
64 */
65 public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
66
67 /**
68 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Integer)
69 * value).hashCode()}.
70 *
71 * <p><b>Java 8 users:</b> use {@link Integer#hashCode(int)} instead.
72 *
73 * @param value a primitive {@code int} value
74 * @return a hash code for the value
75 */
76 public static int hashCode(int value) {
77 return value;
78 }
79
80 /**
81 * Returns the {@code int} value that is equal to {@code value}, if possible.
82 *
83 * @param value any value in the range of the {@code int} type
84 * @return the {@code int} value that equals {@code value}
85 * @throws IllegalArgumentException if {@code value} is greater than {@link Integer#MAX_VALUE} or
86 * less than {@link Integer#MIN_VALUE}
87 */
88 public static int checkedCast(long value) {
89 int result = (int) value;
90 checkArgument(result == value, "Out of range: %s", value);
91 return result;
92 }
93
94 /**
95 * Returns the {@code int} nearest in value to {@code value}.
96 *
97 * @param value any {@code long} value
98 * @return the same value cast to {@code int} if it is in the range of the {@code int} type,
99 * {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too
100 * small
101 */
102 public static int saturatedCast(long value) {
103 if (value > Integer.MAX_VALUE) {
104 return Integer.MAX_VALUE;
105 }
106 if (value < Integer.MIN_VALUE) {
107 return Integer.MIN_VALUE;
108 }
109 return (int) value;
110 }
111
112 /**
113 * Compares the two specified {@code int} values. The sign of the value returned is the same as
114 * that of {@code ((Integer) a).compareTo(b)}.
115 *
116 * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
117 * equivalent {@link Integer#compare} method instead.
118 *
119 * @param a the first {@code int} to compare
120 * @param b the second {@code int} to compare
121 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
122 * greater than {@code b}; or zero if they are equal
123 */
124 public static int compare(int a, int b) {
125 return (a < b) ? -1 : ((a > b) ? 1 : 0);
126 }
127
128 /**
129 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
130 *
131 * @param array an array of {@code int} values, possibly empty
132 * @param target a primitive {@code int} value
133 * @return {@code true} if {@code array[i] == target} for some value of {@code 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 target} within
168 * {@code array}, or {@code -1} if there is no such occurrence.
169 *
170 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
171 * i, i + target.length)} contains exactly the same elements as {@code target}.
172 *
173 * @param array the array to search for the sequence {@code target}
174 * @param target the array to search for as a sub-sequence of {@code array}
175 */
176 public static int indexOf(int[] array, int[] target) {
177 checkNotNull(array, "array");
178 checkNotNull(target, "target");
179 if (target.length == 0) {
180 return 0;
181 }
182
183 outer:
184 for (int i = 0; i < array.length - target.length + 1; i++) {
185 for (int j = 0; j < target.length; j++) {
186 if (array[i + j] != target[j]) {
187 continue outer;
188 }
189 }
190 return i;
191 }
192 return -1;
193 }
194
195 /**
196 * Returns the index of the last appearance of the value {@code target} in {@code array}.
197 *
198 * @param array an array of {@code int} values, possibly empty
199 * @param target a primitive {@code int} value
200 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
201 * such index exists.
202 */
203 public static int lastIndexOf(int[] array, int target) {
204 return lastIndexOf(array, target, 0, array.length);
205 }
206
207 // TODO(kevinb): consider making this public
208 private static int lastIndexOf(int[] array, int target, int start, int end) {
209 for (int i = end - 1; i >= start; i--) {
210 if (array[i] == target) {
211 return i;
212 }
213 }
214 return -1;
215 }
216
217 /**
218 * Returns the least value present in {@code array}.
219 *
220 * @param array a <i>nonempty</i> array of {@code int} values
221 * @return the value present in {@code array} that is less than or equal to every other value in
222 * the array
223 * @throws IllegalArgumentException if {@code array} is empty
224 */
225 @GwtIncompatible(
226 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
227 public static int min(int... array) {
228 checkArgument(array.length > 0);
229 int min = array[0];
230 for (int i = 1; i < array.length; i++) {
231 if (array[i] < min) {
232 min = array[i];
233 }
234 }
235 return min;
236 }
237
238 /**
239 * Returns the greatest value present in {@code array}.
240 *
241 * @param array a <i>nonempty</i> array of {@code int} values
242 * @return the value present in {@code array} that is greater than or equal to every other value
243 * in the array
244 * @throws IllegalArgumentException if {@code array} is empty
245 */
246 @GwtIncompatible(
247 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
248 public static int max(int... array) {
249 checkArgument(array.length > 0);
250 int max = array[0];
251 for (int i = 1; i < array.length; i++) {
252 if (array[i] > max) {
253 max = array[i];
254 }
255 }
256 return max;
257 }
258
259 /**
260 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
261 *
262 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
263 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
264 * value} is greater than {@code max}, {@code max} is returned.
265 *
266 * @param value the {@code int} value to constrain
267 * @param min the lower bound (inclusive) of the range to constrain {@code value} to
268 * @param max the upper bound (inclusive) of the range to constrain {@code value} to
269 * @throws IllegalArgumentException if {@code min > max}
270 * @since 21.0
271 */
272 @Beta
273 public static int constrainToRange(int value, int min, int max) {
274 checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
275 return Math.min(Math.max(value, min), max);
276 }
277
278 /**
279 * Returns the values from each provided array combined into a single array. For example, {@code
280 * concat(new int[] {a, b}, new int[] {}, new int[] {c}} returns the array {@code {a, b, c}}.
281 *
282 * @param arrays zero or more {@code int} arrays
283 * @return a single array containing all the values from the source arrays, in order
284 */
285 public static int[] concat(int[]... arrays) {
286 int length = 0;
287 for (int[] array : arrays) {
288 length += array.length;
289 }
290 int[] result = new int[length];
291 int pos = 0;
292 for (int[] array : arrays) {
293 System.arraycopy(array, 0, result, pos, array.length);
294 pos += array.length;
295 }
296 return result;
297 }
298
299 /**
300 * Returns a big-endian representation of {@code value} in a 4-element byte array; equivalent to
301 * {@code ByteBuffer.allocate(4).putInt(value).array()}. For example, the input value {@code
302 * 0x12131415} would yield the byte array {@code {0x12, 0x13, 0x14, 0x15}}.
303 *
304 * <p>If you need to convert and concatenate several values (possibly even of different types),
305 * use a shared {@link java.nio.ByteBuffer} instance, or use {@link
306 * com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
307 */
308 public static byte[] toByteArray(int value) {
309 return new byte[] {
310 (byte) (value >> 24), (byte) (value >> 16), (byte) (value >> 8), (byte) value
311 };
312 }
313
314 /**
315 * Returns the {@code int} value whose big-endian representation is stored in the first 4 bytes of
316 * {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getInt()}. For example, the input
317 * byte array {@code {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
318 * 0x12131415}.
319 *
320 * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
321 * flexibility at little cost in readability.
322 *
323 * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
324 */
325 public static int fromByteArray(byte[] bytes) {
326 checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
327 return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
328 }
329
330 /**
331 * Returns the {@code int} value whose byte representation is the given 4 bytes, in big-endian
332 * order; equivalent to {@code Ints.fromByteArray(new byte[] {b1, b2, b3, b4})}.
333 *
334 * @since 7.0
335 */
336 public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
337 return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
338 }
339
340 private static final class IntConverter extends Converter<String, Integer>
341 implements Serializable {
342 static final IntConverter INSTANCE = new IntConverter();
343
344 @Override
345 protected Integer doForward(String value) {
346 return Integer.decode(value);
347 }
348
349 @Override
350 protected String doBackward(Integer value) {
351 return value.toString();
352 }
353
354 @Override
355 public String toString() {
356 return "Ints.stringConverter()";
357 }
358
359 private Object readResolve() {
360 return INSTANCE;
361 }
362
363 private static final long serialVersionUID = 1;
364 }
365
366 /**
367 * Returns a serializable converter object that converts between strings and integers using {@link
368 * Integer#decode} and {@link Integer#toString()}. The returned converter throws {@link
369 * NumberFormatException} if the input string is invalid.
370 *
371 * <p><b>Warning:</b> please see {@link Integer#decode} to understand exactly how strings are
372 * parsed. For example, the string {@code "0123"} is treated as <i>octal</i> and converted to the
373 * value {@code 83}.
374 *
375 * @since 16.0
376 */
377 @Beta
378 public static Converter<String, Integer> stringConverter() {
379 return IntConverter.INSTANCE;
380 }
381
382 /**
383 * Returns an array containing the same values as {@code array}, but guaranteed to be of a
384 * specified minimum length. If {@code array} already has a length of at least {@code minLength},
385 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
386 * returned, containing the values of {@code array}, and zeroes in the remaining places.
387 *
388 * @param array the source array
389 * @param minLength the minimum length the returned array must guarantee
390 * @param padding an extra amount to "grow" the array by if growth is necessary
391 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
392 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
393 * minLength}
394 */
395 public static int[] ensureCapacity(int[] array, int minLength, int padding) {
396 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
397 checkArgument(padding >= 0, "Invalid padding: %s", padding);
398 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
399 }
400
401 /**
402 * Returns a string containing the supplied {@code int} values separated by {@code separator}. For
403 * example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
404 *
405 * @param separator the text that should appear between consecutive values in the resulting string
406 * (but not at the start or end)
407 * @param array an array of {@code int} values, possibly empty
408 */
409 public static String join(String separator, int... array) {
410 checkNotNull(separator);
411 if (array.length == 0) {
412 return "";
413 }
414
415 // For pre-sizing a builder, just get the right order of magnitude
416 StringBuilder builder = new StringBuilder(array.length * 5);
417 builder.append(array[0]);
418 for (int i = 1; i < array.length; i++) {
419 builder.append(separator).append(array[i]);
420 }
421 return builder.toString();
422 }
423
424 /**
425 * Returns a comparator that compares two {@code int} arrays <a
426 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
427 * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
428 * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
429 * example, {@code [] < [1] < [1, 2] < [2]}.
430 *
431 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
432 * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
433 *
434 * @since 2.0
435 */
436 public static Comparator<int[]> lexicographicalComparator() {
437 return LexicographicalComparator.INSTANCE;
438 }
439
440 private enum LexicographicalComparator implements Comparator<int[]> {
441 INSTANCE;
442
443 @Override
444 public int compare(int[] left, int[] right) {
445 int minLength = Math.min(left.length, right.length);
446 for (int i = 0; i < minLength; i++) {
447 int result = Ints.compare(left[i], right[i]);
448 if (result != 0) {
449 return result;
450 }
451 }
452 return left.length - right.length;
453 }
454
455 @Override
456 public String toString() {
457 return "Ints.lexicographicalComparator()";
458 }
459 }
460
461 /**
462 * Sorts the elements of {@code array} in descending order.
463 *
464 * @since 23.1
465 */
466 public static void sortDescending(int[] array) {
467 checkNotNull(array);
468 sortDescending(array, 0, array.length);
469 }
470
471 /**
472 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
473 * exclusive in descending order.
474 *
475 * @since 23.1
476 */
477 public static void sortDescending(int[] array, int fromIndex, int toIndex) {
478 checkNotNull(array);
479 checkPositionIndexes(fromIndex, toIndex, array.length);
480 Arrays.sort(array, fromIndex, toIndex);
481 reverse(array, fromIndex, toIndex);
482 }
483
484 /**
485 * Reverses the elements of {@code array}. This is equivalent to {@code
486 * Collections.reverse(Ints.asList(array))}, but is likely to be more efficient.
487 *
488 * @since 23.1
489 */
490 public static void reverse(int[] array) {
491 checkNotNull(array);
492 reverse(array, 0, array.length);
493 }
494
495 /**
496 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
497 * exclusive. This is equivalent to {@code
498 * Collections.reverse(Ints.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
499 * efficient.
500 *
501 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
502 * {@code toIndex > fromIndex}
503 * @since 23.1
504 */
505 public static void reverse(int[] array, int fromIndex, int toIndex) {
506 checkNotNull(array);
507 checkPositionIndexes(fromIndex, toIndex, array.length);
508 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
509 int tmp = array[i];
510 array[i] = array[j];
511 array[j] = tmp;
512 }
513 }
514
515 /**
516 * Returns an array containing each value of {@code collection}, converted to a {@code int} value
517 * in the manner of {@link Number#intValue}.
518 *
519 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
520 * Calling this method is as thread-safe as calling that method.
521 *
522 * @param collection a collection of {@code Number} instances
523 * @return an array containing the same values as {@code collection}, in the same order, converted
524 * to primitives
525 * @throws NullPointerException if {@code collection} or any of its elements is null
526 * @since 1.0 (parameter was {@code Collection<Integer>} before 12.0)
527 */
528 public static int[] toArray(Collection<? extends Number> collection) {
529 if (collection instanceof IntArrayAsList) {
530 return ((IntArrayAsList) collection).toIntArray();
531 }
532
533 Object[] boxedArray = collection.toArray();
534 int len = boxedArray.length;
535 int[] array = new int[len];
536 for (int i = 0; i < len; i++) {
537 // checkNotNull for GWT (do not optimize)
538 array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
539 }
540 return array;
541 }
542
543 /**
544 * Returns a fixed-size list backed by the specified array, similar to {@link
545 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
546 * set a value to {@code null} will result in a {@link NullPointerException}.
547 *
548 * <p>The returned list maintains the values, but not the identities, of {@code Integer} objects
549 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
550 * the returned list is unspecified.
551 *
552 * <p><b>Note:</b> when possible, you should represent your data as an {@link ImmutableIntArray}
553 * instead, which has an {@link ImmutableIntArray#asList asList} view.
554 *
555 * @param backingArray the array to back the list
556 * @return a list view of the array
557 */
558 public static List<Integer> asList(int... backingArray) {
559 if (backingArray.length == 0) {
560 return Collections.emptyList();
561 }
562 return new IntArrayAsList(backingArray);
563 }
564
565 @GwtCompatible
566 private static class IntArrayAsList extends AbstractList<Integer>
567 implements RandomAccess, Serializable {
568 final int[] array;
569 final int start;
570 final int end;
571
572 IntArrayAsList(int[] array) {
573 this(array, 0, array.length);
574 }
575
576 IntArrayAsList(int[] array, int start, int end) {
577 this.array = array;
578 this.start = start;
579 this.end = end;
580 }
581
582 @Override
583 public int size() {
584 return end - start;
585 }
586
587 @Override
588 public boolean isEmpty() {
589 return false;
590 }
591
592 @Override
593 public Integer get(int index) {
594 checkElementIndex(index, size());
595 return array[start + index];
596 }
597
598 @Override
599 public Spliterator.OfInt spliterator() {
600 return Spliterators.spliterator(array, start, end, 0);
601 }
602
603 @Override
604 public boolean contains(@CheckForNull Object target) {
605 // Overridden to prevent a ton of boxing
606 return (target instanceof Integer) && Ints.indexOf(array, (Integer) target, start, end) != -1;
607 }
608
609 @Override
610 public int indexOf(@CheckForNull Object target) {
611 // Overridden to prevent a ton of boxing
612 if (target instanceof Integer) {
613 int i = Ints.indexOf(array, (Integer) target, start, end);
614 if (i >= 0) {
615 return i - start;
616 }
617 }
618 return -1;
619 }
620
621 @Override
622 public int lastIndexOf(@CheckForNull Object target) {
623 // Overridden to prevent a ton of boxing
624 if (target instanceof Integer) {
625 int i = Ints.lastIndexOf(array, (Integer) target, start, end);
626 if (i >= 0) {
627 return i - start;
628 }
629 }
630 return -1;
631 }
632
633 @Override
634 public Integer set(int index, Integer element) {
635 checkElementIndex(index, size());
636 int oldValue = array[start + index];
637 // checkNotNull for GWT (do not optimize)
638 array[start + index] = checkNotNull(element);
639 return oldValue;
640 }
641
642 @Override
643 public List<Integer> subList(int fromIndex, int toIndex) {
644 int size = size();
645 checkPositionIndexes(fromIndex, toIndex, size);
646 if (fromIndex == toIndex) {
647 return Collections.emptyList();
648 }
649 return new IntArrayAsList(array, start + fromIndex, start + toIndex);
650 }
651
652 @Override
653 public boolean equals(@CheckForNull Object object) {
654 if (object == this) {
655 return true;
656 }
657 if (object instanceof IntArrayAsList) {
658 IntArrayAsList that = (IntArrayAsList) object;
659 int size = size();
660 if (that.size() != size) {
661 return false;
662 }
663 for (int i = 0; i < size; i++) {
664 if (array[start + i] != that.array[that.start + i]) {
665 return false;
666 }
667 }
668 return true;
669 }
670 return super.equals(object);
671 }
672
673 @Override
674 public int hashCode() {
675 int result = 1;
676 for (int i = start; i < end; i++) {
677 result = 31 * result + Ints.hashCode(array[i]);
678 }
679 return result;
680 }
681
682 @Override
683 public String toString() {
684 StringBuilder builder = new StringBuilder(size() * 5);
685 builder.append('[').append(array[start]);
686 for (int i = start + 1; i < end; i++) {
687 builder.append(", ").append(array[i]);
688 }
689 return builder.append(']').toString();
690 }
691
692 int[] toIntArray() {
693 return Arrays.copyOfRange(array, start, end);
694 }
695
696 private static final long serialVersionUID = 0;
697 }
698
699 /**
700 * Parses the specified string as a signed decimal integer value. The ASCII character {@code '-'}
701 * (<code>'\u002D'</code>) is recognized as the minus sign.
702 *
703 * <p>Unlike {@link Integer#parseInt(String)}, this method returns {@code null} instead of
704 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
705 * and returns {@code null} if non-ASCII digits are present in the string.
706 *
707 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
708 * the change to {@link Integer#parseInt(String)} for that version.
709 *
710 * @param string the string representation of an integer value
711 * @return the integer value represented by {@code string}, or {@code null} if {@code string} has
712 * a length of zero or cannot be parsed as an integer value
713 * @throws NullPointerException if {@code string} is {@code null}
714 * @since 11.0
715 */
716 @Beta
717 @CheckForNull
718 public static Integer tryParse(String string) {
719 return tryParse(string, 10);
720 }
721
722 /**
723 * Parses the specified string as a signed integer value using the specified radix. The ASCII
724 * character {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign.
725 *
726 * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns {@code null} instead of
727 * throwing an exception if parsing fails. Additionally, this method only accepts ASCII digits,
728 * and returns {@code null} if non-ASCII digits are present in the string.
729 *
730 * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even under JDK 7, despite
731 * the change to {@link Integer#parseInt(String, int)} for that version.
732 *
733 * @param string the string representation of an integer value
734 * @param radix the radix to use when parsing
735 * @return the integer value represented by {@code string} using {@code radix}, or {@code null} if
736 * {@code string} has a length of zero or cannot be parsed as an integer value
737 * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or {@code radix >
738 * Character.MAX_RADIX}
739 * @throws NullPointerException if {@code string} is {@code null}
740 * @since 19.0
741 */
742 @Beta
743 @CheckForNull
744 public static Integer tryParse(String string, int radix) {
745 Long result = Longs.tryParse(string, radix);
746 if (result == null || result.longValue() != result.intValue()) {
747 return null;
748 } else {
749 return result.intValue();
750 }
751 }
752 }