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 import static com.google.common.base.Strings.lenientFormat;
22 import static java.lang.Double.NEGATIVE_INFINITY;
23 import static java.lang.Double.POSITIVE_INFINITY;
24
25 import com.google.common.annotations.Beta;
26 import com.google.common.annotations.GwtCompatible;
27 import com.google.common.annotations.GwtIncompatible;
28 import com.google.common.base.Converter;
29 import java.io.Serializable;
30 import java.util.AbstractList;
31 import java.util.Arrays;
32 import java.util.Collection;
33 import java.util.Collections;
34 import java.util.Comparator;
35 import java.util.List;
36 import java.util.RandomAccess;
37 import java.util.Spliterator;
38 import java.util.Spliterators;
39 import javax.annotation.CheckForNull;
40
41 /**
42 * Static utility methods pertaining to {@code double} primitives, that are not already found in
43 * either {@link Double} or {@link Arrays}.
44 *
45 * <p>See the Guava User Guide article on <a
46 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
47 *
48 * @author Kevin Bourrillion
49 * @since 1.0
50 */
51 @GwtCompatible(emulated = true)
52 @ElementTypesAreNonnullByDefault
53 public final class Doubles extends DoublesMethodsForWeb {
54 private Doubles() {}
55
56 /**
57 * The number of bytes required to represent a primitive {@code double} value.
58 *
59 * <p><b>Java 8 users:</b> use {@link Double#BYTES} instead.
60 *
61 * @since 10.0
62 */
63 public static final int BYTES = Double.SIZE / Byte.SIZE;
64
65 /**
66 * Returns a hash code for {@code value}; equal to the result of invoking {@code ((Double)
67 * value).hashCode()}.
68 *
69 * <p><b>Java 8 users:</b> use {@link Double#hashCode(double)} instead.
70 *
71 * @param value a primitive {@code double} value
72 * @return a hash code for the value
73 */
74 public static int hashCode(double value) {
75 return ((Double) value).hashCode();
76 // TODO(kevinb): do it this way when we can (GWT problem):
77 // long bits = Double.doubleToLongBits(value);
78 // return (int) (bits ^ (bits >>> 32));
79 }
80
81 /**
82 * Compares the two specified {@code double} values. The sign of the value returned is the same as
83 * that of <code>((Double) a).{@linkplain Double#compareTo compareTo}(b)</code>. As with that
84 * method, {@code NaN} is treated as greater than all other values, and {@code 0.0 > -0.0}.
85 *
86 * <p><b>Note:</b> this method simply delegates to the JDK method {@link Double#compare}. It is
87 * provided for consistency with the other primitive types, whose compare methods were not added
88 * to the JDK until JDK 7.
89 *
90 * @param a the first {@code double} to compare
91 * @param b the second {@code double} to compare
92 * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
93 * greater than {@code b}; or zero if they are equal
94 */
95 public static int compare(double a, double b) {
96 return Double.compare(a, b);
97 }
98
99 /**
100 * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not
101 * necessarily implemented as, {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
102 *
103 * <p><b>Java 8 users:</b> use {@link Double#isFinite(double)} instead.
104 *
105 * @since 10.0
106 */
107 public static boolean isFinite(double value) {
108 return NEGATIVE_INFINITY < value && value < POSITIVE_INFINITY;
109 }
110
111 /**
112 * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}. Note
113 * that this always returns {@code false} when {@code target} is {@code NaN}.
114 *
115 * @param array an array of {@code double} values, possibly empty
116 * @param target a primitive {@code double} value
117 * @return {@code true} if {@code array[i] == target} for some value of {@code i}
118 */
119 public static boolean contains(double[] array, double target) {
120 for (double value : array) {
121 if (value == target) {
122 return true;
123 }
124 }
125 return false;
126 }
127
128 /**
129 * Returns the index of the first appearance of the value {@code target} in {@code array}. Note
130 * that this always returns {@code -1} when {@code target} is {@code NaN}.
131 *
132 * @param array an array of {@code double} values, possibly empty
133 * @param target a primitive {@code double} value
134 * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
135 * such index exists.
136 */
137 public static int indexOf(double[] array, double target) {
138 return indexOf(array, target, 0, array.length);
139 }
140
141 // TODO(kevinb): consider making this public
142 private static int indexOf(double[] array, double target, int start, int end) {
143 for (int i = start; i < end; i++) {
144 if (array[i] == target) {
145 return i;
146 }
147 }
148 return -1;
149 }
150
151 /**
152 * Returns the start position of the first occurrence of the specified {@code target} within
153 * {@code array}, or {@code -1} if there is no such occurrence.
154 *
155 * <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
156 * i, i + target.length)} contains exactly the same elements as {@code target}.
157 *
158 * <p>Note that this always returns {@code -1} when {@code target} contains {@code NaN}.
159 *
160 * @param array the array to search for the sequence {@code target}
161 * @param target the array to search for as a sub-sequence of {@code array}
162 */
163 public static int indexOf(double[] array, double[] target) {
164 checkNotNull(array, "array");
165 checkNotNull(target, "target");
166 if (target.length == 0) {
167 return 0;
168 }
169
170 outer:
171 for (int i = 0; i < array.length - target.length + 1; i++) {
172 for (int j = 0; j < target.length; j++) {
173 if (array[i + j] != target[j]) {
174 continue outer;
175 }
176 }
177 return i;
178 }
179 return -1;
180 }
181
182 /**
183 * Returns the index of the last appearance of the value {@code target} in {@code array}. Note
184 * that this always returns {@code -1} when {@code target} is {@code NaN}.
185 *
186 * @param array an array of {@code double} values, possibly empty
187 * @param target a primitive {@code double} value
188 * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
189 * such index exists.
190 */
191 public static int lastIndexOf(double[] array, double target) {
192 return lastIndexOf(array, target, 0, array.length);
193 }
194
195 // TODO(kevinb): consider making this public
196 private static int lastIndexOf(double[] array, double target, int start, int end) {
197 for (int i = end - 1; i >= start; i--) {
198 if (array[i] == target) {
199 return i;
200 }
201 }
202 return -1;
203 }
204
205 /**
206 * Returns the least value present in {@code array}, using the same rules of comparison as {@link
207 * Math#min(double, double)}.
208 *
209 * @param array a <i>nonempty</i> array of {@code double} values
210 * @return the value present in {@code array} that is less than or equal to every other value in
211 * the array
212 * @throws IllegalArgumentException if {@code array} is empty
213 */
214 @GwtIncompatible(
215 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
216 public static double min(double... array) {
217 checkArgument(array.length > 0);
218 double min = array[0];
219 for (int i = 1; i < array.length; i++) {
220 min = Math.min(min, array[i]);
221 }
222 return min;
223 }
224
225 /**
226 * Returns the greatest value present in {@code array}, using the same rules of comparison as
227 * {@link Math#max(double, double)}.
228 *
229 * @param array a <i>nonempty</i> array of {@code double} values
230 * @return the value present in {@code array} that is greater than or equal to every other value
231 * in the array
232 * @throws IllegalArgumentException if {@code array} is empty
233 */
234 @GwtIncompatible(
235 "Available in GWT! Annotation is to avoid conflict with GWT specialization of base class.")
236 public static double max(double... array) {
237 checkArgument(array.length > 0);
238 double max = array[0];
239 for (int i = 1; i < array.length; i++) {
240 max = Math.max(max, array[i]);
241 }
242 return max;
243 }
244
245 /**
246 * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
247 *
248 * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
249 * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
250 * value} is greater than {@code max}, {@code max} is returned.
251 *
252 * @param value the {@code double} value to constrain
253 * @param min the lower bound (inclusive) of the range to constrain {@code value} to
254 * @param max the upper bound (inclusive) of the range to constrain {@code value} to
255 * @throws IllegalArgumentException if {@code min > max}
256 * @since 21.0
257 */
258 @Beta
259 public static double constrainToRange(double value, double min, double max) {
260 // avoid auto-boxing by not using Preconditions.checkArgument(); see Guava issue 3984
261 // Reject NaN by testing for the good case (min <= max) instead of the bad (min > max).
262 if (min <= max) {
263 return Math.min(Math.max(value, min), max);
264 }
265 throw new IllegalArgumentException(
266 lenientFormat("min (%s) must be less than or equal to max (%s)", min, max));
267 }
268
269 /**
270 * Returns the values from each provided array combined into a single array. For example, {@code
271 * concat(new double[] {a, b}, new double[] {}, new double[] {c}} returns the array {@code {a, b,
272 * c}}.
273 *
274 * @param arrays zero or more {@code double} arrays
275 * @return a single array containing all the values from the source arrays, in order
276 */
277 public static double[] concat(double[]... arrays) {
278 int length = 0;
279 for (double[] array : arrays) {
280 length += array.length;
281 }
282 double[] result = new double[length];
283 int pos = 0;
284 for (double[] array : arrays) {
285 System.arraycopy(array, 0, result, pos, array.length);
286 pos += array.length;
287 }
288 return result;
289 }
290
291 private static final class DoubleConverter extends Converter<String, Double>
292 implements Serializable {
293 static final DoubleConverter INSTANCE = new DoubleConverter();
294
295 @Override
296 protected Double doForward(String value) {
297 return Double.valueOf(value);
298 }
299
300 @Override
301 protected String doBackward(Double value) {
302 return value.toString();
303 }
304
305 @Override
306 public String toString() {
307 return "Doubles.stringConverter()";
308 }
309
310 private Object readResolve() {
311 return INSTANCE;
312 }
313
314 private static final long serialVersionUID = 1;
315 }
316
317 /**
318 * Returns a serializable converter object that converts between strings and doubles using {@link
319 * Double#valueOf} and {@link Double#toString()}.
320 *
321 * @since 16.0
322 */
323 @Beta
324 public static Converter<String, Double> stringConverter() {
325 return DoubleConverter.INSTANCE;
326 }
327
328 /**
329 * Returns an array containing the same values as {@code array}, but guaranteed to be of a
330 * specified minimum length. If {@code array} already has a length of at least {@code minLength},
331 * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
332 * returned, containing the values of {@code array}, and zeroes in the remaining places.
333 *
334 * @param array the source array
335 * @param minLength the minimum length the returned array must guarantee
336 * @param padding an extra amount to "grow" the array by if growth is necessary
337 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
338 * @return an array containing the values of {@code array}, with guaranteed minimum length {@code
339 * minLength}
340 */
341 public static double[] ensureCapacity(double[] array, int minLength, int padding) {
342 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
343 checkArgument(padding >= 0, "Invalid padding: %s", padding);
344 return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
345 }
346
347 /**
348 * Returns a string containing the supplied {@code double} values, converted to strings as
349 * specified by {@link Double#toString(double)}, and separated by {@code separator}. For example,
350 * {@code join("-", 1.0, 2.0, 3.0)} returns the string {@code "1.0-2.0-3.0"}.
351 *
352 * <p>Note that {@link Double#toString(double)} formats {@code double} differently in GWT
353 * sometimes. In the previous example, it returns the string {@code "1-2-3"}.
354 *
355 * @param separator the text that should appear between consecutive values in the resulting string
356 * (but not at the start or end)
357 * @param array an array of {@code double} values, possibly empty
358 */
359 public static String join(String separator, double... array) {
360 checkNotNull(separator);
361 if (array.length == 0) {
362 return "";
363 }
364
365 // For pre-sizing a builder, just get the right order of magnitude
366 StringBuilder builder = new StringBuilder(array.length * 12);
367 builder.append(array[0]);
368 for (int i = 1; i < array.length; i++) {
369 builder.append(separator).append(array[i]);
370 }
371 return builder.toString();
372 }
373
374 /**
375 * Returns a comparator that compares two {@code double} arrays <a
376 * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
377 * compares, using {@link #compare(double, double)}), the first pair of values that follow any
378 * common prefix, or when one array is a prefix of the other, treats the shorter array as the
379 * lesser. For example, {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
380 *
381 * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
382 * support only identity equality), but it is consistent with {@link Arrays#equals(double[],
383 * double[])}.
384 *
385 * @since 2.0
386 */
387 public static Comparator<double[]> lexicographicalComparator() {
388 return LexicographicalComparator.INSTANCE;
389 }
390
391 private enum LexicographicalComparator implements Comparator<double[]> {
392 INSTANCE;
393
394 @Override
395 public int compare(double[] left, double[] right) {
396 int minLength = Math.min(left.length, right.length);
397 for (int i = 0; i < minLength; i++) {
398 int result = Double.compare(left[i], right[i]);
399 if (result != 0) {
400 return result;
401 }
402 }
403 return left.length - right.length;
404 }
405
406 @Override
407 public String toString() {
408 return "Doubles.lexicographicalComparator()";
409 }
410 }
411
412 /**
413 * Sorts the elements of {@code array} in descending order.
414 *
415 * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
416 * all NaN values as equal and 0.0 as greater than -0.0.
417 *
418 * @since 23.1
419 */
420 public static void sortDescending(double[] array) {
421 checkNotNull(array);
422 sortDescending(array, 0, array.length);
423 }
424
425 /**
426 * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
427 * exclusive in descending order.
428 *
429 * <p>Note that this method uses the total order imposed by {@link Double#compare}, which treats
430 * all NaN values as equal and 0.0 as greater than -0.0.
431 *
432 * @since 23.1
433 */
434 public static void sortDescending(double[] array, int fromIndex, int toIndex) {
435 checkNotNull(array);
436 checkPositionIndexes(fromIndex, toIndex, array.length);
437 Arrays.sort(array, fromIndex, toIndex);
438 reverse(array, fromIndex, toIndex);
439 }
440
441 /**
442 * Reverses the elements of {@code array}. This is equivalent to {@code
443 * Collections.reverse(Doubles.asList(array))}, but is likely to be more efficient.
444 *
445 * @since 23.1
446 */
447 public static void reverse(double[] array) {
448 checkNotNull(array);
449 reverse(array, 0, array.length);
450 }
451
452 /**
453 * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
454 * exclusive. This is equivalent to {@code
455 * Collections.reverse(Doubles.asList(array).subList(fromIndex, toIndex))}, but is likely to be
456 * more efficient.
457 *
458 * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
459 * {@code toIndex > fromIndex}
460 * @since 23.1
461 */
462 public static void reverse(double[] array, int fromIndex, int toIndex) {
463 checkNotNull(array);
464 checkPositionIndexes(fromIndex, toIndex, array.length);
465 for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
466 double tmp = array[i];
467 array[i] = array[j];
468 array[j] = tmp;
469 }
470 }
471
472 /**
473 * Returns an array containing each value of {@code collection}, converted to a {@code double}
474 * value in the manner of {@link Number#doubleValue}.
475 *
476 * <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
477 * Calling this method is as thread-safe as calling that method.
478 *
479 * @param collection a collection of {@code Number} instances
480 * @return an array containing the same values as {@code collection}, in the same order, converted
481 * to primitives
482 * @throws NullPointerException if {@code collection} or any of its elements is null
483 * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
484 */
485 public static double[] toArray(Collection<? extends Number> collection) {
486 if (collection instanceof DoubleArrayAsList) {
487 return ((DoubleArrayAsList) collection).toDoubleArray();
488 }
489
490 Object[] boxedArray = collection.toArray();
491 int len = boxedArray.length;
492 double[] array = new double[len];
493 for (int i = 0; i < len; i++) {
494 // checkNotNull for GWT (do not optimize)
495 array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
496 }
497 return array;
498 }
499
500 /**
501 * Returns a fixed-size list backed by the specified array, similar to {@link
502 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
503 * set a value to {@code null} will result in a {@link NullPointerException}.
504 *
505 * <p>The returned list maintains the values, but not the identities, of {@code Double} objects
506 * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
507 * the returned list is unspecified.
508 *
509 * <p>The returned list may have unexpected behavior if it contains {@code NaN}, or if {@code NaN}
510 * is used as a parameter to any of its methods.
511 *
512 * <p><b>Note:</b> when possible, you should represent your data as an {@link
513 * ImmutableDoubleArray} instead, which has an {@link ImmutableDoubleArray#asList asList} view.
514 *
515 * @param backingArray the array to back the list
516 * @return a list view of the array
517 */
518 public static List<Double> asList(double... backingArray) {
519 if (backingArray.length == 0) {
520 return Collections.emptyList();
521 }
522 return new DoubleArrayAsList(backingArray);
523 }
524
525 @GwtCompatible
526 private static class DoubleArrayAsList extends AbstractList<Double>
527 implements RandomAccess, Serializable {
528 final double[] array;
529 final int start;
530 final int end;
531
532 DoubleArrayAsList(double[] array) {
533 this(array, 0, array.length);
534 }
535
536 DoubleArrayAsList(double[] array, int start, int end) {
537 this.array = array;
538 this.start = start;
539 this.end = end;
540 }
541
542 @Override
543 public int size() {
544 return end - start;
545 }
546
547 @Override
548 public boolean isEmpty() {
549 return false;
550 }
551
552 @Override
553 public Double get(int index) {
554 checkElementIndex(index, size());
555 return array[start + index];
556 }
557
558 @Override
559 public Spliterator.OfDouble spliterator() {
560 return Spliterators.spliterator(array, start, end, 0);
561 }
562
563 @Override
564 public boolean contains(@CheckForNull Object target) {
565 // Overridden to prevent a ton of boxing
566 return (target instanceof Double)
567 && Doubles.indexOf(array, (Double) target, start, end) != -1;
568 }
569
570 @Override
571 public int indexOf(@CheckForNull Object target) {
572 // Overridden to prevent a ton of boxing
573 if (target instanceof Double) {
574 int i = Doubles.indexOf(array, (Double) target, start, end);
575 if (i >= 0) {
576 return i - start;
577 }
578 }
579 return -1;
580 }
581
582 @Override
583 public int lastIndexOf(@CheckForNull Object target) {
584 // Overridden to prevent a ton of boxing
585 if (target instanceof Double) {
586 int i = Doubles.lastIndexOf(array, (Double) target, start, end);
587 if (i >= 0) {
588 return i - start;
589 }
590 }
591 return -1;
592 }
593
594 @Override
595 public Double set(int index, Double element) {
596 checkElementIndex(index, size());
597 double oldValue = array[start + index];
598 // checkNotNull for GWT (do not optimize)
599 array[start + index] = checkNotNull(element);
600 return oldValue;
601 }
602
603 @Override
604 public List<Double> subList(int fromIndex, int toIndex) {
605 int size = size();
606 checkPositionIndexes(fromIndex, toIndex, size);
607 if (fromIndex == toIndex) {
608 return Collections.emptyList();
609 }
610 return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
611 }
612
613 @Override
614 public boolean equals(@CheckForNull Object object) {
615 if (object == this) {
616 return true;
617 }
618 if (object instanceof DoubleArrayAsList) {
619 DoubleArrayAsList that = (DoubleArrayAsList) object;
620 int size = size();
621 if (that.size() != size) {
622 return false;
623 }
624 for (int i = 0; i < size; i++) {
625 if (array[start + i] != that.array[that.start + i]) {
626 return false;
627 }
628 }
629 return true;
630 }
631 return super.equals(object);
632 }
633
634 @Override
635 public int hashCode() {
636 int result = 1;
637 for (int i = start; i < end; i++) {
638 result = 31 * result + Doubles.hashCode(array[i]);
639 }
640 return result;
641 }
642
643 @Override
644 public String toString() {
645 StringBuilder builder = new StringBuilder(size() * 12);
646 builder.append('[').append(array[start]);
647 for (int i = start + 1; i < end; i++) {
648 builder.append(", ").append(array[i]);
649 }
650 return builder.append(']').toString();
651 }
652
653 double[] toDoubleArray() {
654 return Arrays.copyOfRange(array, start, end);
655 }
656
657 private static final long serialVersionUID = 0;
658 }
659
660 /**
661 * This is adapted from the regex suggested by {@link Double#valueOf(String)} for prevalidating
662 * inputs. All valid inputs must pass this regex, but it's semantically fine if not all inputs
663 * that pass this regex are valid -- only a performance hit is incurred, not a semantics bug.
664 */
665 @GwtIncompatible // regular expressions
666 static final
667 java.util.regex.Pattern
668 FLOATING_POINT_PATTERN = fpPattern();
669
670 @GwtIncompatible // regular expressions
671 private static
672 java.util.regex.Pattern
673 fpPattern() {
674 /*
675 * We use # instead of * for possessive quantifiers. This lets us strip them out when building
676 * the regex for RE2 (which doesn't support them) but leave them in when building it for
677 * java.util.regex (where we want them in order to avoid catastrophic backtracking).
678 */
679 String decimal = "(?:\\d+#(?:\\.\\d*#)?|\\.\\d+#)";
680 String completeDec = decimal + "(?:[eE][+-]?\\d+#)?[fFdD]?";
681 String hex = "(?:[0-9a-fA-F]+#(?:\\.[0-9a-fA-F]*#)?|\\.[0-9a-fA-F]+#)";
682 String completeHex = "0[xX]" + hex + "[pP][+-]?\\d+#[fFdD]?";
683 String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
684 fpPattern =
685 fpPattern.replace(
686 "#",
687 "+"
688 );
689 return
690 java.util.regex.Pattern
691 .compile(fpPattern);
692 }
693
694 /**
695 * Parses the specified string as a double-precision floating point value. The ASCII character
696 * {@code '-'} (<code>'\u002D'</code>) is recognized as the minus sign.
697 *
698 * <p>Unlike {@link Double#parseDouble(String)}, this method returns {@code null} instead of
699 * throwing an exception if parsing fails. Valid inputs are exactly those accepted by {@link
700 * Double#valueOf(String)}, except that leading and trailing whitespace is not permitted.
701 *
702 * <p>This implementation is likely to be faster than {@code Double.parseDouble} if many failures
703 * are expected.
704 *
705 * @param string the string representation of a {@code double} value
706 * @return the floating point value represented by {@code string}, or {@code null} if {@code
707 * string} has a length of zero or cannot be parsed as a {@code double} value
708 * @throws NullPointerException if {@code string} is {@code null}
709 * @since 14.0
710 */
711 @Beta
712 @GwtIncompatible // regular expressions
713 @CheckForNull
714 public static Double tryParse(String string) {
715 if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
716 // TODO(lowasser): could be potentially optimized, but only with
717 // extensive testing
718 try {
719 return Double.parseDouble(string);
720 } catch (NumberFormatException e) {
721 // Double.parseDouble has changed specs several times, so fall through
722 // gracefully
723 }
724 }
725 return null;
726 }
727 }