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