001 /*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkArgument;
020 import static com.google.common.base.Preconditions.checkElementIndex;
021 import static com.google.common.base.Preconditions.checkNotNull;
022 import static com.google.common.base.Preconditions.checkPositionIndexes;
023 import static java.lang.Float.NEGATIVE_INFINITY;
024 import static java.lang.Float.POSITIVE_INFINITY;
025
026 import com.google.common.annotations.GwtCompatible;
027
028 import java.io.Serializable;
029 import java.util.AbstractList;
030 import java.util.Arrays;
031 import java.util.Collection;
032 import java.util.Collections;
033 import java.util.Comparator;
034 import java.util.List;
035 import java.util.RandomAccess;
036
037 /**
038 * Static utility methods pertaining to {@code float} primitives, that are not
039 * already found in either {@link Float} or {@link Arrays}.
040 *
041 * <p>See the Guava User Guide article on <a href=
042 * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
043 * primitive utilities</a>.
044 *
045 * @author Kevin Bourrillion
046 * @since 1.0
047 */
048 @GwtCompatible
049 public final class Floats {
050 private Floats() {}
051
052 /**
053 * The number of bytes required to represent a primitive {@code float}
054 * value.
055 *
056 * @since 10.0
057 */
058 public static final int BYTES = Float.SIZE / Byte.SIZE;
059
060 /**
061 * Returns a hash code for {@code value}; equal to the result of invoking
062 * {@code ((Float) value).hashCode()}.
063 *
064 * @param value a primitive {@code float} value
065 * @return a hash code for the value
066 */
067 public static int hashCode(float value) {
068 // TODO(kevinb): is there a better way, that's still gwt-safe?
069 return ((Float) value).hashCode();
070 }
071
072 /**
073 * Compares the two specified {@code float} values using {@link
074 * Float#compare(float, float)}. You may prefer to invoke that method
075 * directly; this method exists only for consistency with the other utilities
076 * in this package.
077 *
078 * @param a the first {@code float} to compare
079 * @param b the second {@code float} to compare
080 * @return the result of invoking {@link Float#compare(float, float)}
081 */
082 public static int compare(float a, float b) {
083 return Float.compare(a, b);
084 }
085
086 /**
087 * Returns {@code true} if {@code value} represents a real number. This is
088 * equivalent to, but not necessarily implemented as,
089 * {@code !(Float.isInfinite(value) || Float.isNaN(value))}.
090 *
091 * @since 10.0
092 */
093 public static boolean isFinite(float value) {
094 return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
095 }
096
097 /**
098 * Returns {@code true} if {@code target} is present as an element anywhere in
099 * {@code array}. Note that this always returns {@code false} when {@code
100 * target} is {@code NaN}.
101 *
102 * @param array an array of {@code float} values, possibly empty
103 * @param target a primitive {@code float} value
104 * @return {@code true} if {@code array[i] == target} for some value of {@code
105 * i}
106 */
107 public static boolean contains(float[] array, float target) {
108 for (float value : array) {
109 if (value == target) {
110 return true;
111 }
112 }
113 return false;
114 }
115
116 /**
117 * Returns the index of the first appearance of the value {@code target} in
118 * {@code array}. Note that this always returns {@code -1} when {@code target}
119 * is {@code NaN}.
120 *
121 * @param array an array of {@code float} values, possibly empty
122 * @param target a primitive {@code float} value
123 * @return the least index {@code i} for which {@code array[i] == target}, or
124 * {@code -1} if no such index exists.
125 */
126 public static int indexOf(float[] array, float target) {
127 return indexOf(array, target, 0, array.length);
128 }
129
130 // TODO(kevinb): consider making this public
131 private static int indexOf(
132 float[] array, float target, int start, int end) {
133 for (int i = start; i < end; i++) {
134 if (array[i] == target) {
135 return i;
136 }
137 }
138 return -1;
139 }
140
141 /**
142 * Returns the start position of the first occurrence of the specified {@code
143 * target} within {@code array}, or {@code -1} if there is no such occurrence.
144 *
145 * <p>More formally, returns the lowest index {@code i} such that {@code
146 * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
147 * the same elements as {@code target}.
148 *
149 * <p>Note that this always returns {@code -1} when {@code target} contains
150 * {@code NaN}.
151 *
152 * @param array the array to search for the sequence {@code target}
153 * @param target the array to search for as a sub-sequence of {@code array}
154 */
155 public static int indexOf(float[] array, float[] target) {
156 checkNotNull(array, "array");
157 checkNotNull(target, "target");
158 if (target.length == 0) {
159 return 0;
160 }
161
162 outer:
163 for (int i = 0; i < array.length - target.length + 1; i++) {
164 for (int j = 0; j < target.length; j++) {
165 if (array[i + j] != target[j]) {
166 continue outer;
167 }
168 }
169 return i;
170 }
171 return -1;
172 }
173
174 /**
175 * Returns the index of the last appearance of the value {@code target} in
176 * {@code array}. Note that this always returns {@code -1} when {@code target}
177 * is {@code NaN}.
178 *
179 * @param array an array of {@code float} values, possibly empty
180 * @param target a primitive {@code float} value
181 * @return the greatest index {@code i} for which {@code array[i] == target},
182 * or {@code -1} if no such index exists.
183 */
184 public static int lastIndexOf(float[] array, float target) {
185 return lastIndexOf(array, target, 0, array.length);
186 }
187
188 // TODO(kevinb): consider making this public
189 private static int lastIndexOf(
190 float[] array, float target, int start, int end) {
191 for (int i = end - 1; i >= start; i--) {
192 if (array[i] == target) {
193 return i;
194 }
195 }
196 return -1;
197 }
198
199 /**
200 * Returns the least value present in {@code array}, using the same rules of
201 * comparison as {@link Math#min(float, float)}.
202 *
203 * @param array a <i>nonempty</i> array of {@code float} values
204 * @return the value present in {@code array} that is less than or equal to
205 * every other value in the array
206 * @throws IllegalArgumentException if {@code array} is empty
207 */
208 public static float min(float... array) {
209 checkArgument(array.length > 0);
210 float min = array[0];
211 for (int i = 1; i < array.length; i++) {
212 min = Math.min(min, array[i]);
213 }
214 return min;
215 }
216
217 /**
218 * Returns the greatest value present in {@code array}, using the same rules
219 * of comparison as {@link Math#min(float, float)}.
220 *
221 * @param array a <i>nonempty</i> array of {@code float} values
222 * @return the value present in {@code array} that is greater than or equal to
223 * every other value in the array
224 * @throws IllegalArgumentException if {@code array} is empty
225 */
226 public static float max(float... array) {
227 checkArgument(array.length > 0);
228 float max = array[0];
229 for (int i = 1; i < array.length; i++) {
230 max = Math.max(max, array[i]);
231 }
232 return max;
233 }
234
235 /**
236 * Returns the values from each provided array combined into a single array.
237 * For example, {@code concat(new float[] {a, b}, new float[] {}, new
238 * float[] {c}} returns the array {@code {a, b, c}}.
239 *
240 * @param arrays zero or more {@code float} arrays
241 * @return a single array containing all the values from the source arrays, in
242 * order
243 */
244 public static float[] concat(float[]... arrays) {
245 int length = 0;
246 for (float[] array : arrays) {
247 length += array.length;
248 }
249 float[] result = new float[length];
250 int pos = 0;
251 for (float[] array : arrays) {
252 System.arraycopy(array, 0, result, pos, array.length);
253 pos += array.length;
254 }
255 return result;
256 }
257
258 /**
259 * Returns an array containing the same values as {@code array}, but
260 * guaranteed to be of a specified minimum length. If {@code array} already
261 * has a length of at least {@code minLength}, it is returned directly.
262 * Otherwise, a new array of size {@code minLength + padding} is returned,
263 * containing the values of {@code array}, and zeroes in the remaining places.
264 *
265 * @param array the source array
266 * @param minLength the minimum length the returned array must guarantee
267 * @param padding an extra amount to "grow" the array by if growth is
268 * necessary
269 * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
270 * negative
271 * @return an array containing the values of {@code array}, with guaranteed
272 * minimum length {@code minLength}
273 */
274 public static float[] ensureCapacity(
275 float[] array, int minLength, int padding) {
276 checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
277 checkArgument(padding >= 0, "Invalid padding: %s", padding);
278 return (array.length < minLength)
279 ? copyOf(array, minLength + padding)
280 : array;
281 }
282
283 // Arrays.copyOf() requires Java 6
284 private static float[] copyOf(float[] original, int length) {
285 float[] copy = new float[length];
286 System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
287 return copy;
288 }
289
290 /**
291 * Returns a string containing the supplied {@code float} values, converted
292 * to strings as specified by {@link Float#toString(float)}, and separated by
293 * {@code separator}. For example, {@code join("-", 1.0f, 2.0f, 3.0f)}
294 * returns the string {@code "1.0-2.0-3.0"}.
295 *
296 * <p>Note that {@link Float#toString(float)} formats {@code float}
297 * differently in GWT. In the previous example, it returns the string {@code
298 * "1-2-3"}.
299 *
300 * @param separator the text that should appear between consecutive values in
301 * the resulting string (but not at the start or end)
302 * @param array an array of {@code float} values, possibly empty
303 */
304 public static String join(String separator, float... array) {
305 checkNotNull(separator);
306 if (array.length == 0) {
307 return "";
308 }
309
310 // For pre-sizing a builder, just get the right order of magnitude
311 StringBuilder builder = new StringBuilder(array.length * 12);
312 builder.append(array[0]);
313 for (int i = 1; i < array.length; i++) {
314 builder.append(separator).append(array[i]);
315 }
316 return builder.toString();
317 }
318
319 /**
320 * Returns a comparator that compares two {@code float} arrays
321 * lexicographically. That is, it compares, using {@link
322 * #compare(float, float)}), the first pair of values that follow any
323 * common prefix, or when one array is a prefix of the other, treats the
324 * shorter array as the lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f]
325 * < [2.0f]}.
326 *
327 * <p>The returned comparator is inconsistent with {@link
328 * Object#equals(Object)} (since arrays support only identity equality), but
329 * it is consistent with {@link Arrays#equals(float[], float[])}.
330 *
331 * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
332 * Lexicographical order article at Wikipedia</a>
333 * @since 2.0
334 */
335 public static Comparator<float[]> lexicographicalComparator() {
336 return LexicographicalComparator.INSTANCE;
337 }
338
339 private enum LexicographicalComparator implements Comparator<float[]> {
340 INSTANCE;
341
342 @Override
343 public int compare(float[] left, float[] right) {
344 int minLength = Math.min(left.length, right.length);
345 for (int i = 0; i < minLength; i++) {
346 int result = Floats.compare(left[i], right[i]);
347 if (result != 0) {
348 return result;
349 }
350 }
351 return left.length - right.length;
352 }
353 }
354
355 /**
356 * Returns an array containing each value of {@code collection}, converted to
357 * a {@code float} value in the manner of {@link Number#floatValue}.
358 *
359 * <p>Elements are copied from the argument collection as if by {@code
360 * collection.toArray()}. Calling this method is as thread-safe as calling
361 * that method.
362 *
363 * @param collection a collection of {@code Number} instances
364 * @return an array containing the same values as {@code collection}, in the
365 * same order, converted to primitives
366 * @throws NullPointerException if {@code collection} or any of its elements
367 * is null
368 * @since 1.0 (parameter was {@code Collection<Float>} before 12.0)
369 */
370 public static float[] toArray(Collection<? extends Number> collection) {
371 if (collection instanceof FloatArrayAsList) {
372 return ((FloatArrayAsList) collection).toFloatArray();
373 }
374
375 Object[] boxedArray = collection.toArray();
376 int len = boxedArray.length;
377 float[] array = new float[len];
378 for (int i = 0; i < len; i++) {
379 // checkNotNull for GWT (do not optimize)
380 array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue();
381 }
382 return array;
383 }
384
385 /**
386 * Returns a fixed-size list backed by the specified array, similar to {@link
387 * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
388 * but any attempt to set a value to {@code null} will result in a {@link
389 * NullPointerException}.
390 *
391 * <p>The returned list maintains the values, but not the identities, of
392 * {@code Float} objects written to or read from it. For example, whether
393 * {@code list.get(0) == list.get(0)} is true for the returned list is
394 * unspecified.
395 *
396 * <p>The returned list may have unexpected behavior if it contains {@code
397 * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
398 *
399 * @param backingArray the array to back the list
400 * @return a list view of the array
401 */
402 public static List<Float> asList(float... backingArray) {
403 if (backingArray.length == 0) {
404 return Collections.emptyList();
405 }
406 return new FloatArrayAsList(backingArray);
407 }
408
409 @GwtCompatible
410 private static class FloatArrayAsList extends AbstractList<Float>
411 implements RandomAccess, Serializable {
412 final float[] array;
413 final int start;
414 final int end;
415
416 FloatArrayAsList(float[] array) {
417 this(array, 0, array.length);
418 }
419
420 FloatArrayAsList(float[] array, int start, int end) {
421 this.array = array;
422 this.start = start;
423 this.end = end;
424 }
425
426 @Override public int size() {
427 return end - start;
428 }
429
430 @Override public boolean isEmpty() {
431 return false;
432 }
433
434 @Override public Float get(int index) {
435 checkElementIndex(index, size());
436 return array[start + index];
437 }
438
439 @Override public boolean contains(Object target) {
440 // Overridden to prevent a ton of boxing
441 return (target instanceof Float)
442 && Floats.indexOf(array, (Float) target, start, end) != -1;
443 }
444
445 @Override public int indexOf(Object target) {
446 // Overridden to prevent a ton of boxing
447 if (target instanceof Float) {
448 int i = Floats.indexOf(array, (Float) target, start, end);
449 if (i >= 0) {
450 return i - start;
451 }
452 }
453 return -1;
454 }
455
456 @Override public int lastIndexOf(Object target) {
457 // Overridden to prevent a ton of boxing
458 if (target instanceof Float) {
459 int i = Floats.lastIndexOf(array, (Float) target, start, end);
460 if (i >= 0) {
461 return i - start;
462 }
463 }
464 return -1;
465 }
466
467 @Override public Float set(int index, Float element) {
468 checkElementIndex(index, size());
469 float oldValue = array[start + index];
470 array[start + index] = checkNotNull(element); // checkNotNull for GWT (do not optimize)
471 return oldValue;
472 }
473
474 @Override public List<Float> subList(int fromIndex, int toIndex) {
475 int size = size();
476 checkPositionIndexes(fromIndex, toIndex, size);
477 if (fromIndex == toIndex) {
478 return Collections.emptyList();
479 }
480 return new FloatArrayAsList(array, start + fromIndex, start + toIndex);
481 }
482
483 @Override public boolean equals(Object object) {
484 if (object == this) {
485 return true;
486 }
487 if (object instanceof FloatArrayAsList) {
488 FloatArrayAsList that = (FloatArrayAsList) object;
489 int size = size();
490 if (that.size() != size) {
491 return false;
492 }
493 for (int i = 0; i < size; i++) {
494 if (array[start + i] != that.array[that.start + i]) {
495 return false;
496 }
497 }
498 return true;
499 }
500 return super.equals(object);
501 }
502
503 @Override public int hashCode() {
504 int result = 1;
505 for (int i = start; i < end; i++) {
506 result = 31 * result + Floats.hashCode(array[i]);
507 }
508 return result;
509 }
510
511 @Override public String toString() {
512 StringBuilder builder = new StringBuilder(size() * 12);
513 builder.append('[').append(array[start]);
514 for (int i = start + 1; i < end; i++) {
515 builder.append(", ").append(array[i]);
516 }
517 return builder.append(']').toString();
518 }
519
520 float[] toFloatArray() {
521 // Arrays.copyOfRange() requires Java 6
522 int size = size();
523 float[] result = new float[size];
524 System.arraycopy(array, start, result, 0, size);
525 return result;
526 }
527
528 private static final long serialVersionUID = 0;
529 }
530 }