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