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