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