001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.primitives;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkElementIndex;
019import static com.google.common.base.Preconditions.checkNotNull;
020import static com.google.common.base.Preconditions.checkPositionIndexes;
021import static java.lang.Float.NEGATIVE_INFINITY;
022import static java.lang.Float.POSITIVE_INFINITY;
023
024import com.google.common.annotations.Beta;
025import com.google.common.annotations.GwtCompatible;
026import com.google.common.annotations.GwtIncompatible;
027import com.google.common.base.Converter;
028import java.io.Serializable;
029import java.util.AbstractList;
030import java.util.Arrays;
031import java.util.Collection;
032import java.util.Collections;
033import java.util.Comparator;
034import java.util.List;
035import java.util.RandomAccess;
036import javax.annotation.CheckForNull;
037import javax.annotation.Nullable;
038
039/**
040 * Static utility methods pertaining to {@code float} primitives, that are not already found in
041 * either {@link Float} or {@link Arrays}.
042 *
043 * <p>See the Guava User Guide article on
044 * <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
045 *
046 * @author Kevin Bourrillion
047 * @since 1.0
048 */
049@GwtCompatible(emulated = true)
050public final class Floats {
051  private Floats() {}
052
053  /**
054   * The number of bytes required to represent a primitive {@code float} value.
055   *
056   * <p><b>Java 8 users:</b> use {@link Float#BYTES} instead.
057   *
058   * @since 10.0
059   */
060  public static final int BYTES = Float.SIZE / Byte.SIZE;
061
062  /**
063   * Returns a hash code for {@code value}; equal to the result of invoking
064   * {@code ((Float) value).hashCode()}.
065   *
066   * <p><b>Java 8 users:</b> use {@link Float#hashCode(float)} instead.
067   *
068   * @param value a primitive {@code float} value
069   * @return a hash code for the value
070   */
071  public static int hashCode(float value) {
072    // TODO(kevinb): is there a better way, that's still gwt-safe?
073    return ((Float) value).hashCode();
074  }
075
076  /**
077   * Compares the two specified {@code float} values using {@link Float#compare(float, float)}. You
078   * may prefer to invoke that method directly; this method exists only for consistency with the
079   * other utilities in this package.
080   *
081   * <p><b>Note:</b> this method simply delegates to the JDK method {@link Float#compare}. It is
082   * provided for consistency with the other primitive types, whose compare methods were not added
083   * to the JDK until JDK 7.
084   *
085   * @param a the first {@code float} to compare
086   * @param b the second {@code float} to compare
087   * @return the result of invoking {@link Float#compare(float, float)}
088   */
089  public static int compare(float a, float b) {
090    return Float.compare(a, b);
091  }
092
093  /**
094   * Returns {@code true} if {@code value} represents a real number. This is equivalent to, but not
095   * necessarily implemented as, {@code !(Float.isInfinite(value) || Float.isNaN(value))}.
096   *
097   * <p><b>Java 8 users:</b> use {@link Float#isFinite(float)} instead.
098   *
099   * @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 values from each provided array combined into a single array. For example,
240   * {@code concat(new float[] {a, b}, new float[] {}, new float[] {c}} returns the array {@code {a,
241   * b, c}}.
242   *
243   * @param arrays zero or more {@code float} arrays
244   * @return a single array containing all the values from the source arrays, in order
245   */
246  public static float[] concat(float[]... arrays) {
247    int length = 0;
248    for (float[] array : arrays) {
249      length += array.length;
250    }
251    float[] result = new float[length];
252    int pos = 0;
253    for (float[] array : arrays) {
254      System.arraycopy(array, 0, result, pos, array.length);
255      pos += array.length;
256    }
257    return result;
258  }
259
260  private static final class FloatConverter extends Converter<String, Float>
261      implements Serializable {
262    static final FloatConverter INSTANCE = new FloatConverter();
263
264    @Override
265    protected Float doForward(String value) {
266      return Float.valueOf(value);
267    }
268
269    @Override
270    protected String doBackward(Float value) {
271      return value.toString();
272    }
273
274    @Override
275    public String toString() {
276      return "Floats.stringConverter()";
277    }
278
279    private Object readResolve() {
280      return INSTANCE;
281    }
282
283    private static final long serialVersionUID = 1;
284  }
285
286  /**
287   * Returns a serializable converter object that converts between strings and floats using
288   * {@link Float#valueOf} and {@link Float#toString()}.
289   *
290   * @since 16.0
291   */
292  @Beta
293  public static Converter<String, Float> stringConverter() {
294    return FloatConverter.INSTANCE;
295  }
296
297  /**
298   * Returns an array containing the same values as {@code array}, but guaranteed to be of a
299   * specified minimum length. If {@code array} already has a length of at least {@code minLength},
300   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
301   * returned, containing the values of {@code array}, and zeroes in the remaining places.
302   *
303   * @param array the source array
304   * @param minLength the minimum length the returned array must guarantee
305   * @param padding an extra amount to "grow" the array by if growth is necessary
306   * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
307   * @return an array containing the values of {@code array}, with guaranteed minimum length
308   *     {@code minLength}
309   */
310  public static float[] ensureCapacity(float[] array, int minLength, int padding) {
311    checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
312    checkArgument(padding >= 0, "Invalid padding: %s", padding);
313    return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
314  }
315
316  /**
317   * Returns a string containing the supplied {@code float} values, converted to strings as
318   * specified by {@link Float#toString(float)}, and separated by {@code separator}. For example,
319   * {@code join("-", 1.0f, 2.0f, 3.0f)} returns the string {@code "1.0-2.0-3.0"}.
320   *
321   * <p>Note that {@link Float#toString(float)} formats {@code float} differently in GWT. In the
322   * previous example, it returns the string {@code
323   * "1-2-3"}.
324   *
325   * @param separator the text that should appear between consecutive values in the resulting string
326   *     (but not at the start or end)
327   * @param array an array of {@code float} values, possibly empty
328   */
329  public static String join(String separator, float... array) {
330    checkNotNull(separator);
331    if (array.length == 0) {
332      return "";
333    }
334
335    // For pre-sizing a builder, just get the right order of magnitude
336    StringBuilder builder = new StringBuilder(array.length * 12);
337    builder.append(array[0]);
338    for (int i = 1; i < array.length; i++) {
339      builder.append(separator).append(array[i]);
340    }
341    return builder.toString();
342  }
343
344  /**
345   * Returns a comparator that compares two {@code float} arrays <a
346   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
347   * compares, using {@link #compare(float, float)}), the first pair of values that follow any
348   * common prefix, or when one array is a prefix of the other, treats the shorter array as the
349   * lesser. For example, {@code [] < [1.0f] < [1.0f, 2.0f] < [2.0f]}.
350   *
351   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
352   * support only identity equality), but it is consistent with
353   * {@link Arrays#equals(float[], float[])}.
354   *
355   * @since 2.0
356   */
357  public static Comparator<float[]> lexicographicalComparator() {
358    return LexicographicalComparator.INSTANCE;
359  }
360
361  private enum LexicographicalComparator implements Comparator<float[]> {
362    INSTANCE;
363
364    @Override
365    public int compare(float[] left, float[] right) {
366      int minLength = Math.min(left.length, right.length);
367      for (int i = 0; i < minLength; i++) {
368        int result = Float.compare(left[i], right[i]);
369        if (result != 0) {
370          return result;
371        }
372      }
373      return left.length - right.length;
374    }
375
376    @Override
377    public String toString() {
378      return "Floats.lexicographicalComparator()";
379    }
380  }
381
382  /**
383   * Returns an array containing each value of {@code collection}, converted to a {@code float}
384   * value in the manner of {@link Number#floatValue}.
385   *
386   * <p>Elements are copied from the argument collection as if by {@code
387   * collection.toArray()}. Calling this method is as thread-safe as calling that method.
388   *
389   * @param collection a collection of {@code Number} instances
390   * @return an array containing the same values as {@code collection}, in the same order, converted
391   *     to primitives
392   * @throws NullPointerException if {@code collection} or any of its elements is null
393   * @since 1.0 (parameter was {@code Collection<Float>} before 12.0)
394   */
395  public static float[] toArray(Collection<? extends Number> collection) {
396    if (collection instanceof FloatArrayAsList) {
397      return ((FloatArrayAsList) collection).toFloatArray();
398    }
399
400    Object[] boxedArray = collection.toArray();
401    int len = boxedArray.length;
402    float[] array = new float[len];
403    for (int i = 0; i < len; i++) {
404      // checkNotNull for GWT (do not optimize)
405      array[i] = ((Number) checkNotNull(boxedArray[i])).floatValue();
406    }
407    return array;
408  }
409
410  /**
411   * Returns a fixed-size list backed by the specified array, similar to
412   * {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any
413   * attempt to set a value to {@code null} will result in a {@link NullPointerException}.
414   *
415   * <p>The returned list maintains the values, but not the identities, of {@code Float} objects
416   * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
417   * the returned list is unspecified.
418   *
419   * <p>The returned list may have unexpected behavior if it contains {@code
420   * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
421   *
422   * @param backingArray the array to back the list
423   * @return a list view of the array
424   */
425  public static List<Float> asList(float... backingArray) {
426    if (backingArray.length == 0) {
427      return Collections.emptyList();
428    }
429    return new FloatArrayAsList(backingArray);
430  }
431
432  @GwtCompatible
433  private static class FloatArrayAsList extends AbstractList<Float>
434      implements RandomAccess, Serializable {
435    final float[] array;
436    final int start;
437    final int end;
438
439    FloatArrayAsList(float[] array) {
440      this(array, 0, array.length);
441    }
442
443    FloatArrayAsList(float[] array, int start, int end) {
444      this.array = array;
445      this.start = start;
446      this.end = end;
447    }
448
449    @Override
450    public int size() {
451      return end - start;
452    }
453
454    @Override
455    public boolean isEmpty() {
456      return false;
457    }
458
459    @Override
460    public Float get(int index) {
461      checkElementIndex(index, size());
462      return array[start + index];
463    }
464
465    @Override
466    public boolean contains(Object target) {
467      // Overridden to prevent a ton of boxing
468      return (target instanceof Float) && Floats.indexOf(array, (Float) target, start, end) != -1;
469    }
470
471    @Override
472    public int indexOf(Object target) {
473      // Overridden to prevent a ton of boxing
474      if (target instanceof Float) {
475        int i = Floats.indexOf(array, (Float) target, start, end);
476        if (i >= 0) {
477          return i - start;
478        }
479      }
480      return -1;
481    }
482
483    @Override
484    public int lastIndexOf(Object target) {
485      // Overridden to prevent a ton of boxing
486      if (target instanceof Float) {
487        int i = Floats.lastIndexOf(array, (Float) target, start, end);
488        if (i >= 0) {
489          return i - start;
490        }
491      }
492      return -1;
493    }
494
495    @Override
496    public Float set(int index, Float element) {
497      checkElementIndex(index, size());
498      float oldValue = array[start + index];
499      // checkNotNull for GWT (do not optimize)
500      array[start + index] = checkNotNull(element);
501      return oldValue;
502    }
503
504    @Override
505    public List<Float> subList(int fromIndex, int toIndex) {
506      int size = size();
507      checkPositionIndexes(fromIndex, toIndex, size);
508      if (fromIndex == toIndex) {
509        return Collections.emptyList();
510      }
511      return new FloatArrayAsList(array, start + fromIndex, start + toIndex);
512    }
513
514    @Override
515    public boolean equals(@Nullable Object object) {
516      if (object == this) {
517        return true;
518      }
519      if (object instanceof FloatArrayAsList) {
520        FloatArrayAsList that = (FloatArrayAsList) object;
521        int size = size();
522        if (that.size() != size) {
523          return false;
524        }
525        for (int i = 0; i < size; i++) {
526          if (array[start + i] != that.array[that.start + i]) {
527            return false;
528          }
529        }
530        return true;
531      }
532      return super.equals(object);
533    }
534
535    @Override
536    public int hashCode() {
537      int result = 1;
538      for (int i = start; i < end; i++) {
539        result = 31 * result + Floats.hashCode(array[i]);
540      }
541      return result;
542    }
543
544    @Override
545    public String toString() {
546      StringBuilder builder = new StringBuilder(size() * 12);
547      builder.append('[').append(array[start]);
548      for (int i = start + 1; i < end; i++) {
549        builder.append(", ").append(array[i]);
550      }
551      return builder.append(']').toString();
552    }
553
554    float[] toFloatArray() {
555      // Arrays.copyOfRange() is not available under GWT
556      int size = size();
557      float[] result = new float[size];
558      System.arraycopy(array, start, result, 0, size);
559      return result;
560    }
561
562    private static final long serialVersionUID = 0;
563  }
564
565  /**
566   * Parses the specified string as a single-precision floating point value. The ASCII character
567   * {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the minus sign.
568   *
569   * <p>Unlike {@link Float#parseFloat(String)}, this method returns {@code null} instead of
570   * throwing an exception if parsing fails. Valid inputs are exactly those accepted by
571   * {@link Float#valueOf(String)}, except that leading and trailing whitespace is not permitted.
572   *
573   * <p>This implementation is likely to be faster than {@code
574   * Float.parseFloat} if many failures are expected.
575   *
576   * @param string the string representation of a {@code float} value
577   * @return the floating point value represented by {@code string}, or {@code null} if
578   *     {@code string} has a length of zero or cannot be parsed as a {@code float} value
579   * @since 14.0
580   */
581  @Beta
582  @Nullable
583  @CheckForNull
584  @GwtIncompatible // regular expressions
585  public static Float tryParse(String string) {
586    if (Doubles.FLOATING_POINT_PATTERN.matcher(string).matches()) {
587      // TODO(lowasser): could be potentially optimized, but only with
588      // extensive testing
589      try {
590        return Float.parseFloat(string);
591      } catch (NumberFormatException e) {
592        // Float.parseFloat has changed specs several times, so fall through
593        // gracefully
594      }
595    }
596    return null;
597  }
598}