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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  
22  import com.google.common.annotations.Beta;
23  import com.google.common.annotations.GwtCompatible;
24  import com.google.common.annotations.GwtIncompatible;
25  import java.io.Serializable;
26  import java.util.AbstractList;
27  import java.util.Arrays;
28  import java.util.Collection;
29  import java.util.Collections;
30  import java.util.Comparator;
31  import java.util.List;
32  import java.util.RandomAccess;
33  import javax.annotation.Nullable;
34  
35  /**
36   * Static utility methods pertaining to {@code char} primitives, that are not already found in
37   * either {@link Character} or {@link Arrays}.
38   *
39   * <p>All the operations in this class treat {@code char} values strictly numerically; they are
40   * neither Unicode-aware nor locale-dependent.
41   *
42   * <p>See the Guava User Guide article on
43   * <a href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
44   *
45   * @author Kevin Bourrillion
46   * @since 1.0
47   */
48  @GwtCompatible(emulated = true)
49  public final class Chars {
50    private Chars() {}
51  
52    /**
53     * The number of bytes required to represent a primitive {@code char} value.
54     *
55     * <p><b>Java 8 users:</b> use {@link Character#BYTES} instead.
56     */
57    public static final int BYTES = Character.SIZE / Byte.SIZE;
58  
59    /**
60     * Returns a hash code for {@code value}; equal to the result of invoking
61     * {@code ((Character) value).hashCode()}.
62     *
63     * <p><b>Java 8 users:</b> use {@link Character#hashCode(char)} instead.
64     *
65     * @param value a primitive {@code char} value
66     * @return a hash code for the value
67     */
68    public static int hashCode(char value) {
69      return value;
70    }
71  
72    /**
73     * Returns the {@code char} value that is equal to {@code value}, if possible.
74     *
75     * @param value any value in the range of the {@code char} type
76     * @return the {@code char} value that equals {@code value}
77     * @throws IllegalArgumentException if {@code value} is greater than {@link Character#MAX_VALUE}
78     *     or less than {@link Character#MIN_VALUE}
79     */
80    public static char checkedCast(long value) {
81      char result = (char) value;
82      checkArgument(result == value, "Out of range: %s", value);
83      return result;
84    }
85  
86    /**
87     * Returns the {@code char} nearest in value to {@code value}.
88     *
89     * @param value any {@code long} value
90     * @return the same value cast to {@code char} if it is in the range of the {@code char} type,
91     *     {@link Character#MAX_VALUE} if it is too large, or {@link Character#MIN_VALUE} if it is too
92     *     small
93     */
94    public static char saturatedCast(long value) {
95      if (value > Character.MAX_VALUE) {
96        return Character.MAX_VALUE;
97      }
98      if (value < Character.MIN_VALUE) {
99        return Character.MIN_VALUE;
100     }
101     return (char) value;
102   }
103 
104   /**
105    * Compares the two specified {@code char} values. The sign of the value returned is the same as
106    * that of {@code ((Character) a).compareTo(b)}.
107    *
108    * <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
109    * equivalent {@link Character#compare} method instead.
110    *
111    * @param a the first {@code char} to compare
112    * @param b the second {@code char} to compare
113    * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
114    *     greater than {@code b}; or zero if they are equal
115    */
116   public static int compare(char a, char b) {
117     return a - b; // safe due to restricted range
118   }
119 
120   /**
121    * Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
122    *
123    * @param array an array of {@code char} values, possibly empty
124    * @param target a primitive {@code char} value
125    * @return {@code true} if {@code array[i] == target} for some value of {@code
126    *     i}
127    */
128   public static boolean contains(char[] array, char target) {
129     for (char value : array) {
130       if (value == target) {
131         return true;
132       }
133     }
134     return false;
135   }
136 
137   /**
138    * Returns the index of the first appearance of the value {@code target} in {@code array}.
139    *
140    * @param array an array of {@code char} values, possibly empty
141    * @param target a primitive {@code char} value
142    * @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
143    *     such index exists.
144    */
145   public static int indexOf(char[] array, char target) {
146     return indexOf(array, target, 0, array.length);
147   }
148 
149   // TODO(kevinb): consider making this public
150   private static int indexOf(char[] array, char target, int start, int end) {
151     for (int i = start; i < end; i++) {
152       if (array[i] == target) {
153         return i;
154       }
155     }
156     return -1;
157   }
158 
159   /**
160    * Returns the start position of the first occurrence of the specified {@code
161    * target} within {@code array}, or {@code -1} if there is no such occurrence.
162    *
163    * <p>More formally, returns the lowest index {@code i} such that
164    * {@code Arrays.copyOfRange(array, i, i + target.length)} contains exactly the same elements as
165    * {@code target}.
166    *
167    * @param array the array to search for the sequence {@code target}
168    * @param target the array to search for as a sub-sequence of {@code array}
169    */
170   public static int indexOf(char[] array, char[] target) {
171     checkNotNull(array, "array");
172     checkNotNull(target, "target");
173     if (target.length == 0) {
174       return 0;
175     }
176 
177     outer:
178     for (int i = 0; i < array.length - target.length + 1; i++) {
179       for (int j = 0; j < target.length; j++) {
180         if (array[i + j] != target[j]) {
181           continue outer;
182         }
183       }
184       return i;
185     }
186     return -1;
187   }
188 
189   /**
190    * Returns the index of the last appearance of the value {@code target} in {@code array}.
191    *
192    * @param array an array of {@code char} values, possibly empty
193    * @param target a primitive {@code char} value
194    * @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
195    *     such index exists.
196    */
197   public static int lastIndexOf(char[] array, char target) {
198     return lastIndexOf(array, target, 0, array.length);
199   }
200 
201   // TODO(kevinb): consider making this public
202   private static int lastIndexOf(char[] array, char target, int start, int end) {
203     for (int i = end - 1; i >= start; i--) {
204       if (array[i] == target) {
205         return i;
206       }
207     }
208     return -1;
209   }
210 
211   /**
212    * Returns the least value present in {@code array}.
213    *
214    * @param array a <i>nonempty</i> array of {@code char} values
215    * @return the value present in {@code array} that is less than or equal to every other value in
216    *     the array
217    * @throws IllegalArgumentException if {@code array} is empty
218    */
219   public static char min(char... array) {
220     checkArgument(array.length > 0);
221     char min = array[0];
222     for (int i = 1; i < array.length; i++) {
223       if (array[i] < min) {
224         min = array[i];
225       }
226     }
227     return min;
228   }
229 
230   /**
231    * Returns the greatest value present in {@code array}.
232    *
233    * @param array a <i>nonempty</i> array of {@code char} values
234    * @return the value present in {@code array} that is greater than or equal to every other value
235    *     in the array
236    * @throws IllegalArgumentException if {@code array} is empty
237    */
238   public static char max(char... array) {
239     checkArgument(array.length > 0);
240     char max = array[0];
241     for (int i = 1; i < array.length; i++) {
242       if (array[i] > max) {
243         max = array[i];
244       }
245     }
246     return max;
247   }
248 
249   /**
250    * Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
251    *
252    * <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
253    * unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if
254    * {@code value} is greater than {@code max}, {@code max} is returned.
255    *
256    * @param value the {@code char} value to constrain
257    * @param min the lower bound (inclusive) of the range to constrain {@code value} to
258    * @param max the upper bound (inclusive) of the range to constrain {@code value} to
259    * @throws IllegalArgumentException if {@code min > max}
260    * @since 21.0
261    */
262   @Beta
263   public static char constrainToRange(char value, char min, char max) {
264     checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
265     return value < min ? min : value < max ? value : max;
266   }
267 
268   /**
269    * Returns the values from each provided array combined into a single array. For example,
270    * {@code concat(new char[] {a, b}, new char[] {}, new char[] {c}} returns the array
271    * {@code {a, b, c}}.
272    *
273    * @param arrays zero or more {@code char} arrays
274    * @return a single array containing all the values from the source arrays, in order
275    */
276   public static char[] concat(char[]... arrays) {
277     int length = 0;
278     for (char[] array : arrays) {
279       length += array.length;
280     }
281     char[] result = new char[length];
282     int pos = 0;
283     for (char[] array : arrays) {
284       System.arraycopy(array, 0, result, pos, array.length);
285       pos += array.length;
286     }
287     return result;
288   }
289 
290   /**
291    * Returns a big-endian representation of {@code value} in a 2-element byte array; equivalent to
292    * {@code ByteBuffer.allocate(2).putChar(value).array()}. For example, the input value
293    * {@code '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
294    *
295    * <p>If you need to convert and concatenate several values (possibly even of different types),
296    * use a shared {@link java.nio.ByteBuffer} instance, or use
297    * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
298    */
299   @GwtIncompatible // doesn't work
300   public static byte[] toByteArray(char value) {
301     return new byte[] {(byte) (value >> 8), (byte) value};
302   }
303 
304   /**
305    * Returns the {@code char} value whose big-endian representation is stored in the first 2 bytes
306    * of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getChar()}. For example, the
307    * input byte array {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
308    *
309    * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
310    * flexibility at little cost in readability.
311    *
312    * @throws IllegalArgumentException if {@code bytes} has fewer than 2 elements
313    */
314   @GwtIncompatible // doesn't work
315   public static char fromByteArray(byte[] bytes) {
316     checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
317     return fromBytes(bytes[0], bytes[1]);
318   }
319 
320   /**
321    * Returns the {@code char} value whose byte representation is the given 2 bytes, in big-endian
322    * order; equivalent to {@code Chars.fromByteArray(new byte[] {b1, b2})}.
323    *
324    * @since 7.0
325    */
326   @GwtIncompatible // doesn't work
327   public static char fromBytes(byte b1, byte b2) {
328     return (char) ((b1 << 8) | (b2 & 0xFF));
329   }
330 
331   /**
332    * Returns an array containing the same values as {@code array}, but guaranteed to be of a
333    * specified minimum length. If {@code array} already has a length of at least {@code minLength},
334    * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
335    * returned, containing the values of {@code array}, and zeroes in the remaining places.
336    *
337    * @param array the source array
338    * @param minLength the minimum length the returned array must guarantee
339    * @param padding an extra amount to "grow" the array by if growth is necessary
340    * @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
341    * @return an array containing the values of {@code array}, with guaranteed minimum length
342    *     {@code minLength}
343    */
344   public static char[] ensureCapacity(char[] array, int minLength, int padding) {
345     checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
346     checkArgument(padding >= 0, "Invalid padding: %s", padding);
347     return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
348   }
349 
350   /**
351    * Returns a string containing the supplied {@code char} values separated by {@code separator}.
352    * For example, {@code join("-", '1', '2', '3')} returns the string {@code "1-2-3"}.
353    *
354    * @param separator the text that should appear between consecutive values in the resulting string
355    *     (but not at the start or end)
356    * @param array an array of {@code char} values, possibly empty
357    */
358   public static String join(String separator, char... array) {
359     checkNotNull(separator);
360     int len = array.length;
361     if (len == 0) {
362       return "";
363     }
364 
365     StringBuilder builder = new StringBuilder(len + separator.length() * (len - 1));
366     builder.append(array[0]);
367     for (int i = 1; i < len; i++) {
368       builder.append(separator).append(array[i]);
369     }
370     return builder.toString();
371   }
372 
373   /**
374    * Returns a comparator that compares two {@code char} arrays <a
375    * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
376    * compares, using {@link #compare(char, char)}), the first pair of values that follow any common
377    * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
378    * example, {@code [] < ['a'] < ['a', 'b'] < ['b']}.
379    *
380    * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
381    * support only identity equality), but it is consistent with
382    * {@link Arrays#equals(char[], char[])}.
383    *
384    * @since 2.0
385    */
386   public static Comparator<char[]> lexicographicalComparator() {
387     return LexicographicalComparator.INSTANCE;
388   }
389 
390   private enum LexicographicalComparator implements Comparator<char[]> {
391     INSTANCE;
392 
393     @Override
394     public int compare(char[] left, char[] right) {
395       int minLength = Math.min(left.length, right.length);
396       for (int i = 0; i < minLength; i++) {
397         int result = Chars.compare(left[i], right[i]);
398         if (result != 0) {
399           return result;
400         }
401       }
402       return left.length - right.length;
403     }
404 
405     @Override
406     public String toString() {
407       return "Chars.lexicographicalComparator()";
408     }
409   }
410 
411   /**
412    * Copies a collection of {@code Character} instances into a new array of primitive {@code char}
413    * values.
414    *
415    * <p>Elements are copied from the argument collection as if by {@code
416    * collection.toArray()}. Calling this method is as thread-safe as calling that method.
417    *
418    * @param collection a collection of {@code Character} objects
419    * @return an array containing the same values as {@code collection}, in the same order, converted
420    *     to primitives
421    * @throws NullPointerException if {@code collection} or any of its elements is null
422    */
423   public static char[] toArray(Collection<Character> collection) {
424     if (collection instanceof CharArrayAsList) {
425       return ((CharArrayAsList) collection).toCharArray();
426     }
427 
428     Object[] boxedArray = collection.toArray();
429     int len = boxedArray.length;
430     char[] array = new char[len];
431     for (int i = 0; i < len; i++) {
432       // checkNotNull for GWT (do not optimize)
433       array[i] = (Character) checkNotNull(boxedArray[i]);
434     }
435     return array;
436   }
437 
438   /**
439    * Sorts the elements of {@code array} in descending order.
440    *
441    * @since 23.1
442    */
443   public static void sortDescending(char[] array) {
444     checkNotNull(array);
445     sortDescending(array, 0, array.length);
446   }
447 
448   /**
449    * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
450    * exclusive in descending order.
451    *
452    * @since 23.1
453    */
454   public static void sortDescending(char[] array, int fromIndex, int toIndex) {
455     checkNotNull(array);
456     checkPositionIndexes(fromIndex, toIndex, array.length);
457     Arrays.sort(array, fromIndex, toIndex);
458     reverse(array, fromIndex, toIndex);
459   }
460 
461   /**
462    * Reverses the elements of {@code array}. This is equivalent to {@code
463    * Collections.reverse(Chars.asList(array))}, but is likely to be more efficient.
464    *
465    * @since 23.1
466    */
467   public static void reverse(char[] array) {
468     checkNotNull(array);
469     reverse(array, 0, array.length);
470   }
471 
472   /**
473    * Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
474    * exclusive. This is equivalent to {@code
475    * Collections.reverse(Chars.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
476    * efficient.
477    *
478    * @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
479    *     {@code toIndex > fromIndex}
480    * @since 23.1
481    */
482   public static void reverse(char[] array, int fromIndex, int toIndex) {
483     checkNotNull(array);
484     checkPositionIndexes(fromIndex, toIndex, array.length);
485     for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
486       char tmp = array[i];
487       array[i] = array[j];
488       array[j] = tmp;
489     }
490   }
491 
492   /**
493    * Returns a fixed-size list backed by the specified array, similar to
494    * {@link Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any
495    * attempt to set a value to {@code null} will result in a {@link NullPointerException}.
496    *
497    * <p>The returned list maintains the values, but not the identities, of {@code Character} objects
498    * written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
499    * the returned list is unspecified.
500    *
501    * @param backingArray the array to back the list
502    * @return a list view of the array
503    */
504   public static List<Character> asList(char... backingArray) {
505     if (backingArray.length == 0) {
506       return Collections.emptyList();
507     }
508     return new CharArrayAsList(backingArray);
509   }
510 
511   @GwtCompatible
512   private static class CharArrayAsList extends AbstractList<Character>
513       implements RandomAccess, Serializable {
514     final char[] array;
515     final int start;
516     final int end;
517 
518     CharArrayAsList(char[] array) {
519       this(array, 0, array.length);
520     }
521 
522     CharArrayAsList(char[] 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 Character 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 Character)
548           && Chars.indexOf(array, (Character) target, start, end) != -1;
549     }
550 
551     @Override
552     public int indexOf(Object target) {
553       // Overridden to prevent a ton of boxing
554       if (target instanceof Character) {
555         int i = Chars.indexOf(array, (Character) target, start, end);
556         if (i >= 0) {
557           return i - start;
558         }
559       }
560       return -1;
561     }
562 
563     @Override
564     public int lastIndexOf(Object target) {
565       // Overridden to prevent a ton of boxing
566       if (target instanceof Character) {
567         int i = Chars.lastIndexOf(array, (Character) target, start, end);
568         if (i >= 0) {
569           return i - start;
570         }
571       }
572       return -1;
573     }
574 
575     @Override
576     public Character set(int index, Character element) {
577       checkElementIndex(index, size());
578       char oldValue = array[start + index];
579       // checkNotNull for GWT (do not optimize)
580       array[start + index] = checkNotNull(element);
581       return oldValue;
582     }
583 
584     @Override
585     public List<Character> subList(int fromIndex, int toIndex) {
586       int size = size();
587       checkPositionIndexes(fromIndex, toIndex, size);
588       if (fromIndex == toIndex) {
589         return Collections.emptyList();
590       }
591       return new CharArrayAsList(array, start + fromIndex, start + toIndex);
592     }
593 
594     @Override
595     public boolean equals(@Nullable Object object) {
596       if (object == this) {
597         return true;
598       }
599       if (object instanceof CharArrayAsList) {
600         CharArrayAsList that = (CharArrayAsList) object;
601         int size = size();
602         if (that.size() != size) {
603           return false;
604         }
605         for (int i = 0; i < size; i++) {
606           if (array[start + i] != that.array[that.start + i]) {
607             return false;
608           }
609         }
610         return true;
611       }
612       return super.equals(object);
613     }
614 
615     @Override
616     public int hashCode() {
617       int result = 1;
618       for (int i = start; i < end; i++) {
619         result = 31 * result + Chars.hashCode(array[i]);
620       }
621       return result;
622     }
623 
624     @Override
625     public String toString() {
626       StringBuilder builder = new StringBuilder(size() * 3);
627       builder.append('[').append(array[start]);
628       for (int i = start + 1; i < end; i++) {
629         builder.append(", ").append(array[i]);
630       }
631       return builder.append(']').toString();
632     }
633 
634     char[] toCharArray() {
635       return Arrays.copyOfRange(array, start, end);
636     }
637 
638     private static final long serialVersionUID = 0;
639   }
640 }