    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
    024    import com.google.common.annotations.GwtCompatible;
    025    import com.google.common.annotations.GwtIncompatible;
    026
    027    import java.io.Serializable;
    028    import java.util.AbstractList;
    029    import java.util.Arrays;
    030    import java.util.Collection;
    031    import java.util.Collections;
    032    import java.util.Comparator;
    033    import java.util.List;
    034    import java.util.RandomAccess;
    035
    036    /**
    037     * Static utility methods pertaining to {@code char} primitives, that are not
    038     * already found in either {@link Character} or {@link Arrays}.
    039     *
    040     * <p>All the operations in this class treat {@code char} values strictly
    041     * numerically; they are neither Unicode-aware nor locale-dependent.
    042     *
    043     * @author Kevin Bourrillion
    044     * @since 1.0
    045     */
    046    @GwtCompatible(emulated = true)
    047    public final class Chars {
    048      private Chars() {}
    049
    050      /**
    051       * The number of bytes required to represent a primitive {@code char}
    052       * value.
    053       */
    054      public static final int BYTES = Character.SIZE / Byte.SIZE;
    055
    056      /**
    057       * Returns a hash code for {@code value}; equal to the result of invoking
    058       * {@code ((Character) value).hashCode()}.
    059       *
    060       * @param value a primitive {@code char} value
    061       * @return a hash code for the value
    062       */
    063      public static int hashCode(char value) {
    064        return value;
    065      }
    066
    067      /**
    068       * Returns the {@code char} value that is equal to {@code value}, if possible.
    069       *
    070       * @param value any value in the range of the {@code char} type
    071       * @return the {@code char} value that equals {@code value}
    072       * @throws IllegalArgumentException if {@code value} is greater than {@link
    073       *     Character#MAX_VALUE} or less than {@link Character#MIN_VALUE}
    074       */
    075      public static char checkedCast(long value) {
    076        char result = (char) value;
    077        checkArgument(result == value, "Out of range: %s", value);
    078        return result;
    079      }
    080
    081      /**
    082       * Returns the {@code char} nearest in value to {@code value}.
    083       *
    084       * @param value any {@code long} value
    085       * @return the same value cast to {@code char} if it is in the range of the
    086       *     {@code char} type, {@link Character#MAX_VALUE} if it is too large,
    087       *     or {@link Character#MIN_VALUE} if it is too small
    088       */
    089      public static char saturatedCast(long value) {
    090        if (value > Character.MAX_VALUE) {
    091          return Character.MAX_VALUE;
    092        }
    093        if (value < Character.MIN_VALUE) {
    094          return Character.MIN_VALUE;
    095        }
    096        return (char) value;
    097      }
    098
    099      /**
    100       * Compares the two specified {@code char} values. The sign of the value
    101       * returned is the same as that of {@code ((Character) a).compareTo(b)}.
    102       *
    103       * @param a the first {@code char} to compare
    104       * @param b the second {@code char} to compare
    105       * @return a negative value if {@code a} is less than {@code b}; a positive
    106       *     value if {@code a} is greater than {@code b}; or zero if they are equal
    107       */
    108      public static int compare(char a, char b) {
    109        return a - b; // safe due to restricted range
    110      }
    111
    112      /**
    113       * Returns {@code true} if {@code target} is present as an element anywhere in
    114       * {@code array}.
    115       *
    116       * @param array an array of {@code char} values, possibly empty
    117       * @param target a primitive {@code char} value
    118       * @return {@code true} if {@code array[i] == target} for some value of {@code
    119       *     i}
    120       */
    121      public static boolean contains(char[] array, char target) {
    122        for (char value : array) {
    123          if (value == target) {
    124            return true;
    125          }
    126        }
    127        return false;
    128      }
    129
    130      /**
    131       * Returns the index of the first appearance of the value {@code target} in
    132       * {@code array}.
    133       *
    134       * @param array an array of {@code char} values, possibly empty
    135       * @param target a primitive {@code char} value
    136       * @return the least index {@code i} for which {@code array[i] == target}, or
    137       *     {@code -1} if no such index exists.
    138       */
    139      public static int indexOf(char[] array, char target) {
    140        return indexOf(array, target, 0, array.length);
    141      }
    142
    143      // TODO(kevinb): consider making this public
    144      private static int indexOf(
    145          char[] array, char target, int start, int end) {
    146        for (int i = start; i < end; i++) {
    147          if (array[i] == target) {
    148            return i;
    149          }
    150        }
    151        return -1;
    152      }
    153
    154      /**
    155       * Returns the start position of the first occurrence of the specified {@code
    156       * target} within {@code array}, or {@code -1} if there is no such occurrence.
    157       *
    158       * <p>More formally, returns the lowest index {@code i} such that {@code
    159       * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
    160       * the same elements as {@code target}.
    161       *
    162       * @param array the array to search for the sequence {@code target}
    163       * @param target the array to search for as a sub-sequence of {@code array}
    164       */
    165      public static int indexOf(char[] array, char[] target) {
    166        checkNotNull(array, "array");
    167        checkNotNull(target, "target");
    168        if (target.length == 0) {
    169          return 0;
    170        }
    171
    172        outer:
    173        for (int i = 0; i < array.length - target.length + 1; i++) {
    174          for (int j = 0; j < target.length; j++) {
    175            if (array[i + j] != target[j]) {
    176              continue outer;
    177            }
    178          }
    179          return i;
    180        }
    181        return -1;
    182      }
    183
    184      /**
    185       * Returns the index of the last appearance of the value {@code target} in
    186       * {@code array}.
    187       *
    188       * @param array an array of {@code char} values, possibly empty
    189       * @param target a primitive {@code char} value
    190       * @return the greatest index {@code i} for which {@code array[i] == target},
    191       *     or {@code -1} if no such index exists.
    192       */
    193      public static int lastIndexOf(char[] array, char target) {
    194        return lastIndexOf(array, target, 0, array.length);
    195      }
    196
    197      // TODO(kevinb): consider making this public
    198      private static int lastIndexOf(
    199          char[] array, char target, int start, int end) {
    200        for (int i = end - 1; i >= start; i--) {
    201          if (array[i] == target) {
    202            return i;
    203          }
    204        }
    205        return -1;
    206      }
    207
    208      /**
    209       * Returns the least value present in {@code array}.
    210       *
    211       * @param array a <i>nonempty</i> array of {@code char} values
    212       * @return the value present in {@code array} that is less than or equal to
    213       *     every other value in the array
    214       * @throws IllegalArgumentException if {@code array} is empty
    215       */
    216      public static char min(char... array) {
    217        checkArgument(array.length > 0);
    218        char min = array[0];
    219        for (int i = 1; i < array.length; i++) {
    220          if (array[i] < min) {
    221            min = array[i];
    222          }
    223        }
    224        return min;
    225      }
    226
    227      /**
    228       * Returns the greatest value present in {@code array}.
    229       *
    230       * @param array a <i>nonempty</i> array of {@code char} values
    231       * @return the value present in {@code array} that is greater than or equal to
    232       *     every other value in the array
    233       * @throws IllegalArgumentException if {@code array} is empty
    234       */
    235      public static char max(char... array) {
    236        checkArgument(array.length > 0);
    237        char max = array[0];
    238        for (int i = 1; i < array.length; i++) {
    239          if (array[i] > max) {
    240            max = array[i];
    241          }
    242        }
    243        return max;
    244      }
    245
    246      /**
    247       * Returns the values from each provided array combined into a single array.
    248       * For example, {@code concat(new char[] {a, b}, new char[] {}, new
    249       * char[] {c}} returns the array {@code {a, b, c}}.
    250       *
    251       * @param arrays zero or more {@code char} arrays
    252       * @return a single array containing all the values from the source arrays, in
    253       *     order
    254       */
    255      public static char[] concat(char[]... arrays) {
    256        int length = 0;
    257        for (char[] array : arrays) {
    258          length += array.length;
    259        }
    260        char[] result = new char[length];
    261        int pos = 0;
    262        for (char[] array : arrays) {
    263          System.arraycopy(array, 0, result, pos, array.length);
    264          pos += array.length;
    265        }
    266        return result;
    267      }
    268
    269      /**
    270       * Returns a big-endian representation of {@code value} in a 2-element byte
    271       * array; equivalent to {@code
    272       * ByteBuffer.allocate(2).putChar(value).array()}.  For example, the input
    273       * value {@code '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
    274       *
    275       * <p>If you need to convert and concatenate several values (possibly even of
    276       * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
    277       * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
    278       * buffer.
    279       */
    280      @GwtIncompatible("doesn't work")
    281      public static byte[] toByteArray(char value) {
    282        return new byte[] {
    283            (byte) (value >> 8),
    284            (byte) value};
    285      }
    286
    287      /**
    288       * Returns the {@code char} value whose big-endian representation is
    289       * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
    290       * ByteBuffer.wrap(bytes).getChar()}. For example, the input byte array
    291       * {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
    292       *
    293       * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
    294       * library exposes much more flexibility at little cost in readability.
    295       *
    296       * @throws IllegalArgumentException if {@code bytes} has fewer than 2
    297       *     elements
    298       */
    299      @GwtIncompatible("doesn't work")
    300      public static char fromByteArray(byte[] bytes) {
    301        checkArgument(bytes.length >= BYTES,
    302            "array too small: %s < %s", bytes.length, BYTES);
    303        return fromBytes(bytes[0], bytes[1]);
    304      }
    305
    306      /**
    307       * Returns the {@code char} value whose byte representation is the given 2
    308       * bytes, in big-endian order; equivalent to {@code Chars.fromByteArray(new
    309       * byte[] {b1, b2})}.
    310       *
    311       * @since 7.0
    312       */
    313      @GwtIncompatible("doesn't work")
    314      public static char fromBytes(byte b1, byte b2) {
    315        return (char) ((b1 << 8) | (b2 & 0xFF));
    316      }
    317
    318      /**
    319       * Returns an array containing the same values as {@code array}, but
    320       * guaranteed to be of a specified minimum length. If {@code array} already
    321       * has a length of at least {@code minLength}, it is returned directly.
    322       * Otherwise, a new array of size {@code minLength + padding} is returned,
    323       * containing the values of {@code array}, and zeroes in the remaining places.
    324       *
    325       * @param array the source array
    326       * @param minLength the minimum length the returned array must guarantee
    327       * @param padding an extra amount to "grow" the array by if growth is
    328       *     necessary
    329       * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
    330       *     negative
    331       * @return an array containing the values of {@code array}, with guaranteed
    332       *     minimum length {@code minLength}
    333       */
    334      public static char[] ensureCapacity(
    335          char[] array, int minLength, int padding) {
    336        checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
    337        checkArgument(padding >= 0, "Invalid padding: %s", padding);
    338        return (array.length < minLength)
    339            ? copyOf(array, minLength + padding)
    340            : array;
    341      }
    342
    343      // Arrays.copyOf() requires Java 6
    344      private static char[] copyOf(char[] original, int length) {
    345        char[] copy = new char[length];
    346        System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
    347        return copy;
    348      }
    349
    350      /**
    351       * Returns a string containing the supplied {@code char} values separated
    352       * by {@code separator}. For example, {@code join("-", '1', '2', '3')} returns
    353       * the string {@code "1-2-3"}.
    354       *
    355       * @param separator the text that should appear between consecutive values in
    356       *     the resulting string (but not at the start or end)
    357       * @param array an array of {@code char} values, possibly empty
    358       */
    359      public static String join(String separator, char... array) {
    360        checkNotNull(separator);
    361        int len = array.length;
    362        if (len == 0) {
    363          return "";
    364        }
    365
    366        StringBuilder builder
    367            = new StringBuilder(len + separator.length() * (len - 1));
    368        builder.append(array[0]);
    369        for (int i = 1; i < len; i++) {
    370          builder.append(separator).append(array[i]);
    371        }
    372        return builder.toString();
    373      }
    374
    375      /**
    376       * Returns a comparator that compares two {@code char} arrays
    377       * lexicographically. That is, it compares, using {@link
    378       * #compare(char, char)}), the first pair of values that follow any
    379       * common prefix, or when one array is a prefix of the other, treats the
    380       * shorter array as the lesser. For example,
    381       * {@code [] < ['a'] < ['a', 'b'] < ['b']}.
    382       *
    383       * <p>The returned comparator is inconsistent with {@link
    384       * Object#equals(Object)} (since arrays support only identity equality), but
    385       * it is consistent with {@link Arrays#equals(char[], char[])}.
    386       *
    387       * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
    388       *     Lexicographical order article at Wikipedia</a>
    389       * @since 2.0
    390       */
    391      public static Comparator<char[]> lexicographicalComparator() {
    392        return LexicographicalComparator.INSTANCE;
    393      }
    394
    395      private enum LexicographicalComparator implements Comparator<char[]> {
    396        INSTANCE;
    397
    398        @Override
    399        public int compare(char[] left, char[] right) {
    400          int minLength = Math.min(left.length, right.length);
    401          for (int i = 0; i < minLength; i++) {
    402            int result = Chars.compare(left[i], right[i]);
    403            if (result != 0) {
    404              return result;
    405            }
    406          }
    407          return left.length - right.length;
    408        }
    409      }
    410
    411      /**
    412       * Copies a collection of {@code Character} instances into a new array of
    413       * primitive {@code char} 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
    417       * that method.
    418       *
    419       * @param collection a collection of {@code Character} objects
    420       * @return an array containing the same values as {@code collection}, in the
    421       *     same order, converted to primitives
    422       * @throws NullPointerException if {@code collection} or any of its elements
    423       *     is null
    424       */
    425      public static char[] toArray(Collection<Character> collection) {
    426        if (collection instanceof CharArrayAsList) {
    427          return ((CharArrayAsList) collection).toCharArray();
    428        }
    429
    430        Object[] boxedArray = collection.toArray();
    431        int len = boxedArray.length;
    432        char[] array = new char[len];
    433        for (int i = 0; i < len; i++) {
    434          // checkNotNull for GWT (do not optimize)
    435          array[i] = (Character) checkNotNull(boxedArray[i]);
    436        }
    437        return array;
    438      }
    439
    440      /**
    441       * Returns a fixed-size list backed by the specified array, similar to {@link
    442       * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
    443       * but any attempt to set a value to {@code null} will result in a {@link
    444       * NullPointerException}.
    445       *
    446       * <p>The returned list maintains the values, but not the identities, of
    447       * {@code Character} objects written to or read from it.  For example, whether
    448       * {@code list.get(0) == list.get(0)} is true for the returned list is
    449       * unspecified.
    450       *
    451       * @param backingArray the array to back the list
    452       * @return a list view of the array
    453       */
    454      public static List<Character> asList(char... backingArray) {
    455        if (backingArray.length == 0) {
    456          return Collections.emptyList();
    457        }
    458        return new CharArrayAsList(backingArray);
    459      }
    460
    461      @GwtCompatible
    462      private static class CharArrayAsList extends AbstractList<Character>
    463          implements RandomAccess, Serializable {
    464        final char[] array;
    465        final int start;
    466        final int end;
    467
    468        CharArrayAsList(char[] array) {
    469          this(array, 0, array.length);
    470        }
    471
    472        CharArrayAsList(char[] array, int start, int end) {
    473          this.array = array;
    474          this.start = start;
    475          this.end = end;
    476        }
    477
    478        @Override public int size() {
    479          return end - start;
    480        }
    481
    482        @Override public boolean isEmpty() {
    483          return false;
    484        }
    485
    486        @Override public Character get(int index) {
    487          checkElementIndex(index, size());
    488          return array[start + index];
    489        }
    490
    491        @Override public boolean contains(Object target) {
    492          // Overridden to prevent a ton of boxing
    493          return (target instanceof Character)
    494              && Chars.indexOf(array, (Character) target, start, end) != -1;
    495        }
    496
    497        @Override public int indexOf(Object target) {
    498          // Overridden to prevent a ton of boxing
    499          if (target instanceof Character) {
    500            int i = Chars.indexOf(array, (Character) target, start, end);
    501            if (i >= 0) {
    502              return i - start;
    503            }
    504          }
    505          return -1;
    506        }
    507
    508        @Override public int lastIndexOf(Object target) {
    509          // Overridden to prevent a ton of boxing
    510          if (target instanceof Character) {
    511            int i = Chars.lastIndexOf(array, (Character) target, start, end);
    512            if (i >= 0) {
    513              return i - start;
    514            }
    515          }
    516          return -1;
    517        }
    518
    519        @Override public Character set(int index, Character element) {
    520          checkElementIndex(index, size());
    521          char oldValue = array[start + index];
    522          array[start + index] = checkNotNull(element);  // checkNotNull for GWT (do not optimize)
    523          return oldValue;
    524        }
    525
    526        @Override public List<Character> subList(int fromIndex, int toIndex) {
    527          int size = size();
    528          checkPositionIndexes(fromIndex, toIndex, size);
    529          if (fromIndex == toIndex) {
    530            return Collections.emptyList();
    531          }
    532          return new CharArrayAsList(array, start + fromIndex, start + toIndex);
    533        }
    534
    535        @Override public boolean equals(Object object) {
    536          if (object == this) {
    537            return true;
    538          }
    539          if (object instanceof CharArrayAsList) {
    540            CharArrayAsList that = (CharArrayAsList) object;
    541            int size = size();
    542            if (that.size() != size) {
    543              return false;
    544            }
    545            for (int i = 0; i < size; i++) {
    546              if (array[start + i] != that.array[that.start + i]) {
    547                return false;
    548              }
    549            }
    550            return true;
    551          }
    552          return super.equals(object);
    553        }
    554
    555        @Override public int hashCode() {
    556          int result = 1;
    557          for (int i = start; i < end; i++) {
    558            result = 31 * result + Chars.hashCode(array[i]);
    559          }
    560          return result;
    561        }
    562
    563        @Override public String toString() {
    564          StringBuilder builder = new StringBuilder(size() * 3);
    565          builder.append('[').append(array[start]);
    566          for (int i = start + 1; i < end; i++) {
    567            builder.append(", ").append(array[i]);
    568          }
    569          return builder.append(']').toString();
    570        }
    571
    572        char[] toCharArray() {
    573          // Arrays.copyOfRange() requires Java 6
    574          int size = size();
    575          char[] result = new char[size];
    576          System.arraycopy(array, start, result, 0, size);
    577          return result;
    578        }
    579
    580        private static final long serialVersionUID = 0;
    581      }
    582    }