Chars.java
/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.primitives;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.AbstractList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.CheckForNull;
/**
* Static utility methods pertaining to {@code char} primitives, that are not already found in
* either {@link Character} or {@link Arrays}.
*
* <p>All the operations in this class treat {@code char} values strictly numerically; they are
* neither Unicode-aware nor locale-dependent.
*
* <p>See the Guava User Guide article on <a
* href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
*
* @author Kevin Bourrillion
* @since 1.0
*/
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Chars {
private Chars() {}
/**
* The number of bytes required to represent a primitive {@code char} value.
*
* <p><b>Java 8 users:</b> use {@link Character#BYTES} instead.
*/
public static final int BYTES = Character.SIZE / Byte.SIZE;
/**
* Returns a hash code for {@code value}; equal to the result of invoking {@code ((Character)
* value).hashCode()}.
*
* <p><b>Java 8 users:</b> use {@link Character#hashCode(char)} instead.
*
* @param value a primitive {@code char} value
* @return a hash code for the value
*/
public static int hashCode(char value) {
return value;
}
/**
* Returns the {@code char} value that is equal to {@code value}, if possible.
*
* @param value any value in the range of the {@code char} type
* @return the {@code char} value that equals {@code value}
* @throws IllegalArgumentException if {@code value} is greater than {@link Character#MAX_VALUE}
* or less than {@link Character#MIN_VALUE}
*/
public static char checkedCast(long value) {
char result = (char) value;
checkArgument(result == value, "Out of range: %s", value);
return result;
}
/**
* Returns the {@code char} nearest in value to {@code value}.
*
* @param value any {@code long} value
* @return the same value cast to {@code char} if it is in the range of the {@code char} type,
* {@link Character#MAX_VALUE} if it is too large, or {@link Character#MIN_VALUE} if it is too
* small
*/
public static char saturatedCast(long value) {
if (value > Character.MAX_VALUE) {
return Character.MAX_VALUE;
}
if (value < Character.MIN_VALUE) {
return Character.MIN_VALUE;
}
return (char) value;
}
/**
* Compares the two specified {@code char} values. The sign of the value returned is the same as
* that of {@code ((Character) a).compareTo(b)}.
*
* <p><b>Note for Java 7 and later:</b> this method should be treated as deprecated; use the
* equivalent {@link Character#compare} method instead.
*
* @param a the first {@code char} to compare
* @param b the second {@code char} to compare
* @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
* greater than {@code b}; or zero if they are equal
*/
public static int compare(char a, char b) {
return a - b; // safe due to restricted range
}
/**
* Returns {@code true} if {@code target} is present as an element anywhere in {@code array}.
*
* @param array an array of {@code char} values, possibly empty
* @param target a primitive {@code char} value
* @return {@code true} if {@code array[i] == target} for some value of {@code i}
*/
public static boolean contains(char[] array, char target) {
for (char value : array) {
if (value == target) {
return true;
}
}
return false;
}
/**
* Returns the index of the first appearance of the value {@code target} in {@code array}.
*
* @param array an array of {@code char} values, possibly empty
* @param target a primitive {@code char} value
* @return the least index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int indexOf(char[] array, char target) {
return indexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int indexOf(char[] array, char target, int start, int end) {
for (int i = start; i < end; i++) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the start position of the first occurrence of the specified {@code target} within
* {@code array}, or {@code -1} if there is no such occurrence.
*
* <p>More formally, returns the lowest index {@code i} such that {@code Arrays.copyOfRange(array,
* i, i + target.length)} contains exactly the same elements as {@code target}.
*
* @param array the array to search for the sequence {@code target}
* @param target the array to search for as a sub-sequence of {@code array}
*/
public static int indexOf(char[] array, char[] target) {
checkNotNull(array, "array");
checkNotNull(target, "target");
if (target.length == 0) {
return 0;
}
outer:
for (int i = 0; i < array.length - target.length + 1; i++) {
for (int j = 0; j < target.length; j++) {
if (array[i + j] != target[j]) {
continue outer;
}
}
return i;
}
return -1;
}
/**
* Returns the index of the last appearance of the value {@code target} in {@code array}.
*
* @param array an array of {@code char} values, possibly empty
* @param target a primitive {@code char} value
* @return the greatest index {@code i} for which {@code array[i] == target}, or {@code -1} if no
* such index exists.
*/
public static int lastIndexOf(char[] array, char target) {
return lastIndexOf(array, target, 0, array.length);
}
// TODO(kevinb): consider making this public
private static int lastIndexOf(char[] array, char target, int start, int end) {
for (int i = end - 1; i >= start; i--) {
if (array[i] == target) {
return i;
}
}
return -1;
}
/**
* Returns the least value present in {@code array}.
*
* @param array a <i>nonempty</i> array of {@code char} values
* @return the value present in {@code array} that is less than or equal to every other value in
* the array
* @throws IllegalArgumentException if {@code array} is empty
*/
public static char min(char... array) {
checkArgument(array.length > 0);
char min = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] < min) {
min = array[i];
}
}
return min;
}
/**
* Returns the greatest value present in {@code array}.
*
* @param array a <i>nonempty</i> array of {@code char} values
* @return the value present in {@code array} that is greater than or equal to every other value
* in the array
* @throws IllegalArgumentException if {@code array} is empty
*/
public static char max(char... array) {
checkArgument(array.length > 0);
char max = array[0];
for (int i = 1; i < array.length; i++) {
if (array[i] > max) {
max = array[i];
}
}
return max;
}
/**
* Returns the value nearest to {@code value} which is within the closed range {@code [min..max]}.
*
* <p>If {@code value} is within the range {@code [min..max]}, {@code value} is returned
* unchanged. If {@code value} is less than {@code min}, {@code min} is returned, and if {@code
* value} is greater than {@code max}, {@code max} is returned.
*
* @param value the {@code char} value to constrain
* @param min the lower bound (inclusive) of the range to constrain {@code value} to
* @param max the upper bound (inclusive) of the range to constrain {@code value} to
* @throws IllegalArgumentException if {@code min > max}
* @since 21.0
*/
@Beta
public static char constrainToRange(char value, char min, char max) {
checkArgument(min <= max, "min (%s) must be less than or equal to max (%s)", min, max);
return value < min ? min : value < max ? value : max;
}
/**
* Returns the values from each provided array combined into a single array. For example, {@code
* concat(new char[] {a, b}, new char[] {}, new char[] {c}} returns the array {@code {a, b, c}}.
*
* @param arrays zero or more {@code char} arrays
* @return a single array containing all the values from the source arrays, in order
*/
public static char[] concat(char[]... arrays) {
int length = 0;
for (char[] array : arrays) {
length += array.length;
}
char[] result = new char[length];
int pos = 0;
for (char[] array : arrays) {
System.arraycopy(array, 0, result, pos, array.length);
pos += array.length;
}
return result;
}
/**
* Returns a big-endian representation of {@code value} in a 2-element byte array; equivalent to
* {@code ByteBuffer.allocate(2).putChar(value).array()}. For example, the input value {@code
* '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
*
* <p>If you need to convert and concatenate several values (possibly even of different types),
* use a shared {@link java.nio.ByteBuffer} instance, or use {@link
* com.google.common.io.ByteStreams#newDataOutput()} to get a growable buffer.
*/
@GwtIncompatible // doesn't work
public static byte[] toByteArray(char value) {
return new byte[] {(byte) (value >> 8), (byte) value};
}
/**
* Returns the {@code char} value whose big-endian representation is stored in the first 2 bytes
* of {@code bytes}; equivalent to {@code ByteBuffer.wrap(bytes).getChar()}. For example, the
* input byte array {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
*
* <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that library exposes much more
* flexibility at little cost in readability.
*
* @throws IllegalArgumentException if {@code bytes} has fewer than 2 elements
*/
@GwtIncompatible // doesn't work
public static char fromByteArray(byte[] bytes) {
checkArgument(bytes.length >= BYTES, "array too small: %s < %s", bytes.length, BYTES);
return fromBytes(bytes[0], bytes[1]);
}
/**
* Returns the {@code char} value whose byte representation is the given 2 bytes, in big-endian
* order; equivalent to {@code Chars.fromByteArray(new byte[] {b1, b2})}.
*
* @since 7.0
*/
@GwtIncompatible // doesn't work
public static char fromBytes(byte b1, byte b2) {
return (char) ((b1 << 8) | (b2 & 0xFF));
}
/**
* Returns an array containing the same values as {@code array}, but guaranteed to be of a
* specified minimum length. If {@code array} already has a length of at least {@code minLength},
* it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
* returned, containing the values of {@code array}, and zeroes in the remaining places.
*
* @param array the source array
* @param minLength the minimum length the returned array must guarantee
* @param padding an extra amount to "grow" the array by if growth is necessary
* @throws IllegalArgumentException if {@code minLength} or {@code padding} is negative
* @return an array containing the values of {@code array}, with guaranteed minimum length {@code
* minLength}
*/
public static char[] ensureCapacity(char[] array, int minLength, int padding) {
checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
checkArgument(padding >= 0, "Invalid padding: %s", padding);
return (array.length < minLength) ? Arrays.copyOf(array, minLength + padding) : array;
}
/**
* Returns a string containing the supplied {@code char} values separated by {@code separator}.
* For example, {@code join("-", '1', '2', '3')} returns the string {@code "1-2-3"}.
*
* @param separator the text that should appear between consecutive values in the resulting string
* (but not at the start or end)
* @param array an array of {@code char} values, possibly empty
*/
public static String join(String separator, char... array) {
checkNotNull(separator);
int len = array.length;
if (len == 0) {
return "";
}
StringBuilder builder = new StringBuilder(len + separator.length() * (len - 1));
builder.append(array[0]);
for (int i = 1; i < len; i++) {
builder.append(separator).append(array[i]);
}
return builder.toString();
}
/**
* Returns a comparator that compares two {@code char} arrays <a
* href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>; not advisable
* for sorting user-visible strings as the ordering may not match the conventions of the user's
* locale. That is, it compares, using {@link #compare(char, char)}), the first pair of values
* that follow any common prefix, or when one array is a prefix of the other, treats the shorter
* array as the lesser. For example, {@code [] < ['a'] < ['a', 'b'] < ['b']}.
*
* <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
* support only identity equality), but it is consistent with {@link Arrays#equals(char[],
* char[])}.
*
* @since 2.0
*/
public static Comparator<char[]> lexicographicalComparator() {
return LexicographicalComparator.INSTANCE;
}
private enum LexicographicalComparator implements Comparator<char[]> {
INSTANCE;
@Override
public int compare(char[] left, char[] right) {
int minLength = Math.min(left.length, right.length);
for (int i = 0; i < minLength; i++) {
int result = Chars.compare(left[i], right[i]);
if (result != 0) {
return result;
}
}
return left.length - right.length;
}
@Override
public String toString() {
return "Chars.lexicographicalComparator()";
}
}
/**
* Copies a collection of {@code Character} instances into a new array of primitive {@code char}
* values.
*
* <p>Elements are copied from the argument collection as if by {@code collection.toArray()}.
* Calling this method is as thread-safe as calling that method.
*
* @param collection a collection of {@code Character} objects
* @return an array containing the same values as {@code collection}, in the same order, converted
* to primitives
* @throws NullPointerException if {@code collection} or any of its elements is null
*/
public static char[] toArray(Collection<Character> collection) {
if (collection instanceof CharArrayAsList) {
return ((CharArrayAsList) collection).toCharArray();
}
Object[] boxedArray = collection.toArray();
int len = boxedArray.length;
char[] array = new char[len];
for (int i = 0; i < len; i++) {
// checkNotNull for GWT (do not optimize)
array[i] = (Character) checkNotNull(boxedArray[i]);
}
return array;
}
/**
* Sorts the elements of {@code array} in descending order.
*
* @since 23.1
*/
public static void sortDescending(char[] array) {
checkNotNull(array);
sortDescending(array, 0, array.length);
}
/**
* Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
* exclusive in descending order.
*
* @since 23.1
*/
public static void sortDescending(char[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
Arrays.sort(array, fromIndex, toIndex);
reverse(array, fromIndex, toIndex);
}
/**
* Reverses the elements of {@code array}. This is equivalent to {@code
* Collections.reverse(Chars.asList(array))}, but is likely to be more efficient.
*
* @since 23.1
*/
public static void reverse(char[] array) {
checkNotNull(array);
reverse(array, 0, array.length);
}
/**
* Reverses the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
* exclusive. This is equivalent to {@code
* Collections.reverse(Chars.asList(array).subList(fromIndex, toIndex))}, but is likely to be more
* efficient.
*
* @throws IndexOutOfBoundsException if {@code fromIndex < 0}, {@code toIndex > array.length}, or
* {@code toIndex > fromIndex}
* @since 23.1
*/
public static void reverse(char[] array, int fromIndex, int toIndex) {
checkNotNull(array);
checkPositionIndexes(fromIndex, toIndex, array.length);
for (int i = fromIndex, j = toIndex - 1; i < j; i++, j--) {
char tmp = array[i];
array[i] = array[j];
array[j] = tmp;
}
}
/**
* Returns a fixed-size list backed by the specified array, similar to {@link
* Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)}, but any attempt to
* set a value to {@code null} will result in a {@link NullPointerException}.
*
* <p>The returned list maintains the values, but not the identities, of {@code Character} objects
* written to or read from it. For example, whether {@code list.get(0) == list.get(0)} is true for
* the returned list is unspecified.
*
* @param backingArray the array to back the list
* @return a list view of the array
*/
public static List<Character> asList(char... backingArray) {
if (backingArray.length == 0) {
return Collections.emptyList();
}
return new CharArrayAsList(backingArray);
}
@GwtCompatible
private static class CharArrayAsList extends AbstractList<Character>
implements RandomAccess, Serializable {
final char[] array;
final int start;
final int end;
CharArrayAsList(char[] array) {
this(array, 0, array.length);
}
CharArrayAsList(char[] array, int start, int end) {
this.array = array;
this.start = start;
this.end = end;
}
@Override
public int size() {
return end - start;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public Character get(int index) {
checkElementIndex(index, size());
return array[start + index];
}
@Override
public boolean contains(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
return (target instanceof Character)
&& Chars.indexOf(array, (Character) target, start, end) != -1;
}
@Override
public int indexOf(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Character) {
int i = Chars.indexOf(array, (Character) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public int lastIndexOf(@CheckForNull Object target) {
// Overridden to prevent a ton of boxing
if (target instanceof Character) {
int i = Chars.lastIndexOf(array, (Character) target, start, end);
if (i >= 0) {
return i - start;
}
}
return -1;
}
@Override
public Character set(int index, Character element) {
checkElementIndex(index, size());
char oldValue = array[start + index];
// checkNotNull for GWT (do not optimize)
array[start + index] = checkNotNull(element);
return oldValue;
}
@Override
public List<Character> subList(int fromIndex, int toIndex) {
int size = size();
checkPositionIndexes(fromIndex, toIndex, size);
if (fromIndex == toIndex) {
return Collections.emptyList();
}
return new CharArrayAsList(array, start + fromIndex, start + toIndex);
}
@Override
public boolean equals(@CheckForNull Object object) {
if (object == this) {
return true;
}
if (object instanceof CharArrayAsList) {
CharArrayAsList that = (CharArrayAsList) object;
int size = size();
if (that.size() != size) {
return false;
}
for (int i = 0; i < size; i++) {
if (array[start + i] != that.array[that.start + i]) {
return false;
}
}
return true;
}
return super.equals(object);
}
@Override
public int hashCode() {
int result = 1;
for (int i = start; i < end; i++) {
result = 31 * result + Chars.hashCode(array[i]);
}
return result;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(size() * 3);
builder.append('[').append(array[start]);
for (int i = start + 1; i < end; i++) {
builder.append(", ").append(array[i]);
}
return builder.append(']').toString();
}
char[] toCharArray() {
return Arrays.copyOfRange(array, start, end);
}
private static final long serialVersionUID = 0;
}
}