554 lines
17 KiB
Java
554 lines
17 KiB
Java
/*
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* Copyright (C) 2008 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.primitives;
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import static com.google.common.base.Preconditions.checkArgument;
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import static com.google.common.base.Preconditions.checkElementIndex;
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import static com.google.common.base.Preconditions.checkNotNull;
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import static com.google.common.base.Preconditions.checkPositionIndexes;
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import java.io.Serializable;
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import java.util.AbstractList;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.List;
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import java.util.RandomAccess;
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import com.google.common.annotations.GwtCompatible;
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/**
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* Static utility methods pertaining to {@code char} primitives, that are not
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* already found in either {@link Character} or {@link Arrays}.
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*
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* <p>
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* All the operations in this class treat {@code char} values strictly
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* numerically; they are neither Unicode-aware nor locale-dependent.
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*
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* <p>
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* See the Guava User Guide article on
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* <a href= "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
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* primitive utilities</a>.
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*
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* @author Kevin Bourrillion
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* @since 1.0
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*/
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@GwtCompatible(emulated = true)
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public final class Chars {
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private Chars() {
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}
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/**
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* The number of bytes required to represent a primitive {@code char} value.
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*/
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public static final int BYTES = Character.SIZE / Byte.SIZE;
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/**
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* Returns a hash code for {@code value}; equal to the result of invoking
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* {@code ((Character) value).hashCode()}.
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*
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* @param value a primitive {@code char} value
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* @return a hash code for the value
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*/
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public static int hashCode(char value) {
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return value;
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}
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/**
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* Returns the {@code char} value that is equal to {@code value}, if possible.
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*
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* @param value any value in the range of the {@code char} type
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* @return the {@code char} value that equals {@code value}
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* @throws IllegalArgumentException if {@code value} is greater than
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* {@link Character#MAX_VALUE} or less than
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* {@link Character#MIN_VALUE}
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*/
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public static char checkedCast(long value) {
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char result = (char) value;
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if (result != value) {
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// don't use checkArgument here, to avoid boxing
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throw new IllegalArgumentException("Out of range: " + value);
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}
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return result;
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}
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/**
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* Returns the {@code char} nearest in value to {@code value}.
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*
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* @param value any {@code long} value
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* @return the same value cast to {@code char} if it is in the range of the
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* {@code char} type, {@link Character#MAX_VALUE} if it is too large, or
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* {@link Character#MIN_VALUE} if it is too small
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*/
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public static char saturatedCast(long value) {
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if (value > Character.MAX_VALUE) {
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return Character.MAX_VALUE;
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}
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if (value < Character.MIN_VALUE) {
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return Character.MIN_VALUE;
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}
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return (char) value;
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}
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/**
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* Compares the two specified {@code char} values. The sign of the value
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* returned is the same as that of {@code ((Character) a).compareTo(b)}.
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*
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* <p>
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* <b>Note:</b> projects using JDK 7 or later should use the equivalent
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* {@link Character#compare} method instead.
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*
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* @param a the first {@code char} to compare
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* @param b the second {@code char} to compare
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* @return a negative value if {@code a} is less than {@code b}; a positive
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* value if {@code a} is greater than {@code b}; or zero if they are
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* equal
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*/
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public static int compare(char a, char b) {
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return a - b; // safe due to restricted range
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}
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/**
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* Returns {@code true} if {@code target} is present as an element anywhere in
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* {@code array}.
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*
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* @param array an array of {@code char} values, possibly empty
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* @param target a primitive {@code char} value
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* @return {@code true} if {@code array[i] == target} for some value of {@code
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* i}
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*/
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public static boolean contains(char[] array, char target) {
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for (char value : array) {
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if (value == target) {
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return true;
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}
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}
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return false;
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}
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/**
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* Returns the index of the first appearance of the value {@code target} in
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* {@code array}.
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*
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* @param array an array of {@code char} values, possibly empty
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* @param target a primitive {@code char} value
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* @return the least index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int indexOf(char[] array, char target) {
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return indexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int indexOf(char[] array, char target, int start, int end) {
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for (int i = start; i < end; i++) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the start position of the first occurrence of the specified {@code
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* target} within {@code array}, or {@code -1} if there is no such occurrence.
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*
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* <p>
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* More formally, returns the lowest index {@code i} such that {@code
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* java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
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* the same elements as {@code target}.
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*
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* @param array the array to search for the sequence {@code target}
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* @param target the array to search for as a sub-sequence of {@code array}
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*/
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public static int indexOf(char[] array, char[] target) {
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checkNotNull(array, "array");
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checkNotNull(target, "target");
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if (target.length == 0) {
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return 0;
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}
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outer: for (int i = 0; i < array.length - target.length + 1; i++) {
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for (int j = 0; j < target.length; j++) {
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if (array[i + j] != target[j]) {
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continue outer;
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}
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}
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return i;
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}
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return -1;
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}
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/**
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* Returns the index of the last appearance of the value {@code target} in
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* {@code array}.
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*
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* @param array an array of {@code char} values, possibly empty
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* @param target a primitive {@code char} value
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* @return the greatest index {@code i} for which {@code array[i] == target}, or
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* {@code -1} if no such index exists.
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*/
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public static int lastIndexOf(char[] array, char target) {
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return lastIndexOf(array, target, 0, array.length);
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}
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// TODO(kevinb): consider making this public
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private static int lastIndexOf(char[] array, char target, int start, int end) {
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for (int i = end - 1; i >= start; i--) {
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if (array[i] == target) {
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return i;
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}
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}
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return -1;
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}
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/**
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* Returns the least value present in {@code array}.
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*
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* @param array a <i>nonempty</i> array of {@code char} values
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* @return the value present in {@code array} that is less than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static char min(char... array) {
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checkArgument(array.length > 0);
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char min = array[0];
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for (int i = 1; i < array.length; i++) {
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if (array[i] < min) {
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min = array[i];
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}
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}
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return min;
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}
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/**
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* Returns the greatest value present in {@code array}.
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*
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* @param array a <i>nonempty</i> array of {@code char} values
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* @return the value present in {@code array} that is greater than or equal to
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* every other value in the array
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* @throws IllegalArgumentException if {@code array} is empty
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*/
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public static char max(char... array) {
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checkArgument(array.length > 0);
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char max = array[0];
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for (int i = 1; i < array.length; i++) {
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if (array[i] > max) {
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max = array[i];
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}
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}
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return max;
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}
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/**
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* Returns the values from each provided array combined into a single array. For
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* example, {@code concat(new char[] {a, b}, new char[] {}, new char[] {c}}
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* returns the array {@code {a, b, c}}.
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*
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* @param arrays zero or more {@code char} arrays
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* @return a single array containing all the values from the source arrays, in
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* order
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*/
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public static char[] concat(char[]... arrays) {
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int length = 0;
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for (char[] array : arrays) {
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length += array.length;
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}
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char[] result = new char[length];
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int pos = 0;
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for (char[] array : arrays) {
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System.arraycopy(array, 0, result, pos, array.length);
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pos += array.length;
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}
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return result;
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}
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/**
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* Returns an array containing the same values as {@code array}, but guaranteed
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* to be of a specified minimum length. If {@code array} already has a length of
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* at least {@code minLength}, it is returned directly. Otherwise, a new array
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* of size {@code minLength + padding} is returned, containing the values of
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* {@code array}, and zeroes in the remaining places.
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*
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* @param array the source array
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* @param minLength the minimum length the returned array must guarantee
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* @param padding an extra amount to "grow" the array by if growth is
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* necessary
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* @throws IllegalArgumentException if {@code minLength} or {@code padding} is
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* negative
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* @return an array containing the values of {@code array}, with guaranteed
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* minimum length {@code minLength}
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*/
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public static char[] ensureCapacity(char[] array, int minLength, int padding) {
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checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
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checkArgument(padding >= 0, "Invalid padding: %s", padding);
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return (array.length < minLength) ? copyOf(array, minLength + padding) : array;
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}
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// Arrays.copyOf() requires Java 6
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private static char[] copyOf(char[] original, int length) {
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char[] copy = new char[length];
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System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
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return copy;
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}
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/**
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* Returns a string containing the supplied {@code char} values separated by
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* {@code separator}. For example, {@code join("-", '1', '2', '3')} returns the
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* string {@code "1-2-3"}.
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*
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* @param separator the text that should appear between consecutive values in
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* the resulting string (but not at the start or end)
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* @param array an array of {@code char} values, possibly empty
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*/
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public static String join(String separator, char... array) {
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checkNotNull(separator);
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int len = array.length;
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if (len == 0) {
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return "";
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}
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StringBuilder builder = new StringBuilder(len + separator.length() * (len - 1));
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builder.append(array[0]);
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for (int i = 1; i < len; i++) {
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builder.append(separator).append(array[i]);
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}
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return builder.toString();
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}
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/**
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* Returns a comparator that compares two {@code char} arrays lexicographically.
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* That is, it compares, using {@link #compare(char, char)}), the first pair of
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* values that follow any common prefix, or when one array is a prefix of the
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* other, treats the shorter array as the lesser. For example,
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* {@code [] < ['a'] < ['a', 'b'] < ['b']}.
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*
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* <p>
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* The returned comparator is inconsistent with {@link Object#equals(Object)}
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* (since arrays support only identity equality), but it is consistent with
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* {@link Arrays#equals(char[], char[])}.
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*
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* @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
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* Lexicographical order article at Wikipedia</a>
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* @since 2.0
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*/
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public static Comparator<char[]> lexicographicalComparator() {
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return LexicographicalComparator.INSTANCE;
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}
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private enum LexicographicalComparator implements Comparator<char[]> {
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INSTANCE;
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@Override
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public int compare(char[] left, char[] right) {
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int minLength = Math.min(left.length, right.length);
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for (int i = 0; i < minLength; i++) {
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int result = Chars.compare(left[i], right[i]);
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if (result != 0) {
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return result;
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}
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}
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return left.length - right.length;
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}
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}
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/**
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* Copies a collection of {@code Character} instances into a new array of
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* primitive {@code char} values.
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*
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* <p>
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* Elements are copied from the argument collection as if by {@code
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* collection.toArray()}. Calling this method is as thread-safe as calling that
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* method.
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*
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* @param collection a collection of {@code Character} objects
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* @return an array containing the same values as {@code collection}, in the
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* same order, converted to primitives
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* @throws NullPointerException if {@code collection} or any of its elements is
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* null
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*/
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public static char[] toArray(Collection<Character> collection) {
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if (collection instanceof CharArrayAsList) {
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return ((CharArrayAsList) collection).toCharArray();
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}
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Object[] boxedArray = collection.toArray();
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int len = boxedArray.length;
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char[] array = new char[len];
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for (int i = 0; i < len; i++) {
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// checkNotNull for GWT (do not optimize)
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array[i] = (Character) checkNotNull(boxedArray[i]);
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}
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return array;
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}
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/**
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* Returns a fixed-size list backed by the specified array, similar to
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* {@link Arrays#asList(Object[])}. The list supports
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* {@link List#set(int, Object)}, but any attempt to set a value to {@code null}
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* will result in a {@link NullPointerException}.
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*
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* <p>
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* The returned list maintains the values, but not the identities, of
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* {@code Character} objects written to or read from it. For example, whether
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* {@code list.get(0) == list.get(0)} is true for the returned list is
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* unspecified.
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*
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* @param backingArray the array to back the list
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* @return a list view of the array
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*/
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public static List<Character> asList(char... backingArray) {
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if (backingArray.length == 0) {
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return Collections.emptyList();
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}
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return new CharArrayAsList(backingArray);
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}
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@GwtCompatible
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private static class CharArrayAsList extends AbstractList<Character> implements RandomAccess, Serializable {
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final char[] array;
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final int start;
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final int end;
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CharArrayAsList(char[] array) {
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this(array, 0, array.length);
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}
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CharArrayAsList(char[] array, int start, int end) {
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this.array = array;
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this.start = start;
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this.end = end;
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}
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@Override
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public int size() {
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return end - start;
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}
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@Override
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public boolean isEmpty() {
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return false;
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}
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@Override
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public Character get(int index) {
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checkElementIndex(index, size());
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return array[start + index];
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}
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@Override
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public boolean contains(Object target) {
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// Overridden to prevent a ton of boxing
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return (target instanceof Character) && Chars.indexOf(array, (Character) target, start, end) != -1;
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}
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@Override
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public int indexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Character) {
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int i = Chars.indexOf(array, (Character) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public int lastIndexOf(Object target) {
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// Overridden to prevent a ton of boxing
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if (target instanceof Character) {
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int i = Chars.lastIndexOf(array, (Character) target, start, end);
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if (i >= 0) {
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return i - start;
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}
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}
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return -1;
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}
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@Override
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public Character set(int index, Character element) {
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checkElementIndex(index, size());
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char oldValue = array[start + index];
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// checkNotNull for GWT (do not optimize)
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array[start + index] = checkNotNull(element);
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return oldValue;
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}
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@Override
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public List<Character> subList(int fromIndex, int toIndex) {
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int size = size();
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checkPositionIndexes(fromIndex, toIndex, size);
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if (fromIndex == toIndex) {
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return Collections.emptyList();
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}
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return new CharArrayAsList(array, start + fromIndex, start + toIndex);
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}
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@Override
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public boolean equals(Object object) {
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if (object == this) {
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return true;
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}
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if (object instanceof CharArrayAsList) {
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CharArrayAsList that = (CharArrayAsList) object;
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int size = size();
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if (that.size() != size) {
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return false;
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}
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for (int i = 0; i < size; i++) {
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if (array[start + i] != that.array[that.start + i]) {
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return false;
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}
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}
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return true;
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}
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return super.equals(object);
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}
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@Override
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public int hashCode() {
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int result = 1;
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for (int i = start; i < end; i++) {
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result = 31 * result + Chars.hashCode(array[i]);
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}
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return result;
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}
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@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() {
|
|
// Arrays.copyOfRange() is not available under GWT
|
|
int size = size();
|
|
char[] result = new char[size];
|
|
System.arraycopy(array, start, result, 0, size);
|
|
return result;
|
|
}
|
|
|
|
private static final long serialVersionUID = 0;
|
|
}
|
|
}
|