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Java example source code file (

This example Java source code file ( is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

charsequence, charsequencetranslator, hashmap, hashset, ioexception, lookuptranslator, override, string, util, writer

The Java example source code

 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.lang3.text.translate;

import java.util.HashMap;
import java.util.HashSet;

 * Translates a value using a lookup table.
 * @since 3.0
public class LookupTranslator extends CharSequenceTranslator {

    private final HashMap<String, String> lookupMap;
    private final HashSet<Character> prefixSet;
    private final int shortest;
    private final int longest;

     * Define the lookup table to be used in translation
     * Note that, as of Lang 3.1, the key to the lookup table is converted to a
     * java.lang.String. This is because we need the key to support hashCode and
     * equals(Object), allowing it to be the key for a HashMap. See LANG-882.
     * @param lookup CharSequence[][] table of size [*][2]
    public LookupTranslator(final CharSequence[]... lookup) {
        lookupMap = new HashMap<String, String>();
        prefixSet = new HashSet<Character>();
        int _shortest = Integer.MAX_VALUE;
        int _longest = 0;
        if (lookup != null) {
            for (final CharSequence[] seq : lookup) {
                this.lookupMap.put(seq[0].toString(), seq[1].toString());
                final int sz = seq[0].length();
                if (sz < _shortest) {
                    _shortest = sz;
                if (sz > _longest) {
                    _longest = sz;
        shortest = _shortest;
        longest = _longest;

     * {@inheritDoc}
    public int translate(final CharSequence input, final int index, final Writer out) throws IOException {
        // check if translation exists for the input at position index
        if (prefixSet.contains(input.charAt(index))) {
            int max = longest;
            if (index + longest > input.length()) {
                max = input.length() - index;
            // implement greedy algorithm by trying maximum match first
            for (int i = max; i >= shortest; i--) {
                final CharSequence subSeq = input.subSequence(index, index + i);
                final String result = lookupMap.get(subSeq.toString());

                if (result != null) {
                    return i;
        return 0;

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