001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.text.translate; 018 019import java.io.IOException; 020import java.io.Writer; 021import java.security.InvalidParameterException; 022import java.util.HashMap; 023import java.util.HashSet; 024import java.util.Iterator; 025import java.util.Map; 026 027/** 028 * Translates a value using a lookup table. 029 * 030 * @since 1.0 031 */ 032public class LookupTranslator extends CharSequenceTranslator { 033 034 /** The mapping to be used in translation. */ 035 private final Map<String, String> lookupMap; 036 /** The first character of each key in the lookupMap. */ 037 private final HashSet<Character> prefixSet; 038 /** The length of the shortest key in the lookupMap. */ 039 private final int shortest; 040 /** The length of the longest key in the lookupMap. */ 041 private final int longest; 042 043 /** 044 * Define the lookup table to be used in translation 045 * 046 * Note that, as of Lang 3.1 (the orgin of this code), the key to the lookup 047 * table is converted to a java.lang.String. This is because we need the key 048 * to support hashCode and equals(Object), allowing it to be the key for a 049 * HashMap. See LANG-882. 050 * 051 * @param lookupMap Map<CharSequence, CharSequence> table of translator 052 * mappings 053 */ 054 public LookupTranslator(final Map<CharSequence, CharSequence> lookupMap) { 055 if (lookupMap == null) { 056 throw new InvalidParameterException("lookupMap cannot be null"); 057 } 058 this.lookupMap = new HashMap<>(); 059 this.prefixSet = new HashSet<>(); 060 int currentShortest = Integer.MAX_VALUE; 061 int currentLongest = 0; 062 Iterator<Map.Entry<CharSequence, CharSequence>> it = lookupMap.entrySet().iterator(); 063 064 while (it.hasNext()) { 065 Map.Entry<CharSequence, CharSequence> pair = it.next(); 066 this.lookupMap.put(pair.getKey().toString(), pair.getValue().toString()); 067 this.prefixSet.add(pair.getKey().charAt(0)); 068 final int sz = pair.getKey().length(); 069 if (sz < currentShortest) { 070 currentShortest = sz; 071 } 072 if (sz > currentLongest) { 073 currentLongest = sz; 074 } 075 } 076 this.shortest = currentShortest; 077 this.longest = currentLongest; 078 } 079 080 /** 081 * {@inheritDoc} 082 */ 083 @Override 084 public int translate(final CharSequence input, final int index, final Writer out) throws IOException { 085 // check if translation exists for the input at position index 086 if (prefixSet.contains(input.charAt(index))) { 087 int max = longest; 088 if (index + longest > input.length()) { 089 max = input.length() - index; 090 } 091 // implement greedy algorithm by trying maximum match first 092 for (int i = max; i >= shortest; i--) { 093 final CharSequence subSeq = input.subSequence(index, index + i); 094 final String result = lookupMap.get(subSeq.toString()); 095 096 if (result != null) { 097 out.write(result); 098 return i; 099 } 100 } 101 } 102 return 0; 103 } 104}