View Javadoc
1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.lang3.text.translate;
18  
19  import java.io.IOException;
20  import java.io.Writer;
21  import java.util.HashMap;
22  
23  /**
24   * Translates a value using a lookup table.
25   *
26   * @since 3.0
27   * @version $Id: LookupTranslator.java 1470822 2013-04-23 06:00:41Z bayard $
28   */
29  public class LookupTranslator extends CharSequenceTranslator {
30  
31      private final HashMap<String, CharSequence> lookupMap;
32      private final int shortest;
33      private final int longest;
34  
35      /**
36       * Define the lookup table to be used in translation
37       *
38       * Note that, as of Lang 3.1, the key to the lookup table is converted to a 
39       * java.lang.String, while the value remains as a java.lang.CharSequence. 
40       * This is because we need the key to support hashCode and equals(Object), 
41       * allowing it to be the key for a HashMap. See LANG-882.
42       *
43       * @param lookup CharSequence[][] table of size [*][2]
44       */
45      public LookupTranslator(final CharSequence[]... lookup) {
46          lookupMap = new HashMap<String, CharSequence>();
47          int _shortest = Integer.MAX_VALUE;
48          int _longest = 0;
49          if (lookup != null) {
50              for (final CharSequence[] seq : lookup) {
51                  this.lookupMap.put(seq[0].toString(), seq[1]);
52                  final int sz = seq[0].length();
53                  if (sz < _shortest) {
54                      _shortest = sz;
55                  }
56                  if (sz > _longest) {
57                      _longest = sz;
58                  }
59              }
60          }
61          shortest = _shortest;
62          longest = _longest;
63      }
64  
65      /**
66       * {@inheritDoc}
67       */
68      @Override
69      public int translate(final CharSequence input, final int index, final Writer out) throws IOException {
70          int max = longest;
71          if (index + longest > input.length()) {
72              max = input.length() - index;
73          }
74          // descend so as to get a greedy algorithm
75          for (int i = max; i >= shortest; i--) {
76              final CharSequence subSeq = input.subSequence(index, index + i);
77              final CharSequence result = lookupMap.get(subSeq.toString());
78              if (result != null) {
79                  out.write(result.toString());
80                  return i;
81              }
82          }
83          return 0;
84      }
85  }