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  import java.util.HashSet;
23  
24  /**
25   * Translates a value using a lookup table.
26   *
27   * @since 3.0
28   */
29  public class LookupTranslator extends CharSequenceTranslator {
30  
31      private final HashMap<String, String> lookupMap;
32      private final HashSet<Character> prefixSet;
33      private final int shortest;
34      private final int longest;
35  
36      /**
37       * Define the lookup table to be used in translation
38       *
39       * Note that, as of Lang 3.1, the key to the lookup table is converted to a
40       * java.lang.String. This is because we need the key to support hashCode and
41       * equals(Object), 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, String>();
47          prefixSet = new HashSet<Character>();
48          int _shortest = Integer.MAX_VALUE;
49          int _longest = 0;
50          if (lookup != null) {
51              for (final CharSequence[] seq : lookup) {
52                  this.lookupMap.put(seq[0].toString(), seq[1].toString());
53                  this.prefixSet.add(seq[0].charAt(0));
54                  final int sz = seq[0].length();
55                  if (sz < _shortest) {
56                      _shortest = sz;
57                  }
58                  if (sz > _longest) {
59                      _longest = sz;
60                  }
61              }
62          }
63          shortest = _shortest;
64          longest = _longest;
65      }
66  
67      /**
68       * {@inheritDoc}
69       */
70      @Override
71      public int translate(final CharSequence input, final int index, final Writer out) throws IOException {
72          // check if translation exists for the input at position index
73          if (prefixSet.contains(input.charAt(index))) {
74              int max = longest;
75              if (index + longest > input.length()) {
76                  max = input.length() - index;
77              }
78              // implement greedy algorithm by trying maximum match first
79              for (int i = max; i >= shortest; i--) {
80                  final CharSequence subSeq = input.subSequence(index, index + i);
81                  final String result = lookupMap.get(subSeq.toString());
82  
83                  if (result != null) {
84                      out.write(result);
85                      return i;
86                  }
87              }
88          }
89          return 0;
90      }
91  }