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Java > Open Source Codes > org > apache > commons > collections > functors > MapTransformer


1 /*
2  * Copyright 2001-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.collections.functors;
17
18 import java.io.Serializable JavaDoc;
19 import java.util.Map JavaDoc;
20
21 import org.apache.commons.collections.Transformer;
22
23 /**
24  * Transformer implementation that returns the value held in a specified map
25  * using the input parameter as a key.
26  *
27  * @since Commons Collections 3.0
28  * @version $Revision: 1.7 $ $Date: 2004/05/16 11:36:31 $
29  *
30  * @author Stephen Colebourne
31  */
32 public final class MapTransformer implements Transformer, Serializable JavaDoc {
33
34     /** Serial version UID */
35     static final long serialVersionUID = 862391807045468939L;
36     
37     /** The map of data to lookup in */
38     private final Map JavaDoc iMap;
39
40     /**
41      * Factory to create the transformer.
42      * <p>
43      * If the map is null, a transformer that always returns null is returned.
44      *
45      * @param map the map, not cloned
46      * @return the transformer
47      */
48     public static Transformer getInstance(Map JavaDoc map) {
49         if (map == null) {
50             return ConstantTransformer.NULL_INSTANCE;
51         }
52         return new MapTransformer(map);
53     }
54
55     /**
56      * Constructor that performs no validation.
57      * Use <code>getInstance</code> if you want that.
58      *
59      * @param map the map to use for lookup, not cloned
60      */
61     private MapTransformer(Map JavaDoc map) {
62         super();
63         iMap = map;
64     }
65
66     /**
67      * Transforms the input to result by looking it up in a <code>Map</code>.
68      *
69      * @param input the input object to transform
70      * @return the transformed result
71      */
72     public Object JavaDoc transform(Object JavaDoc input) {
73         return iMap.get(input);
74     }
75
76     /**
77      * Gets the map to lookup in.
78      *
79      * @return the map
80      * @since Commons Collections 3.1
81      */
82     public Map JavaDoc getMap() {
83         return iMap;
84     }
85
86 }
87
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