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.collections4.functors;
18
19 import java.io.Serializable;
20 import java.util.Map;
21
22 import org.apache.commons.collections4.Transformer;
23
24 /**
25 * Transformer implementation that returns the value held in a specified map
26 * using the input parameter as a key.
27 *
28 * @since 3.0
29 */
30 public final class MapTransformer<I, O> implements Transformer<I, O>, Serializable {
31
32 /** Serial version UID */
33 private static final long serialVersionUID = 862391807045468939L;
34
35 /**
36 * Factory to create the transformer.
37 * <p>
38 * If the map is null, a transformer that always returns null is returned.
39 *
40 * @param <I> the input type
41 * @param <O> the output type
42 * @param map the map, not cloned
43 * @return the transformer
44 */
45 public static <I, O> Transformer<I, O> mapTransformer(final Map<? super I, ? extends O> map) {
46 if (map == null) {
47 return ConstantTransformer.<I, O>nullTransformer();
48 }
49 return new MapTransformer<>(map);
50 }
51
52 /** The map of data to lookup in */
53 private final Map<? super I, ? extends O> iMap;
54
55 /**
56 * Constructor that performs no validation.
57 * Use {@code mapTransformer} if you want that.
58 *
59 * @param map the map to use for lookup, not cloned
60 */
61 private MapTransformer(final Map<? super I, ? extends O> map) {
62 iMap = map;
63 }
64
65 /**
66 * Gets the map to lookup in.
67 *
68 * @return the map
69 * @since 3.1
70 */
71 public Map<? super I, ? extends O> getMap() {
72 return iMap;
73 }
74
75 /**
76 * Transforms the input to result by looking it up in a {@code Map}.
77 *
78 * @param input the input object to transform
79 * @return the transformed result
80 */
81 @Override
82 public O transform(final I input) {
83 return iMap.get(input);
84 }
85
86 }