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
21 import org.apache.commons.collections4.Transformer;
22
23 /**
24 * Transformer implementation that does nothing.
25 *
26 * @param <T> the type of the input and result to the function.
27 * @since 3.0
28 */
29 public class NOPTransformer<T> implements Transformer<T, T>, Serializable {
30
31 /** Serial version UID */
32 private static final long serialVersionUID = 2133891748318574490L;
33
34 /** Singleton predicate instance */
35 @SuppressWarnings("rawtypes")
36 public static final Transformer INSTANCE = new NOPTransformer<>();
37
38 /**
39 * Factory returning the singleton instance.
40 *
41 * @param <T> the input/output type
42 * @return the singleton instance
43 * @since 3.1
44 */
45 public static <T> Transformer<T, T> nopTransformer() {
46 return INSTANCE;
47 }
48
49 /**
50 * Constructs a new instance.
51 */
52 private NOPTransformer() {
53 }
54
55 /**
56 * Returns the singleton instance.
57 *
58 * @return the singleton instance.
59 */
60 private Object readResolve() {
61 return INSTANCE;
62 }
63
64 /**
65 * Transforms the input to result by doing nothing.
66 *
67 * @param input the input object to transform
68 * @return the transformed result which is the input
69 */
70 @Override
71 public T transform(final T input) {
72 return input;
73 }
74
75 }