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