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.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       * Constructor.
50       */
51      private NOPTransformer() {
52          super();
53      }
54  
55      /**
56       * Transforms the input to result by doing nothing.
57       *
58       * @param input  the input object to transform
59       * @return the transformed result which is the input
60       */
61      @Override
62      public T transform(final T input) {
63          return input;
64      }
65  
66      private Object readResolve() {
67          return INSTANCE;
68      }
69  
70  }