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.collections.functors;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.collections.Closure;
22
23 /**
24 * Closure implementation that does nothing.
25 *
26 * @since 3.0
27 * @version $Id: NOPClosure.java 1429905 2013-01-07 17:15:14Z ggregory $
28 */
29 public final class NOPClosure<E> implements Closure<E>, Serializable {
30
31 /** Serial version UID */
32 private static final long serialVersionUID = 3518477308466486130L;
33
34 /** Singleton predicate instance */
35 public static final Closure<Object> INSTANCE = new NOPClosure<Object>();
36
37 /**
38 * Factory returning the singleton instance.
39 *
40 * @param <E> the type that the closure acts on
41 * @return the singleton instance
42 * @since 3.1
43 */
44 @SuppressWarnings("unchecked")
45 public static <E> Closure<E> nopClosure() {
46 return (Closure<E>) INSTANCE;
47 }
48
49 /**
50 * Constructor
51 */
52 private NOPClosure() {
53 super();
54 }
55
56 /**
57 * Do nothing.
58 *
59 * @param input the input object
60 */
61 public void execute(final E input) {
62 // do nothing
63 }
64
65 private Object readResolve() {
66 return INSTANCE;
67 }
68
69 }