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.functor.core;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.BinaryProcedure;
22 import org.apache.commons.functor.Procedure;
23 import org.apache.commons.functor.UnaryProcedure;
24
25 /**
26 * A procedure that does nothing at all.
27 * <p>
28 * Note that this class implements {@link Procedure},
29 * {@link UnaryProcedure}, and {@link BinaryProcedure}.
30 * </p>
31 * @version $Revision: 1156349 $ $Date: 2011-08-10 22:21:14 +0200 (Wed, 10 Aug 2011) $
32 * @author Rodney Waldhoff
33 */
34 public final class NoOp implements Procedure, UnaryProcedure<Object>, BinaryProcedure<Object, Object>, Serializable {
35 // static attributes
36 // ------------------------------------------------------------------------
37 /**
38 * Basic NoOp instance.
39 */
40 public static final NoOp INSTANCE = new NoOp();
41 /**
42 * serialVersionUID declaration.
43 */
44 private static final long serialVersionUID = 3768926349922273291L;
45
46 // constructor
47 // ------------------------------------------------------------------------
48 /**
49 * Create a new NoOp.
50 */
51 public NoOp() {
52 }
53
54 // predicate interface
55 // ------------------------------------------------------------------------
56 /**
57 * {@inheritDoc}
58 */
59 public void run() {
60 }
61
62 /**
63 * {@inheritDoc}
64 */
65 public void run(Object obj) {
66 }
67
68 /**
69 * {@inheritDoc}
70 */
71 public void run(Object left, Object right) {
72 }
73
74 /**
75 * {@inheritDoc}
76 */
77 public boolean equals(Object that) {
78 return (that instanceof NoOp);
79 }
80
81 /**
82 * {@inheritDoc}
83 */
84 public int hashCode() {
85 return "NoOp".hashCode();
86 }
87
88 /**
89 * {@inheritDoc}
90 */
91 public String toString() {
92 return "NoOp";
93 }
94
95 // static methods
96 // ------------------------------------------------------------------------
97 /**
98 * Get a NoOp instance.
99 * @return NoOp
100 */
101 public static NoOp instance() {
102 return INSTANCE;
103 }
104
105 /**
106 * Get a typed NoOp {@link UnaryProcedure}.
107 * @param <A> type
108 * @return <code>UnaryProcedure<A></code>
109 */
110 @SuppressWarnings("unchecked")
111 public static <A> UnaryProcedure<A> unaryInstance() {
112 return (UnaryProcedure<A>) INSTANCE;
113 }
114
115 /**
116 * Get a typed NoOp {@link BinaryProcedure}.
117 * @param <L> left type
118 * @param <R> right type
119 * @return <code>BinaryProcedure<L, R></code>
120 */
121 @SuppressWarnings("unchecked")
122 public static <L, R> BinaryProcedure<L, R> binaryInstance() {
123 return (BinaryProcedure<L, R>) INSTANCE;
124 }
125 }