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.adapter;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.Function;
22 import org.apache.commons.functor.Procedure;
23 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link Procedure Procedure}
28 * to the
29 * {@link Function Function} interface
30 * by always returning <code>null</code>.
31 * <p/>
32 * Note that although this class implements
33 * {@link Serializable}, a given instance will
34 * only be truly <code>Serializable</code> if the
35 * underlying procedure is. Attempts to serialize
36 * an instance whose delegate is not
37 * <code>Serializable</code> will result in an exception.
38 *
39 * @param <T> the returned value type.
40 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
41 */
42 public final class ProcedureFunction<T> implements Function<T>, Serializable {
43 /**
44 * serialVersionUID declaration.
45 */
46 private static final long serialVersionUID = -655207616317672341L;
47 /** The {@link Procedure Procedure} I'm wrapping. */
48 private final Procedure procedure;
49
50 /**
51 * Create a new ProcedureFunction.
52 * @param procedure to adapt
53 */
54 public ProcedureFunction(Procedure procedure) {
55 this.procedure = Validate.notNull(procedure, "Procedure argument was null");
56 }
57
58 /**
59 * {@inheritDoc}
60 */
61 public T evaluate() {
62 procedure.run();
63 return null;
64 }
65
66 /**
67 * {@inheritDoc}
68 */
69 @Override
70 public boolean equals(Object that) {
71 return that == this || (that instanceof ProcedureFunction<?> && equals((ProcedureFunction<?>) that));
72 }
73
74 /**
75 * Learn whether another ProcedureFunction is equal to this.
76 * @param that ProcedureFunction to test
77 * @return boolean
78 */
79 public boolean equals(ProcedureFunction<?> that) {
80 return null != that && procedure.equals(that.procedure);
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 @Override
87 public int hashCode() {
88 int hash = "ProcedureFunction".hashCode();
89 hash ^= procedure.hashCode();
90 return hash;
91 }
92
93 /**
94 * {@inheritDoc}
95 */
96 @Override
97 public String toString() {
98 return "ProcedureFunction<" + procedure + ">";
99 }
100
101 /**
102 * Adapt a Procedure as a Function.
103 * @param <T> the returned value type.
104 * @param procedure to adapt
105 * @return ProcedureFunction<T>
106 */
107 public static <T> ProcedureFunction<T> adapt(Procedure procedure) {
108 return null == procedure ? null : new ProcedureFunction<T>(procedure);
109 }
110
111 }