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
24 /**
25 * Adapts a
26 * {@link Procedure Procedure}
27 * to the
28 * {@link Function Function} interface
29 * by always returning <code>null</code>.
30 * <p/>
31 * Note that although this class implements
32 * {@link Serializable}, a given instance will
33 * only be truly <code>Serializable</code> if the
34 * underlying procedure is. Attempts to serialize
35 * an instance whose delegate is not
36 * <code>Serializable</code> will result in an exception.
37 *
38 * @param <T> the returned value type.
39 * @version $Revision: 1157630 $ $Date: 2011-08-14 22:06:30 +0200 (Sun, 14 Aug 2011) $
40 * @author Rodney Waldhoff
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 if (procedure == null) {
56 throw new IllegalArgumentException("Procedure argument was null");
57 }
58 this.procedure = procedure;
59 }
60
61 /**
62 * {@inheritDoc}
63 */
64 public T evaluate() {
65 procedure.run();
66 return null;
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean equals(Object that) {
73 return that == this || (that instanceof ProcedureFunction<?> && equals((ProcedureFunction<?>) that));
74 }
75
76 /**
77 * Learn whether another ProcedureFunction is equal to this.
78 * @param that ProcedureFunction to test
79 * @return boolean
80 */
81 public boolean equals(ProcedureFunction<?> that) {
82 return null != that && (null == procedure ? null == that.procedure : procedure.equals(that.procedure));
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 public int hashCode() {
89 int hash = "ProcedureFunction".hashCode();
90 if (null != procedure) {
91 hash ^= procedure.hashCode();
92 }
93 return hash;
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 public String toString() {
100 return "ProcedureFunction<" + procedure + ">";
101 }
102
103 /**
104 * Adapt a Procedure as a Function.
105 * @param <T> the returned value type.
106 * @param procedure to adapt
107 * @return ProcedureFunction<T>
108 */
109 public static <T> ProcedureFunction<T> adapt(Procedure procedure) {
110 return null == procedure ? null : new ProcedureFunction<T>(procedure);
111 }
112
113 }