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.BinaryFunction;
22 import org.apache.commons.functor.BinaryProcedure;
23
24 /**
25 * Adapts a
26 * {@link BinaryProcedure BinaryProcedure}
27 * to the
28 * {@link BinaryFunction BinaryFunction} 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 <L> the left argument type.
39 * @param <R> the right argument type.
40 * @param <T> the returned value type.
41 * @version $Revision: 1157600 $ $Date: 2011-08-14 21:22:50 +0200 (Sun, 14 Aug 2011) $
42 * @author Rodney Waldhoff
43 */
44 public final class BinaryProcedureBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
45 /**
46 * serialVersionUID declaration.
47 */
48 private static final long serialVersionUID = 2099210273403668624L;
49 /** The {@link BinaryProcedure BinaryProcedure} I'm wrapping. */
50 private final BinaryProcedure<? super L, ? super R> procedure;
51
52 /**
53 * Create a new BinaryProcedureBinaryFunction.
54 * @param procedure to adapt as a BinaryFunction
55 */
56 public BinaryProcedureBinaryFunction(BinaryProcedure<? super L, ? super R> procedure) {
57 if (procedure == null) {
58 throw new IllegalArgumentException("BinaryProcedure argument was null");
59 }
60 this.procedure = procedure;
61 }
62
63 /**
64 * {@inheritDoc}
65 */
66 public T evaluate(L left, R right) {
67 procedure.run(left, right);
68 return null;
69 }
70
71 /**
72 * {@inheritDoc}
73 */
74 public boolean equals(Object that) {
75 return that == this || (that instanceof BinaryProcedureBinaryFunction<?, ?, ?>
76 && equals((BinaryProcedureBinaryFunction<?, ?, ?>) that));
77 }
78
79 /**
80 * Learn whether another BinaryProcedureBinaryFunction is equal to this.
81 * @param that the BinaryProcedureBinaryFunction to test
82 * @return boolean
83 */
84 public boolean equals(BinaryProcedureBinaryFunction<?, ?, ?> that) {
85 return null != that && (null == procedure ? null == that.procedure : procedure.equals(that.procedure));
86 }
87
88 /**
89 * {@inheritDoc}
90 */
91 public int hashCode() {
92 int hash = "BinaryProcedureBinaryFunction".hashCode();
93 if (null != procedure) {
94 hash ^= procedure.hashCode();
95 }
96 return hash;
97 }
98
99 /**
100 * {@inheritDoc}
101 */
102 public String toString() {
103 return "BinaryProcedureBinaryFunction<" + procedure + ">";
104 }
105
106 /**
107 * Adapt the given, possibly-<code>null</code>,
108 * {@link BinaryProcedure BinaryProcedure} to the
109 * {@link BinaryFunction BinaryFunction} interface.
110 * When the given <code>BinaryProcedure</code> is <code>null</code>,
111 * returns <code>null</code>.
112 *
113 * @param <L> the left argument type.
114 * @param <R> the right argument type.
115 * @param <T> the returned value type.
116 * @param procedure the possibly-<code>null</code>
117 * {@link BinaryFunction BinaryFunction} to adapt
118 * @return a <code>BinaryProcedureBinaryFunction</code> wrapping the given
119 * {@link BinaryFunction BinaryFunction}, or <code>null</code>
120 * if the given <code>BinaryFunction</code> is <code>null</code>
121 */
122 public static <L, R, T> BinaryProcedureBinaryFunction<L, R, T> adapt(BinaryProcedure<? super L, ? super R> procedure) {
123 return null == procedure ? null : new BinaryProcedureBinaryFunction<L, R, T>(procedure);
124 }
125
126 }