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.Predicate;
23 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link Predicate Predicate}
28 * to the
29 * {@link Function Function} interface.
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 predicate is. Attempts to serialize
35 * an instance whose delegate is not
36 * <code>Serializable</code> will result in an exception.
37 *
38 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
39 */
40 public final class PredicateFunction implements Function<Boolean>, Serializable {
41 /**
42 * serialVersionUID declaration.
43 */
44 private static final long serialVersionUID = -8858981355549412629L;
45 /** The {@link Predicate Predicate} I'm wrapping. */
46 private final Predicate predicate;
47
48 /**
49 * Create a new PredicateFunction.
50 * @param predicate to adapt
51 */
52 public PredicateFunction(Predicate predicate) {
53 this.predicate = Validate.notNull(predicate, "Predicate argument was null");
54 }
55
56 /**
57 * {@inheritDoc}
58 * Returns <code>Boolean.TRUE</code> (<code>Boolean.FALSE</code>)
59 * when the {@link Predicate#test test} method of my underlying
60 * predicate returns <code>true</code> (<code>false</code>).
61 *
62 * @return a non-<code>null</code> <code>Boolean</code> instance
63 */
64 public Boolean evaluate() {
65 return Boolean.valueOf(predicate.test());
66 }
67
68 /**
69 * {@inheritDoc}
70 */
71 @Override
72 public boolean equals(Object that) {
73 return that == this || (that instanceof PredicateFunction && equals((PredicateFunction) that));
74 }
75
76 /**
77 * Learn whether another PredicateFunction is equal to this.
78 * @param that PredicateFunction to test
79 * @return boolean
80 */
81 public boolean equals(PredicateFunction that) {
82 return null != that && predicate.equals(that.predicate);
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 @Override
89 public int hashCode() {
90 int hash = "PredicateFunction".hashCode();
91 hash ^= predicate.hashCode();
92 return hash;
93 }
94
95 /**
96 * {@inheritDoc}
97 */
98 @Override
99 public String toString() {
100 return "PredicateFunction<" + predicate + ">";
101 }
102
103 /**
104 * Adapt a Predicate to the Function interface.
105 * @param predicate to adapt
106 * @return PredicateFunction
107 */
108 public static PredicateFunction adapt(Predicate predicate) {
109 return null == predicate ? null : new PredicateFunction(predicate);
110 }
111
112 }