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.Predicate;
22 import org.apache.commons.functor.UnaryPredicate;
23
24 /**
25 * Adapts a
26 * {@link Predicate Predicate}
27 * to the
28 * {@link UnaryPredicate UnaryPredicate} interface
29 * by ignoring the given argument.
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 functor is. Attempts to serialize
35 * an instance whose delegate is not
36 * <code>Serializable</code> will result in an exception.
37 *
38 * @param <A> the argument type.
39 * @version $Revision: 1157628 $ $Date: 2011-08-14 22:04:52 +0200 (Sun, 14 Aug 2011) $
40 * @author Rodney Waldhoff
41 */
42 public final class PredicateUnaryPredicate<A> implements UnaryPredicate<A>, Serializable {
43 /**
44 * serialVersionUID declaration.
45 */
46 private static final long serialVersionUID = -5168896606842881702L;
47 /** The {@link Predicate Predicate} I'm wrapping. */
48 private final Predicate predicate;
49
50 /**
51 * Create a new PredicateUnaryPredicate.
52 * @param predicate to adapt
53 */
54 public PredicateUnaryPredicate(Predicate predicate) {
55 if (predicate == null) {
56 throw new IllegalArgumentException("Predicate argument was null");
57 }
58 this.predicate = predicate;
59 }
60
61 /**
62 * {@inheritDoc}
63 */
64 public boolean test(Object obj) {
65 return predicate.test();
66 }
67
68 /**
69 * {@inheritDoc}
70 */
71 public boolean equals(Object that) {
72 return that == this || (that instanceof PredicateUnaryPredicate<?>
73 && equals((PredicateUnaryPredicate<?>) that));
74 }
75
76 /**
77 * Learn whether a given PredicateUnaryPredicate is equal to this.
78 * @param that PredicateUnaryPredicate to test
79 * @return boolean
80 */
81 public boolean equals(PredicateUnaryPredicate<?> that) {
82 return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 public int hashCode() {
89 int hash = "PredicateUnaryPredicate".hashCode();
90 if (null != predicate) {
91 hash ^= predicate.hashCode();
92 }
93 return hash;
94 }
95
96 /**
97 * {@inheritDoc}
98 */
99 public String toString() {
100 return "PredicateUnaryPredicate<" + predicate + ">";
101 }
102
103 /**
104 * Adapt a Predicate to the UnaryPredicate interface.
105 * @param <A> the argument type.
106 * @param predicate to adapt
107 * @return PredicateUnaryPredicate<A>
108 */
109 public static <A> PredicateUnaryPredicate<A> adapt(Predicate predicate) {
110 return null == predicate ? null : new PredicateUnaryPredicate<A>(predicate);
111 }
112
113 }