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 import org.apache.commons.lang3.Validate;
24
25 /**
26 * Adapts a
27 * {@link UnaryPredicate UnaryPredicate}
28 * to the
29 * {@link Predicate Predicate} interface
30 * using a constant unary argument.
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 objects are. Attempts to serialize
36 * an instance whose delegates are not
37 * <code>Serializable</code> will result in an exception.
38 *
39 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
40 */
41 public final class BoundPredicate implements Predicate, Serializable {
42 /**
43 * serialVersionUID declaration.
44 */
45 private static final long serialVersionUID = -5721164265625291834L;
46 /** The {@link UnaryPredicate UnaryPredicate} I'm wrapping. */
47 private final UnaryPredicate<Object> predicate;
48 /** The parameter to pass to {@code predicate}. */
49 private final Object param;
50
51 /**
52 * Create a new BoundPredicate instance.
53 * @param <A> input type
54 * @param predicate the predicate to adapt
55 * @param arg the constant argument to use
56 */
57 @SuppressWarnings("unchecked")
58 public <A> BoundPredicate(UnaryPredicate<? super A> predicate, A arg) {
59 this.predicate =
60 (UnaryPredicate<Object>) Validate.notNull(predicate,
61 "UnaryPredicate argument was null");
62 this.param = arg;
63 }
64
65 /**
66 * {@inheritDoc}
67 */
68 public boolean test() {
69 return predicate.test(param);
70 }
71
72 /**
73 * {@inheritDoc}
74 */
75 @Override
76 public boolean equals(Object that) {
77 return that == this || (that instanceof BoundPredicate && equals((BoundPredicate) that));
78 }
79
80 /**
81 * Learn whether another BoundPredicate is equal to this.
82 * @param that BoundPredicate to test
83 * @return boolean
84 */
85 public boolean equals(BoundPredicate that) {
86 return null != that
87 && predicate.equals(that.predicate)
88 && (null == param ? null == that.param : param.equals(that.param));
89
90 }
91
92 /**
93 * {@inheritDoc}
94 */
95 @Override
96 public int hashCode() {
97 int hash = "BoundPredicate".hashCode();
98 hash <<= 2;
99 hash ^= predicate.hashCode();
100 if (null != param) {
101 hash <<= 2;
102 hash ^= param.hashCode();
103 }
104 return hash;
105 }
106
107 /**
108 * {@inheritDoc}
109 */
110 @Override
111 public String toString() {
112 return "BoundPredicate<" + predicate + "(" + param + ")>";
113 }
114
115 /**
116 * Adapt the given, possibly-<code>null</code>,
117 * {@link UnaryPredicate UnaryPredicate} to the
118 * {@link Predicate Predicate} interface by binding
119 * the specified <code>Object</code> as a constant
120 * argument.
121 * When the given <code>UnaryPredicate</code> is <code>null</code>,
122 * returns <code>null</code>.
123 *
124 * @param <A> input type
125 * @param predicate the possibly-<code>null</code>
126 * {@link UnaryPredicate UnaryPredicate} to adapt
127 * @param arg the object to bind as a constant argument
128 * @return a <code>BoundPredicate</code> wrapping the given
129 * {@link UnaryPredicate UnaryPredicate}, or <code>null</code>
130 * if the given <code>UnaryPredicate</code> is <code>null</code>
131 */
132 public static <A> BoundPredicate bind(UnaryPredicate<? super A> predicate, A arg) {
133 return null == predicate ? null : new BoundPredicate(predicate, arg);
134 }
135
136 }