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.UnaryFunction;
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 UnaryFunction UnaryFunction} 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 * @param <A> the argument type.
39 * @version $Revision: 1365377 $ $Date: 2012-07-24 21:59:23 -0300 (Tue, 24 Jul 2012) $
40 */
41 public final class UnaryPredicateUnaryFunction<A> implements UnaryFunction<A, Boolean>, Serializable {
42 /**
43 * serialVersionUID declaration.
44 */
45 private static final long serialVersionUID = 5660724725036398625L;
46 /** The {@link UnaryPredicate UnaryPredicate} I'm wrapping. */
47 private final UnaryPredicate<? super A> predicate;
48
49 /**
50 * Create a new UnaryPredicateUnaryFunction.
51 * @param predicate to adapt
52 */
53 public UnaryPredicateUnaryFunction(UnaryPredicate<? super A> predicate) {
54 this.predicate = Validate.notNull(predicate, "UnaryPredicate argument was null");
55 }
56
57 /**
58 * {@inheritDoc}
59 * Returns <code>Boolean.TRUE</code> (<code>Boolean.FALSE</code>)
60 * when the {@link UnaryPredicate#test test} method of my underlying
61 * predicate returns <code>true</code> (<code>false</code>).
62 *
63 * @return a non-<code>null</code> <code>Boolean</code> instance
64 */
65 public Boolean evaluate(A obj) {
66 return Boolean.valueOf(predicate.test(obj));
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 @Override
73 public boolean equals(Object that) {
74 return that == this
75 || (that instanceof UnaryPredicateUnaryFunction<?> && equals((UnaryPredicateUnaryFunction<?>) that));
76 }
77
78 /**
79 * Learn whether another UnaryPredicateUnaryFunction is equal to this.
80 * @param that UnaryPredicateUnaryFunction to test
81 * @return boolean
82 */
83 public boolean equals(UnaryPredicateUnaryFunction<?> that) {
84 return null != that && predicate.equals(that.predicate);
85 }
86
87 /**
88 * {@inheritDoc}
89 */
90 @Override
91 public int hashCode() {
92 int hash = "UnaryPredicateUnaryFunction".hashCode();
93 hash ^= predicate.hashCode();
94 return hash;
95 }
96
97 /**
98 * {@inheritDoc}
99 */
100 @Override
101 public String toString() {
102 return "UnaryPredicateUnaryFunction<" + predicate + ">";
103 }
104
105 /**
106 * Adapt a UnaryPredicate to the UnaryFunction interface.
107 * @param <A> the argument type.
108 * @param predicate to adapt
109 * @return UnaryPredicateUnaryFunction
110 */
111 public static <A> UnaryPredicateUnaryFunction<A> adapt(UnaryPredicate<? super A> predicate) {
112 return null == predicate ? null : new UnaryPredicateUnaryFunction<A>(predicate);
113 }
114
115 }