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
24 /**
25 * Adapts a
26 * {@link UnaryPredicate UnaryPredicate}
27 * to the
28 * {@link UnaryFunction UnaryFunction} interface.
29 * <p/>
30 * Note that although this class implements
31 * {@link Serializable}, a given instance will
32 * only be truly <code>Serializable</code> if the
33 * underlying predicate is. Attempts to serialize
34 * an instance whose delegate is not
35 * <code>Serializable</code> will result in an exception.
36 *
37 * @param <A> the argument type.
38 * @version $Revision: 1157655 $ $Date: 2011-08-14 22:25:24 +0200 (Sun, 14 Aug 2011) $
39 * @author Rodney Waldhoff
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 if (predicate == null) {
55 throw new IllegalArgumentException("UnaryPredicate argument was null");
56 }
57 this.predicate = predicate;
58 }
59
60 /**
61 * {@inheritDoc}
62 * Returns <code>Boolean.TRUE</code> (<code>Boolean.FALSE</code>)
63 * when the {@link UnaryPredicate#test test} method of my underlying
64 * predicate returns <code>true</code> (<code>false</code>).
65 *
66 * @return a non-<code>null</code> <code>Boolean</code> instance
67 */
68 public Boolean evaluate(A obj) {
69 return predicate.test(obj);
70 }
71
72 /**
73 * {@inheritDoc}
74 */
75 public boolean equals(Object that) {
76 return that == this
77 || (that instanceof UnaryPredicateUnaryFunction<?> && equals((UnaryPredicateUnaryFunction<?>) that));
78 }
79
80 /**
81 * Learn whether another UnaryPredicateUnaryFunction is equal to this.
82 * @param that UnaryPredicateUnaryFunction to test
83 * @return boolean
84 */
85 public boolean equals(UnaryPredicateUnaryFunction<?> that) {
86 return null != that && (null == predicate ? null == that.predicate : predicate.equals(that.predicate));
87 }
88
89 /**
90 * {@inheritDoc}
91 */
92 public int hashCode() {
93 int hash = "UnaryPredicateUnaryFunction".hashCode();
94 if (null != predicate) {
95 hash ^= predicate.hashCode();
96 }
97 return hash;
98 }
99
100 /**
101 * {@inheritDoc}
102 */
103 public String toString() {
104 return "UnaryPredicateUnaryFunction<" + predicate + ">";
105 }
106
107 /**
108 * Adapt a UnaryPredicate to the UnaryFunction interface.
109 * @param <A> the argument type.
110 * @param predicate to adapt
111 * @return UnaryPredicateUnaryFunction
112 */
113 public static <A> UnaryPredicateUnaryFunction<A> adapt(UnaryPredicate<? super A> predicate) {
114 return null == predicate ? null : new UnaryPredicateUnaryFunction<A>(predicate);
115 }
116
117 }