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.core;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.BinaryPredicate;
22 import org.apache.commons.functor.UnaryPredicate;
23 import org.apache.commons.functor.adapter.RightBoundPredicate;
24
25 /**
26 * {@link #test Tests}
27 * <code>true</code> iff its arguments are
28 * {@link Object#equals equal} or both
29 * <code>null</code>.
30 * <p>
31 * This relation is
32 * an equivalence relation on
33 * the set of objects that adhere to the
34 * <code>Object.equals</code> contract.
35 * </p>
36 *
37 * @param <L> the left argument type.
38 * @param <R> the right argument type.
39 * @version $Revision: 1160389 $ $Date: 2011-08-22 21:31:15 +0200 (Mon, 22 Aug 2011) $
40 * @author Rodney Waldhoff
41 */
42 public final class IsEqual<L, R> implements BinaryPredicate<L, R>, Serializable {
43 // static attributes
44 // ------------------------------------------------------------------------
45 /**
46 * Basic IsEqual<Object, Object> instance.
47 */
48 public static final IsEqual<Object, Object> INSTANCE = IsEqual.<Object, Object>instance();
49 /**
50 * serialVersionUID declaration.
51 */
52 private static final long serialVersionUID = -6777016236280121159L;
53
54 // constructor
55 // ------------------------------------------------------------------------
56 /**
57 * Create a new IsEqual.
58 */
59 public IsEqual() {
60 }
61
62 // predicate interface
63 // ------------------------------------------------------------------------
64 /**
65 * {@inheritDoc}
66 */
67 public boolean test(L left, R right) {
68 return left == right || left != null && left.equals(right);
69 }
70
71 /**
72 * {@inheritDoc}
73 */
74 public boolean equals(Object that) {
75 return that instanceof IsEqual<?, ?>;
76 }
77
78 /**
79 * {@inheritDoc}
80 */
81 public int hashCode() {
82 return "IsEqual".hashCode();
83 }
84
85 /**
86 * {@inheritDoc}
87 */
88 public String toString() {
89 return "IsEqual";
90 }
91
92 // static methods
93 // ------------------------------------------------------------------------
94 /**
95 * Get an IsEqual instance.
96 * @param <L> the left argument type.
97 * @param <R> the right argument type.
98 * @return IsEqual
99 */
100 public static <L, R> IsEqual<L, R> instance() {
101 return new IsEqual<L, R>();
102 }
103
104 /**
105 * Get an IsEqual UnaryPredicate.
106 * @param <L> the left argument type.
107 * @param <R> the right argument type.
108 * @param object bound comparison object
109 * @return UnaryPredicate<L>
110 */
111 public static <L, R> UnaryPredicate<L> to(R object) {
112 return new RightBoundPredicate<L>(new IsEqual<L, R>(), object);
113 }
114 }