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.composite;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.Predicate;
22
23 /**
24 * A {@link Predicate Predicate}
25 * similiar to Java's "ternary"
26 * or "conditional" operator (<code>? :</code>).
27 * Given three {@link Predicate predicates}
28 * <i>p</i>, <i>q</i>, <i>r</i>,
29 * {@link #test tests}
30 * to
31 * <code>p.test() ? q.test() : r.test()</code>.
32 * <p>
33 * Note that although this class implements
34 * {@link Serializable}, a given instance will
35 * only be truly <code>Serializable</code> if all the
36 * underlying functors are. Attempts to serialize
37 * an instance whose delegates are not all
38 * <code>Serializable</code> will result in an exception.
39 * </p>
40 * @version $Revision: 1166388 $ $Date: 2011-09-07 22:29:02 +0200 (Wed, 07 Sep 2011) $
41 * @author Rodney Waldhoff
42 */
43 public final class ConditionalPredicate implements Predicate, Serializable {
44 /**
45 * serialVersionUID declaration.
46 */
47 private static final long serialVersionUID = 7333505000745854098L;
48
49 /** Base hash integer used to shift hash */
50 private static final int HASH_SHIFT = 4;
51 // attributes
52 // ------------------------------------------------------------------------
53 private final Predicate ifPred;
54 private final Predicate thenPred;
55 private final Predicate elsePred;
56
57 // constructor
58 // ------------------------------------------------------------------------
59 /**
60 * Create a new ConditionalPredicate.
61 * @param ifPred if
62 * @param thenPred then
63 * @param elsePred else
64 */
65 public ConditionalPredicate(Predicate ifPred, Predicate thenPred, Predicate elsePred) {
66 if (ifPred == null || thenPred == null || elsePred == null) {
67 throw new IllegalArgumentException("One or more Predicate arguments was null");
68 }
69 this.ifPred = ifPred;
70 this.thenPred = thenPred;
71 this.elsePred = elsePred;
72 }
73
74 // predicate interface
75 // ------------------------------------------------------------------------
76 /**
77 * {@inheritDoc}
78 */
79 public boolean test() {
80 return ifPred.test() ? thenPred.test() : elsePred.test();
81 }
82
83 /**
84 * {@inheritDoc}
85 */
86 public boolean equals(Object that) {
87 return that == this || (that instanceof ConditionalPredicate && equals((ConditionalPredicate) that));
88 }
89
90 /**
91 * Learn whether another ConditionalPredicate is equal to this.
92 * @param that ConditionalPredicate to test
93 * @return boolean
94 */
95 public boolean equals(ConditionalPredicate that) {
96 return null != that
97 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
98 && (null == thenPred ? null == that.thenPred : thenPred.equals(that.thenPred))
99 && (null == elsePred ? null == that.elsePred : elsePred.equals(that.elsePred));
100 }
101
102 /**
103 * {@inheritDoc}
104 */
105 public int hashCode() {
106 int hash = "ConditionalPredicate".hashCode();
107 if (null != ifPred) {
108 hash <<= HASH_SHIFT;
109 hash ^= ifPred.hashCode();
110 }
111 if (null != thenPred) {
112 hash <<= HASH_SHIFT;
113 hash ^= thenPred.hashCode();
114 }
115 if (null != elsePred) {
116 hash <<= HASH_SHIFT;
117 hash ^= elsePred.hashCode();
118 }
119 return hash;
120 }
121
122 /**
123 * {@inheritDoc}
124 */
125 public String toString() {
126 return "ConditionalPredicate<" + ifPred + "?" + thenPred + ":" + elsePred + ">";
127 }
128
129 }