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 import org.apache.commons.lang3.Validate;
23
24 /**
25 * A {@link Predicate Predicate}
26 * similiar to Java's "ternary"
27 * or "conditional" operator (<code>? :</code>).
28 * Given three {@link Predicate predicates}
29 * <i>p</i>, <i>q</i>, <i>r</i>,
30 * {@link #test tests}
31 * to
32 * <code>p.test() ? q.test() : r.test()</code>.
33 * <p>
34 * Note that although this class implements
35 * {@link Serializable}, a given instance will
36 * only be truly <code>Serializable</code> if all the
37 * underlying functors are. Attempts to serialize
38 * an instance whose delegates are not all
39 * <code>Serializable</code> will result in an exception.
40 * </p>
41 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
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 /**
54 * the condition to be evaluated.
55 */
56 private final Predicate ifPred;
57 /**
58 * the predicate executed if the condition is satisfied.
59 */
60 private final Predicate thenPred;
61 /**
62 * the predicate executed if the condition is not satisfied.
63 */
64 private final Predicate elsePred;
65
66 // constructor
67 // ------------------------------------------------------------------------
68 /**
69 * Create a new ConditionalPredicate.
70 * @param ifPred if
71 * @param thenPred then
72 * @param elsePred else
73 */
74 public ConditionalPredicate(Predicate ifPred, Predicate thenPred, Predicate elsePred) {
75 this.ifPred = Validate.notNull(ifPred, "'if' Predicate argument was null");
76 this.thenPred = Validate.notNull(thenPred, "'then' Predicate argument was null");
77 this.elsePred = Validate.notNull(elsePred, "'else' Predicate argument was null");
78 }
79
80 // predicate interface
81 // ------------------------------------------------------------------------
82 /**
83 * {@inheritDoc}
84 */
85 public boolean test() {
86 return ifPred.test() ? thenPred.test() : elsePred.test();
87 }
88
89 /**
90 * {@inheritDoc}
91 */
92 @Override
93 public boolean equals(Object that) {
94 return that == this || (that instanceof ConditionalPredicate && equals((ConditionalPredicate) that));
95 }
96
97 /**
98 * Learn whether another ConditionalPredicate is equal to this.
99 * @param that ConditionalPredicate to test
100 * @return boolean
101 */
102 public boolean equals(ConditionalPredicate that) {
103 return null != that
104 && ifPred.equals(that.ifPred)
105 && thenPred.equals(that.thenPred)
106 && elsePred.equals(that.elsePred);
107 }
108
109 /**
110 * {@inheritDoc}
111 */
112 @Override
113 public int hashCode() {
114 int hash = "ConditionalPredicate".hashCode();
115 hash <<= HASH_SHIFT;
116 hash ^= ifPred.hashCode();
117 hash <<= HASH_SHIFT;
118 hash ^= thenPred.hashCode();
119 hash <<= HASH_SHIFT;
120 hash ^= elsePred.hashCode();
121 return hash;
122 }
123
124 /**
125 * {@inheritDoc}
126 */
127 @Override
128 public String toString() {
129 return "ConditionalPredicate<" + ifPred + "?" + thenPred + ":" + elsePred + ">";
130 }
131
132 }