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.BinaryPredicate;
22 import org.apache.commons.lang3.Validate;
23
24 /**
25 * A {@link BinaryPredicate BinaryPredicate}
26 * similiar to Java's "ternary"
27 * or "conditional" operator (<code>? :</code>).
28 * Given three {@link BinaryPredicate predicates}
29 * <i>p</i>, <i>q</i>, <i>r</i>,
30 * {@link #test tests}
31 * to
32 * <code>p.test(x,y) ? q.test(x,y) : r.test(x,y)</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 * @param <L> the left argument type.
42 * @param <R> the right argument type.
43 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
44 */
45 public final class ConditionalBinaryPredicate<L, R> implements BinaryPredicate<L, R>, Serializable {
46 /**
47 * serialVersionUID declaration.
48 */
49 private static final long serialVersionUID = -4511946801764080748L;
50
51 /** Base hash integer used to shift hash. */
52 private static final int HASH_SHIFT = 4;
53 // attributes
54 // ------------------------------------------------------------------------
55 /**
56 * the condition to be evaluated.
57 */
58 private final BinaryPredicate<? super L, ? super R> ifPred;
59 /**
60 * the predicate executed if the condition is satisfied.
61 */
62 private final BinaryPredicate<? super L, ? super R> thenPred;
63 /**
64 * the predicate executed if the condition is not satisfied.
65 */
66 private final BinaryPredicate<? super L, ? super R> elsePred;
67
68 // constructor
69 // ------------------------------------------------------------------------
70 /**
71 * Create a new ConditionalBinaryPredicate.
72 * @param ifPred if
73 * @param thenPred then
74 * @param elsePred else
75 */
76 public ConditionalBinaryPredicate(BinaryPredicate<? super L, ? super R> ifPred,
77 BinaryPredicate<? super L, ? super R> thenPred, BinaryPredicate<? super L, ? super R> elsePred) {
78 this.ifPred = Validate.notNull(ifPred, "'if' BinaryPredicate argument was null");
79 this.thenPred = Validate.notNull(thenPred, "'then' BinaryPredicate argument was null");
80 this.elsePred = Validate.notNull(elsePred, "'else' BinaryPredicate argument was null");
81 }
82
83 // predicate interface
84 // ------------------------------------------------------------------------
85 /**
86 * {@inheritDoc}
87 */
88 public boolean test(L left, R right) {
89 return ifPred.test(left, right) ? thenPred.test(left, right) : elsePred.test(left, right);
90 }
91
92 /**
93 * {@inheritDoc}
94 */
95 @Override
96 public boolean equals(Object that) {
97 return that == this || (that instanceof ConditionalBinaryPredicate<?, ?>
98 && equals((ConditionalBinaryPredicate<?, ?>) that));
99 }
100
101 /**
102 * Learn whether another ConditionalBinaryPredicate is equal to this.
103 * @param that ConditionalBinaryPredicate to test
104 * @return boolean
105 */
106 public boolean equals(ConditionalBinaryPredicate<?, ?> that) {
107 return null != that
108 && ifPred.equals(that.ifPred)
109 && thenPred.equals(that.thenPred)
110 && elsePred.equals(that.elsePred);
111 }
112
113 /**
114 * {@inheritDoc}
115 */
116 @Override
117 public int hashCode() {
118 int hash = "ConditionalBinaryPredicate".hashCode();
119 hash <<= HASH_SHIFT;
120 hash ^= ifPred.hashCode();
121 hash <<= HASH_SHIFT;
122 hash ^= thenPred.hashCode();
123 hash <<= HASH_SHIFT;
124 hash ^= elsePred.hashCode();
125 return hash;
126 }
127
128 /**
129 * {@inheritDoc}
130 */
131 @Override
132 public String toString() {
133 return "ConditionalBinaryPredicate<" + ifPred + "?" + thenPred + ":" + elsePred + ">";
134 }
135
136 }