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.functor.UnaryFunction;
23
24 /**
25 * A {@link BinaryPredicate BinaryPredicate} composed of
26 * one binary predicate, <i>p</i>, and two unary
27 * functions, <i>f</i> and <i>g</i>,
28 * evaluating the ordered parameters <i>x</i>, <i>y</i>
29 * to <code><i>p</i>(<i>f</i>(<i>x</i>),<i>g</i>(<i>y</i>))</code>.
30 * <p>
31 * Note that although this class implements
32 * {@link Serializable}, a given instance will
33 * only be truly <code>Serializable</code> if all the
34 * underlying functors are. Attempts to serialize
35 * an instance whose delegates are not all
36 * <code>Serializable</code> will result in an exception.
37 * </p>
38 * @version $Revision: 1156337 $ $Date: 2011-08-10 21:44:54 +0200 (Wed, 10 Aug 2011) $
39 * @author Rodney Waldhoff
40 */
41 public class UnaryCompositeBinaryPredicate<L, R> implements BinaryPredicate<L, R>, Serializable {
42 /**
43 * serialVersionUID declaration.
44 */
45 private static final long serialVersionUID = 3841123079006929493L;
46
47 private static class Helper<G, H, L, R> implements BinaryPredicate<L, R>, Serializable {
48 /**
49 * serialVersionUID declaration.
50 */
51 private static final long serialVersionUID = -3463108273324567825L;
52 private BinaryPredicate<? super G, ? super H> f;
53 private UnaryFunction<? super L, ? extends G> g;
54 private UnaryFunction<? super R, ? extends H> h;
55
56 /**
57 * Create a new Helper.
58 * @param f BinaryPredicate to test <i>output(</i><code>f</code><i>), output(</i><code>g</code><i>)</i>
59 * @param g left UnaryFunction
60 * @param h right UnaryFunction
61 */
62 public Helper(BinaryPredicate<? super G, ? super H> f, UnaryFunction<? super L, ? extends G> g,
63 UnaryFunction<? super R, ? extends H> h) {
64 this.f = f;
65 this.g = g;
66 this.h = h;
67 }
68
69 /**
70 * {@inheritDoc}
71 */
72 public boolean test(L left, R right) {
73 return f.test(g.evaluate(left), h.evaluate(right));
74 }
75 }
76
77 // attributes
78 // ------------------------------------------------------------------------
79 private final Helper<?, ?, L, R> helper;
80
81 // constructor
82 // ------------------------------------------------------------------------
83 /**
84 * Create a new UnaryCompositeBinaryPredicate.
85 * @param f BinaryPredicate to test <i>output(</i><code>f</code><i>), output(</i><code>g</code><i>)</i>
86 * @param g left UnaryFunction
87 * @param h right UnaryFunction
88 */
89 public <G, H> UnaryCompositeBinaryPredicate(final BinaryPredicate<? super G, ? super H> f,
90 final UnaryFunction<? super L, ? extends G> g, final UnaryFunction<? super R, ? extends H> h) {
91 if (f == null) {
92 throw new IllegalArgumentException("BinaryPredicate must not be null");
93 }
94 if (g == null || h == null) {
95 throw new IllegalArgumentException("Left and right UnaryFunctions may not be null");
96 }
97 helper = new Helper<G, H, L, R>(f, g, h);
98 }
99
100 // function interface
101 // ------------------------------------------------------------------------
102 /**
103 * {@inheritDoc}
104 */
105 public boolean test(L left, R right) {
106 return helper.test(left, right);
107 }
108
109 /**
110 * {@inheritDoc}
111 */
112 public boolean equals(Object that) {
113 return that == this || (that instanceof UnaryCompositeBinaryPredicate<?, ?>
114 && equals((UnaryCompositeBinaryPredicate<?, ?>) that));
115 }
116
117 /**
118 * Learn whether another UnaryCompositeBinaryPredicate is equal to this.
119 * @param that UnaryCompositeBinaryPredicate to test
120 * @return boolean
121 */
122 public boolean equals(UnaryCompositeBinaryPredicate<?, ?> that) {
123 return null != that && helper.f.equals(that.helper.f) && helper.g.equals(that.helper.g)
124 && helper.h.equals(that.helper.h);
125 }
126
127 /**
128 * {@inheritDoc}
129 */
130 public int hashCode() {
131 int hash = "UnaryCompositeBinaryPredicate".hashCode();
132 hash <<= 4;
133 hash ^= helper.f.hashCode();
134 hash <<= 4;
135 hash ^= helper.g.hashCode();
136 hash <<= 4;
137 hash ^= helper.h.hashCode();
138 return hash;
139 }
140
141 /**
142 * {@inheritDoc}
143 */
144 public String toString() {
145 return "UnaryCompositeBinaryPredicate<" + helper.f + ";" + helper.g + ";" + helper.h + ">";
146 }
147
148 }