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.BinaryFunction;
22 import org.apache.commons.functor.BinaryPredicate;
23
24 /**
25 * A {@link BinaryFunction BinaryFunction}
26 * similiar to Java's "ternary"
27 * or "conditional" operator (<code>? :</code>).
28 * Given a {@link BinaryPredicate predicate}
29 * <i>p</i> and {@link BinaryFunction functions}
30 * <i>f</i> and <i>g</i>, {@link #evaluate evaluates}
31 * to
32 * <code>p.test(x,y) ? f.evaluate(x,y) : g.evaluate(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 * @version $Revision: 1166381 $ $Date: 2011-09-07 22:19:48 +0200 (Wed, 07 Sep 2011) $
42 * @author Rodney Waldhoff
43 */
44 public final class ConditionalBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
45 /**
46 * serialVersionUID declaration.
47 */
48 private static final long serialVersionUID = -994698971284481482L;
49
50 /** Base hash integer used to shift hash */
51 private static final int HASH_SHIFT = 4;
52 // attributes
53 // ------------------------------------------------------------------------
54 private final BinaryPredicate<? super L, ? super R> ifPred;
55 private final BinaryFunction<? super L, ? super R, ? extends T> thenFunc;
56 private final BinaryFunction<? super L, ? super R, ? extends T> elseFunc;
57
58 // constructor
59 // ------------------------------------------------------------------------
60 /**
61 * Create a new ConditionalBinaryFunction.
62 * @param ifPred if
63 * @param thenFunc then
64 * @param elseFunc else
65 */
66 public ConditionalBinaryFunction(BinaryPredicate<? super L, ? super R> ifPred,
67 BinaryFunction<? super L, ? super R, ? extends T> thenFunc,
68 BinaryFunction<? super L, ? super R, ? extends T> elseFunc) {
69 if (ifPred == null) {
70 throw new IllegalArgumentException("BinaryPredicate argument was null");
71 }
72 if (thenFunc == null || elseFunc == null) {
73 throw new IllegalArgumentException("One or more BinaryFunction arguments was null");
74 }
75 this.ifPred = ifPred;
76 this.thenFunc = thenFunc;
77 this.elseFunc = elseFunc;
78 }
79
80 // predicate interface
81 // ------------------------------------------------------------------------
82 /**
83 * {@inheritDoc}
84 */
85 public T evaluate(L left, R right) {
86 if (ifPred.test(left, right)) {
87 return thenFunc.evaluate(left, right);
88 } else {
89 return elseFunc.evaluate(left, right);
90 }
91 }
92
93 /**
94 * {@inheritDoc}
95 */
96 public boolean equals(Object that) {
97 return that == this || (that instanceof ConditionalBinaryFunction<?, ?, ?>
98 && equals((ConditionalBinaryFunction<?, ?, ?>) that));
99 }
100
101 /**
102 * Learn whether another ConditionalBinaryFunction is equal to this.
103 * @param that ConditionalBinaryFunction to test
104 * @return boolean
105 */
106 public boolean equals(ConditionalBinaryFunction<?, ?, ?> that) {
107 return null != that
108 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
109 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc))
110 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc));
111 }
112
113 /**
114 * {@inheritDoc}
115 */
116 public int hashCode() {
117 int hash = "ConditionalBinaryFunction".hashCode();
118 if (null != ifPred) {
119 hash <<= HASH_SHIFT;
120 hash ^= ifPred.hashCode();
121 }
122 if (null != thenFunc) {
123 hash <<= HASH_SHIFT;
124 hash ^= thenFunc.hashCode();
125 }
126 if (null != elseFunc) {
127 hash <<= HASH_SHIFT;
128 hash ^= elseFunc.hashCode();
129 }
130 return hash;
131 }
132
133 /**
134 * {@inheritDoc}
135 */
136 public String toString() {
137 return "ConditionalBinaryFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";
138 }
139
140 }