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 import org.apache.commons.lang3.Validate;
24
25 /**
26 * A {@link BinaryFunction BinaryFunction}
27 * similiar to Java's "ternary"
28 * or "conditional" operator (<code>? :</code>).
29 * Given a {@link BinaryPredicate predicate}
30 * <i>p</i> and {@link BinaryFunction functions}
31 * <i>f</i> and <i>g</i>, {@link #evaluate evaluates}
32 * to
33 * <code>p.test(x,y) ? f.evaluate(x,y) : g.evaluate(x,y)</code>.
34 * <p>
35 * Note that although this class implements
36 * {@link Serializable}, a given instance will
37 * only be truly <code>Serializable</code> if all the
38 * underlying functors are. Attempts to serialize
39 * an instance whose delegates are not all
40 * <code>Serializable</code> will result in an exception.
41 * </p>
42 * @param <L> the left argument type.
43 * @param <R> the right argument type.
44 * @param <T> the output function returned value type.
45 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
46 */
47 public final class ConditionalBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
48 /**
49 * serialVersionUID declaration.
50 */
51 private static final long serialVersionUID = -994698971284481482L;
52
53 /** Base hash integer used to shift hash. */
54 private static final int HASH_SHIFT = 4;
55 // attributes
56 // ------------------------------------------------------------------------
57 /**
58 * the condition to be evaluated.
59 */
60 private final BinaryPredicate<? super L, ? super R> ifPred;
61 /**
62 * the function executed if the condition is satisfied.
63 */
64 private final BinaryFunction<? super L, ? super R, ? extends T> thenFunc;
65 /**
66 * the function executed if the condition is not satisfied.
67 */
68 private final BinaryFunction<? super L, ? super R, ? extends T> elseFunc;
69
70 // constructor
71 // ------------------------------------------------------------------------
72 /**
73 * Create a new ConditionalBinaryFunction.
74 * @param ifPred if
75 * @param thenFunc then
76 * @param elseFunc else
77 */
78 public ConditionalBinaryFunction(BinaryPredicate<? super L, ? super R> ifPred,
79 BinaryFunction<? super L, ? super R, ? extends T> thenFunc,
80 BinaryFunction<? super L, ? super R, ? extends T> elseFunc) {
81 this.ifPred = Validate.notNull(ifPred, "BinaryPredicate argument was null");
82 this.thenFunc = Validate.notNull(thenFunc, "'then' BinaryFunction argument was null");
83 this.elseFunc = Validate.notNull(elseFunc, "'else' BinaryFunction argument was null");
84 }
85
86 // predicate interface
87 // ------------------------------------------------------------------------
88 /**
89 * {@inheritDoc}
90 */
91 public T evaluate(L left, R right) {
92 if (ifPred.test(left, right)) {
93 return thenFunc.evaluate(left, right);
94 } else {
95 return elseFunc.evaluate(left, right);
96 }
97 }
98
99 /**
100 * {@inheritDoc}
101 */
102 @Override
103 public boolean equals(Object that) {
104 return that == this || (that instanceof ConditionalBinaryFunction<?, ?, ?>
105 && equals((ConditionalBinaryFunction<?, ?, ?>) that));
106 }
107
108 /**
109 * Learn whether another ConditionalBinaryFunction is equal to this.
110 * @param that ConditionalBinaryFunction to test
111 * @return boolean
112 */
113 public boolean equals(ConditionalBinaryFunction<?, ?, ?> that) {
114 return null != that
115 && ifPred.equals(that.ifPred)
116 && thenFunc.equals(that.thenFunc)
117 && elseFunc.equals(that.elseFunc);
118 }
119
120 /**
121 * {@inheritDoc}
122 */
123 @Override
124 public int hashCode() {
125 int hash = "ConditionalBinaryFunction".hashCode();
126 hash <<= HASH_SHIFT;
127 hash ^= ifPred.hashCode();
128 hash <<= HASH_SHIFT;
129 hash ^= thenFunc.hashCode();
130 hash <<= HASH_SHIFT;
131 hash ^= elseFunc.hashCode();
132 return hash;
133 }
134
135 /**
136 * {@inheritDoc}
137 */
138 @Override
139 public String toString() {
140 return "ConditionalBinaryFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";
141 }
142
143 }