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.UnaryFunction;
22 import org.apache.commons.functor.UnaryPredicate;
23
24 /**
25 * A {@link UnaryFunction UnaryFunction}
26 * similiar to Java's "ternary"
27 * or "conditional" operator (<code>? :</code>).
28 * Given a {@link UnaryPredicate predicate}
29 * <i>p</i> and {@link UnaryFunction functions}
30 * <i>f</i> and <i>g</i>, {@link #evaluate evalautes}
31 * to
32 * <code>p.test(x) ? f.evaluate(x) : g.evaluate(x)</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: 1170778 $ $Date: 2011-09-14 21:15:01 +0200 (Wed, 14 Sep 2011) $
42 * @author Rodney Waldhoff
43 */
44 public final class ConditionalUnaryFunction<A, T> implements UnaryFunction<A, T>, Serializable {
45 /**
46 * serialVersionUID declaration.
47 */
48 private static final long serialVersionUID = -8152490481969255068L;
49
50 /** Base hash integer used to shift hash */
51 private static final int HASH_SHIFT = 4;
52 // attributes
53 // ------------------------------------------------------------------------
54 private final UnaryPredicate<? super A> ifPred;
55 private final UnaryFunction<? super A, ? extends T> thenFunc;
56 private final UnaryFunction<? super A, ? extends T> elseFunc;
57
58 // constructor
59 // ------------------------------------------------------------------------
60 /**
61 * Create a new ConditionalUnaryFunction.
62 * @param ifPred if
63 * @param thenFunc then
64 * @param elseFunc else
65 */
66 public ConditionalUnaryFunction(UnaryPredicate<? super A> ifPred, UnaryFunction<? super A, ? extends T> thenFunc,
67 UnaryFunction<? super A, ? extends T> elseFunc) {
68 if (ifPred == null) {
69 throw new IllegalArgumentException("UnaryPredicate argument was null");
70 }
71 this.ifPred = ifPred;
72 if (thenFunc == null || elseFunc == null) {
73 throw new IllegalArgumentException("One or more UnaryFunction arguments was null");
74 }
75 this.thenFunc = thenFunc;
76 this.elseFunc = elseFunc;
77 }
78
79 // predicate interface
80 // ------------------------------------------------------------------------
81 /**
82 * {@inheritDoc}
83 */
84 public T evaluate(A obj) {
85 if (ifPred.test(obj)) {
86 return thenFunc.evaluate(obj);
87 } else {
88 return elseFunc.evaluate(obj);
89 }
90 }
91
92 /**
93 * {@inheritDoc}
94 */
95 public boolean equals(Object that) {
96 return that == this || (that instanceof ConditionalUnaryFunction<?, ?>
97 && equals((ConditionalUnaryFunction<?, ?>) that));
98 }
99
100 /**
101 * Learn whether another ConditionalUnaryFunction is equal to this.
102 * @param that ConditionalUnaryFunction to test
103 * @return boolean
104 */
105 public boolean equals(ConditionalUnaryFunction<?, ?> that) {
106 return null != that
107 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
108 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc))
109 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc));
110 }
111
112 /**
113 * {@inheritDoc}
114 */
115 public int hashCode() {
116 int hash = "ConditionalUnaryFunction".hashCode();
117 if (null != ifPred) {
118 hash <<= HASH_SHIFT;
119 hash ^= ifPred.hashCode();
120 }
121 if (null != thenFunc) {
122 hash <<= HASH_SHIFT;
123 hash ^= thenFunc.hashCode();
124 }
125 if (null != elseFunc) {
126 hash <<= HASH_SHIFT;
127 hash ^= elseFunc.hashCode();
128 }
129 return hash;
130 }
131
132 /**
133 * {@inheritDoc}
134 */
135 public String toString() {
136 return "ConditionalUnaryFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";
137 }
138
139 }