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.Function;
22 import org.apache.commons.functor.Predicate;
23
24 /**
25 * A {@link Function Function}
26 * similiar to Java's "ternary"
27 * or "conditional" operator (<code>? :</code>).
28 * Given a {@link Predicate predicate}
29 * <i>p</i> and {@link Function functions}
30 * <i>f</i> and <i>g</i>, {@link #evaluate evaluates}
31 * to
32 * <code>p.test() ? f.evaluate() : g.evaluate()</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: 1166386 $ $Date: 2011-09-07 22:28:01 +0200 (Wed, 07 Sep 2011) $
42 * @author Rodney Waldhoff
43 */
44 public final class ConditionalFunction<T> implements Function<T>, Serializable {
45 /**
46 * serialVersionUID declaration.
47 */
48 private static final long serialVersionUID = 4214871352184887792L;
49
50 /** Base hash integer used to shift hash */
51 private static final int HASH_SHIFT = 4;
52 // attributes
53 // ------------------------------------------------------------------------
54 private final Predicate ifPred;
55 private final Function<? extends T> thenFunc;
56 private final Function<? extends T> elseFunc;
57
58 // constructor
59 // ------------------------------------------------------------------------
60 /**
61 * Create a new ConditionalFunction.
62 * @param ifPred if
63 * @param thenFunc then
64 * @param elseFunc else
65 */
66 public ConditionalFunction(Predicate ifPred, Function<? extends T> thenFunc, Function<? extends T> elseFunc) {
67 if (ifPred == null) {
68 throw new IllegalArgumentException("Predicate argument was null");
69 }
70 this.ifPred = ifPred;
71 if (thenFunc == null || elseFunc == null) {
72 throw new IllegalArgumentException("One or more Function arguments was null");
73 }
74 this.thenFunc = thenFunc;
75 this.elseFunc = elseFunc;
76 }
77
78 // predicate interface
79 // ------------------------------------------------------------------------
80 /**
81 * {@inheritDoc}
82 */
83 public T evaluate() {
84 if (ifPred.test()) {
85 return thenFunc.evaluate();
86 } else {
87 return elseFunc.evaluate();
88 }
89 }
90
91 /**
92 * {@inheritDoc}
93 */
94 public boolean equals(Object that) {
95 return that == this || (that instanceof ConditionalFunction<?> && equals((ConditionalFunction<?>) that));
96 }
97
98 /**
99 * Learn whether another ConditionalFunction is equal to this.
100 * @param that ConditionalFunction to test
101 * @return boolean
102 */
103 public boolean equals(ConditionalFunction<?> that) {
104 return null != that
105 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
106 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc))
107 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc));
108 }
109
110 /**
111 * {@inheritDoc}
112 */
113 public int hashCode() {
114 int hash = "ConditionalFunction".hashCode();
115 if (null != ifPred) {
116 hash <<= HASH_SHIFT;
117 hash ^= ifPred.hashCode();
118 }
119 if (null != thenFunc) {
120 hash <<= HASH_SHIFT;
121 hash ^= thenFunc.hashCode();
122 }
123 if (null != elseFunc) {
124 hash <<= HASH_SHIFT;
125 hash ^= elseFunc.hashCode();
126 }
127 return hash;
128 }
129
130 /**
131 * {@inheritDoc}
132 */
133 public String toString() {
134 return "ConditionalFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";
135 }
136
137 }