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.BinaryProcedure;
23 import org.apache.commons.functor.core.NoOp;
24 import org.apache.commons.lang3.Validate;
25
26 /**
27 * A {@link BinaryProcedure BinaryProcedure}
28 * similiar to Java's "ternary"
29 * or "conditional" operator (<code>? :</code>).
30 * Given a {@link BinaryPredicate predicate}
31 * <i>p</i> and {@link BinaryProcedure procedures}
32 * <i>q</i> and <i>r</i>, {@link #run runs}
33 * <code>if (p.test(x,y)) { q.run(x,y); } else { r.run(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 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
45 */
46 public final class ConditionalBinaryProcedure<L, R> implements BinaryProcedure<L, R>, Serializable {
47
48 /**
49 * serialVersionUID declaration.
50 */
51 private static final long serialVersionUID = -3521992036791188475L;
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 predicate executed if the condition is satisfied.
63 */
64 private final BinaryProcedure<? super L, ? super R> thenProc;
65 /**
66 * the predicate executed if the condition is not satisfied.
67 */
68 private final BinaryProcedure<? super L, ? super R> elseProc;
69
70 // constructor
71 // ------------------------------------------------------------------------
72
73 /**
74 * Create a new ConditionalBinaryProcedure.
75 * @param ifPred to evaluate
76 * @param thenProc if <code>ifPred</code> yields <code>true</code>
77 */
78 public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
79 BinaryProcedure<? super L, ? super R> thenProc) {
80 this(ifPred, thenProc, NoOp.instance());
81 }
82
83 /**
84 * Create a new ConditionalBinaryProcedure.
85 * @param ifPred to evaluate
86 * @param thenProc if <code>ifPred</code> yields <code>true</code>
87 * @param elseProc if <code>ifPred</code> yields <code>false</code>
88 */
89 public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
90 BinaryProcedure<? super L, ? super R> thenProc, BinaryProcedure<? super L, ? super R> elseProc) {
91 this.ifPred = Validate.notNull(ifPred, "BinaryPredicate argument was null");
92 this.thenProc = Validate.notNull(thenProc, "'then' BinaryProcedure argument was null");
93 this.elseProc = Validate.notNull(elseProc, "'else' BinaryProcedure argument was null");
94 }
95
96 // predicate interface
97 // ------------------------------------------------------------------------
98
99 /**
100 * {@inheritDoc}
101 */
102 public void run(L left, R right) {
103 if (ifPred.test(left, right)) {
104 thenProc.run(left, right);
105 } else {
106 elseProc.run(left, right);
107 }
108 }
109
110 /**
111 * {@inheritDoc}
112 */
113 @Override
114 public boolean equals(Object that) {
115 return that == this || (that instanceof ConditionalBinaryProcedure<?, ?>
116 && equals((ConditionalBinaryProcedure<?, ?>) that));
117 }
118
119 /**
120 * Learn whether a given ConditionalBinaryProcedure is equal to this.
121 * @param that compared object
122 * @return boolean
123 */
124 public boolean equals(ConditionalBinaryProcedure<?, ?> that) {
125 return null != that
126 && ifPred.equals(that.ifPred)
127 && thenProc.equals(that.thenProc)
128 && elseProc.equals(that.elseProc);
129 }
130
131 /**
132 * {@inheritDoc}
133 */
134 @Override
135 public int hashCode() {
136 int hash = "ConditionalBinaryProcedure".hashCode();
137 hash <<= HASH_SHIFT;
138 hash ^= ifPred.hashCode();
139 hash <<= HASH_SHIFT;
140 hash ^= thenProc.hashCode();
141 hash <<= HASH_SHIFT;
142 hash ^= elseProc.hashCode();
143 return hash;
144 }
145
146 /**
147 * {@inheritDoc}
148 */
149 @Override
150 public String toString() {
151 return "ConditionalBinaryProcedure<" + ifPred + "?" + thenProc + ":" + elseProc + ">";
152 }
153 }