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.Predicate;
22 import org.apache.commons.functor.Procedure;
23 import org.apache.commons.functor.core.NoOp;
24 import org.apache.commons.lang3.Validate;
25
26 /**
27 * A {@link Procedure Procedure}
28 * similiar to Java's "ternary"
29 * or "conditional" operator (<code>? :</code>).
30 * Given a {@link Predicate predicate}
31 * <i>p</i> and {@link Procedure procedures}
32 * <i>q</i> and <i>r</i>, {@link #run runs}
33 * <code>if (p.test()) { q.run(); } else { r.run(); }</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 * @version $Revision: 1365329 $ $Date: 2012-07-24 19:34:23 -0300 (Tue, 24 Jul 2012) $
43 */
44 public final class ConditionalProcedure implements Procedure, Serializable {
45 /**
46 * serialVersionUID declaration.
47 */
48 private static final long serialVersionUID = -4228632798836328605L;
49
50 /** Base hash integer used to shift hash. */
51 private static final int HASH_SHIFT = 4;
52
53 // attributes
54 // ------------------------------------------------------------------------
55 /**
56 * the condition to be evaluated.
57 */
58 private final Predicate ifPred;
59 /**
60 * the procedure executed if the condition is satisfied.
61 */
62 private final Procedure thenProc;
63 /**
64 * the procedure executed if the condition is not satisfied.
65 */
66 private final Procedure elseProc;
67
68 // constructor
69 // ------------------------------------------------------------------------
70 /**
71 * Create a new ConditionalProcedure.
72 * @param ifPred if
73 * @param thenProc then
74 */
75 public ConditionalProcedure(Predicate ifPred, Procedure thenProc) {
76 this(ifPred, thenProc, NoOp.instance());
77 }
78
79 /**
80 * Create a new ConditionalProcedure.
81 * @param ifPred if
82 * @param thenProc then
83 * @param elseProc else
84 */
85 public ConditionalProcedure(Predicate ifPred, Procedure thenProc, Procedure elseProc) {
86 this.ifPred = Validate.notNull(ifPred, "Predicate argument was null");
87 this.thenProc = Validate.notNull(thenProc, "'then' Procedure argument was null");
88 this.elseProc = Validate.notNull(elseProc, "'else' Procedure argument was null");
89 }
90
91 // predicate interface
92 // ------------------------------------------------------------------------
93 /**
94 * {@inheritDoc}
95 */
96 public void run() {
97 if (ifPred.test()) {
98 thenProc.run();
99 } else {
100 elseProc.run();
101 }
102 }
103
104 /**
105 * {@inheritDoc}
106 */
107 @Override
108 public boolean equals(Object that) {
109 return that == this || (that instanceof ConditionalProcedure && equals((ConditionalProcedure) that));
110 }
111
112 /**
113 * Learn whether another ConditionalProcecure is equal to this.
114 * @param that the ConditionalProcedure to test
115 * @return boolean
116 */
117 public boolean equals(ConditionalProcedure that) {
118 return null != that
119 && ifPred.equals(that.ifPred)
120 && thenProc.equals(that.thenProc)
121 && elseProc.equals(that.elseProc);
122 }
123
124 /**
125 * {@inheritDoc}
126 */
127 @Override
128 public int hashCode() {
129 int hash = "ConditionalProcedure".hashCode();
130 hash <<= HASH_SHIFT;
131 hash ^= ifPred.hashCode();
132 hash <<= HASH_SHIFT;
133 hash ^= thenProc.hashCode();
134 hash <<= HASH_SHIFT;
135 hash ^= elseProc.hashCode();
136 return hash;
137 }
138
139 /**
140 * {@inheritDoc}
141 */
142 @Override
143 public String toString() {
144 return "ConditionalProcedure<" + ifPred + "?" + thenProc + ":" + elseProc + ">";
145 }
146
147 }