001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.functor.core.composite;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.Predicate;
022 import org.apache.commons.functor.Procedure;
023 import org.apache.commons.functor.core.NoOp;
024
025 /**
026 * A {@link Procedure Procedure}
027 * similiar to Java's "ternary"
028 * or "conditional" operator (<code>? :</code>).
029 * Given a {@link Predicate predicate}
030 * <i>p</i> and {@link Procedure procedures}
031 * <i>q</i> and <i>r</i>, {@link #run runs}
032 * <code>if (p.test()) { q.run(); } else { r.run(); }</code>.
033 * <p>
034 * Note that although this class implements
035 * {@link Serializable}, a given instance will
036 * only be truly <code>Serializable</code> if all the
037 * underlying functors are. Attempts to serialize
038 * an instance whose delegates are not all
039 * <code>Serializable</code> will result in an exception.
040 * </p>
041 * @version $Revision: 1170777 $ $Date: 2011-09-14 21:13:47 +0200 (Wed, 14 Sep 2011) $
042 * @author Rodney Waldhoff
043 */
044 public final class ConditionalProcedure implements Procedure, Serializable {
045 /**
046 * serialVersionUID declaration.
047 */
048 private static final long serialVersionUID = -4228632798836328605L;
049
050 /** Base hash integer used to shift hash */
051 private static final int HASH_SHIFT = 4;
052
053 // attributes
054 // ------------------------------------------------------------------------
055 private final Predicate ifPred;
056 private final Procedure thenProc;
057 private final Procedure elseProc;
058
059 // constructor
060 // ------------------------------------------------------------------------
061 /**
062 * Create a new ConditionalProcedure.
063 * @param ifPred if
064 * @param thenProc then
065 */
066 public ConditionalProcedure(Predicate ifPred, Procedure thenProc) {
067 this(ifPred, thenProc, NoOp.instance());
068 }
069
070 /**
071 * Create a new ConditionalProcedure.
072 * @param ifPred if
073 * @param thenProc then
074 * @param elseProc else
075 */
076 public ConditionalProcedure(Predicate ifPred, Procedure thenProc, Procedure elseProc) {
077 if (ifPred == null) {
078 throw new IllegalArgumentException("Predicate argument was null");
079 }
080 this.ifPred = ifPred;
081 if (thenProc == null || elseProc == null) {
082 throw new IllegalArgumentException("Procedure argument was null");
083 }
084 this.thenProc = thenProc;
085 this.elseProc = elseProc;
086 }
087
088 // predicate interface
089 // ------------------------------------------------------------------------
090 /**
091 * {@inheritDoc}
092 */
093 public void run() {
094 if (ifPred.test()) {
095 thenProc.run();
096 } else {
097 elseProc.run();
098 }
099 }
100
101 /**
102 * {@inheritDoc}
103 */
104 public boolean equals(Object that) {
105 return that == this || (that instanceof ConditionalProcedure && equals((ConditionalProcedure) that));
106 }
107
108 /**
109 * Learn whether another ConditionalProcecure is equal to this.
110 * @param that the ConditionalProcedure to test
111 * @return boolean
112 */
113 public boolean equals(ConditionalProcedure that) {
114 return null != that
115 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
116 && (null == thenProc ? null == that.thenProc : thenProc.equals(that.thenProc))
117 && (null == elseProc ? null == that.elseProc : elseProc.equals(that.elseProc));
118 }
119
120 /**
121 * {@inheritDoc}
122 */
123 public int hashCode() {
124 int hash = "ConditionalProcedure".hashCode();
125 if (null != ifPred) {
126 hash <<= HASH_SHIFT;
127 hash ^= ifPred.hashCode();
128 }
129 if (null != thenProc) {
130 hash <<= HASH_SHIFT;
131 hash ^= thenProc.hashCode();
132 }
133 if (null != elseProc) {
134 hash <<= HASH_SHIFT;
135 hash ^= elseProc.hashCode();
136 }
137 return hash;
138 }
139
140 /**
141 * {@inheritDoc}
142 */
143 public String toString() {
144 return "ConditionalProcedure<" + ifPred + "?" + thenProc + ":" + elseProc + ">";
145 }
146
147 }