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.BinaryPredicate;
022 import org.apache.commons.functor.BinaryProcedure;
023 import org.apache.commons.functor.core.NoOp;
024
025 /**
026 * A {@link BinaryProcedure BinaryProcedure}
027 * similiar to Java's "ternary"
028 * or "conditional" operator (<code>? :</code>).
029 * Given a {@link BinaryPredicate predicate}
030 * <i>p</i> and {@link BinaryProcedure procedures}
031 * <i>q</i> and <i>r</i>, {@link #run runs}
032 * <code>if (p.test(x,y)) { q.run(x,y); } else { r.run(x,y); }</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: 1166384 $ $Date: 2011-09-07 22:22:00 +0200 (Wed, 07 Sep 2011) $
042 * @author Rodney Waldhoff
043 */
044 public final class ConditionalBinaryProcedure<L, R> implements BinaryProcedure<L, R>, Serializable {
045
046 /**
047 * serialVersionUID declaration.
048 */
049 private static final long serialVersionUID = -3521992036791188475L;
050
051 /** Base hash integer used to shift hash */
052 private static final int HASH_SHIFT = 4;
053 // attributes
054 // ------------------------------------------------------------------------
055 private final BinaryPredicate<? super L, ? super R> ifPred;
056 private final BinaryProcedure<? super L, ? super R> thenProc;
057 private final BinaryProcedure<? super L, ? super R> elseProc;
058
059 // constructor
060 // ------------------------------------------------------------------------
061
062 /**
063 * Create a new ConditionalBinaryProcedure.
064 * @param ifPred to evaluate
065 * @param thenProc if <code>ifPred</code> yields <code>true</code>
066 */
067 public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
068 BinaryProcedure<? super L, ? super R> thenProc) {
069 this(ifPred, thenProc, NoOp.instance());
070 }
071
072 /**
073 * Create a new ConditionalBinaryProcedure.
074 * @param ifPred to evaluate
075 * @param thenProc if <code>ifPred</code> yields <code>true</code>
076 * @param elseProc if <code>ifPred</code> yields <code>false</code>
077 */
078 public ConditionalBinaryProcedure(BinaryPredicate<? super L, ? super R> ifPred,
079 BinaryProcedure<? super L, ? super R> thenProc, BinaryProcedure<? super L, ? super R> elseProc) {
080 if (ifPred == null) {
081 throw new IllegalArgumentException("BinaryPredicate argument was null");
082 }
083 this.ifPred = ifPred;
084 if (thenProc == null || elseProc == null) {
085 throw new IllegalArgumentException("One or more BinaryProcedure arguments was null");
086 }
087 this.thenProc = thenProc;
088 this.elseProc = elseProc;
089 }
090
091 // predicate interface
092 // ------------------------------------------------------------------------
093
094 /**
095 * {@inheritDoc}
096 */
097 public void run(L left, R right) {
098 if (ifPred.test(left, right)) {
099 thenProc.run(left, right);
100 } else {
101 elseProc.run(left, right);
102 }
103 }
104
105 /**
106 * {@inheritDoc}
107 */
108 public boolean equals(Object that) {
109 return that == this || (that instanceof ConditionalBinaryProcedure<?, ?>
110 && equals((ConditionalBinaryProcedure<?, ?>) that));
111 }
112
113 /**
114 * Learn whether a given ConditionalBinaryProcedure is equal to this.
115 * @param that compared object
116 * @return boolean
117 */
118 public boolean equals(ConditionalBinaryProcedure<?, ?> that) {
119 return null != that
120 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
121 && (null == thenProc ? null == that.thenProc : thenProc.equals(that.thenProc))
122 && (null == elseProc ? null == that.elseProc : elseProc.equals(that.elseProc));
123 }
124
125 /**
126 * {@inheritDoc}
127 */
128 public int hashCode() {
129 int hash = "ConditionalBinaryProcedure".hashCode();
130 if (null != ifPred) {
131 hash <<= HASH_SHIFT;
132 hash ^= ifPred.hashCode();
133 }
134 if (null != thenProc) {
135 hash <<= HASH_SHIFT;
136 hash ^= thenProc.hashCode();
137 }
138 if (null != elseProc) {
139 hash <<= HASH_SHIFT;
140 hash ^= elseProc.hashCode();
141 }
142 return hash;
143 }
144
145 /**
146 * {@inheritDoc}
147 */
148 public String toString() {
149 return "ConditionalBinaryProcedure<" + ifPred + "?" + thenProc + ":" + elseProc + ">";
150 }
151 }