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
023 /**
024 * A {@link Predicate Predicate}
025 * similiar to Java's "ternary"
026 * or "conditional" operator (<code>? :</code>).
027 * Given three {@link Predicate predicates}
028 * <i>p</i>, <i>q</i>, <i>r</i>,
029 * {@link #test tests}
030 * to
031 * <code>p.test() ? q.test() : r.test()</code>.
032 * <p>
033 * Note that although this class implements
034 * {@link Serializable}, a given instance will
035 * only be truly <code>Serializable</code> if all the
036 * underlying functors are. Attempts to serialize
037 * an instance whose delegates are not all
038 * <code>Serializable</code> will result in an exception.
039 * </p>
040 * @version $Revision: 1166388 $ $Date: 2011-09-07 22:29:02 +0200 (Wed, 07 Sep 2011) $
041 * @author Rodney Waldhoff
042 */
043 public final class ConditionalPredicate implements Predicate, Serializable {
044 /**
045 * serialVersionUID declaration.
046 */
047 private static final long serialVersionUID = 7333505000745854098L;
048
049 /** Base hash integer used to shift hash */
050 private static final int HASH_SHIFT = 4;
051 // attributes
052 // ------------------------------------------------------------------------
053 private final Predicate ifPred;
054 private final Predicate thenPred;
055 private final Predicate elsePred;
056
057 // constructor
058 // ------------------------------------------------------------------------
059 /**
060 * Create a new ConditionalPredicate.
061 * @param ifPred if
062 * @param thenPred then
063 * @param elsePred else
064 */
065 public ConditionalPredicate(Predicate ifPred, Predicate thenPred, Predicate elsePred) {
066 if (ifPred == null || thenPred == null || elsePred == null) {
067 throw new IllegalArgumentException("One or more Predicate arguments was null");
068 }
069 this.ifPred = ifPred;
070 this.thenPred = thenPred;
071 this.elsePred = elsePred;
072 }
073
074 // predicate interface
075 // ------------------------------------------------------------------------
076 /**
077 * {@inheritDoc}
078 */
079 public boolean test() {
080 return ifPred.test() ? thenPred.test() : elsePred.test();
081 }
082
083 /**
084 * {@inheritDoc}
085 */
086 public boolean equals(Object that) {
087 return that == this || (that instanceof ConditionalPredicate && equals((ConditionalPredicate) that));
088 }
089
090 /**
091 * Learn whether another ConditionalPredicate is equal to this.
092 * @param that ConditionalPredicate to test
093 * @return boolean
094 */
095 public boolean equals(ConditionalPredicate that) {
096 return null != that
097 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
098 && (null == thenPred ? null == that.thenPred : thenPred.equals(that.thenPred))
099 && (null == elsePred ? null == that.elsePred : elsePred.equals(that.elsePred));
100 }
101
102 /**
103 * {@inheritDoc}
104 */
105 public int hashCode() {
106 int hash = "ConditionalPredicate".hashCode();
107 if (null != ifPred) {
108 hash <<= HASH_SHIFT;
109 hash ^= ifPred.hashCode();
110 }
111 if (null != thenPred) {
112 hash <<= HASH_SHIFT;
113 hash ^= thenPred.hashCode();
114 }
115 if (null != elsePred) {
116 hash <<= HASH_SHIFT;
117 hash ^= elsePred.hashCode();
118 }
119 return hash;
120 }
121
122 /**
123 * {@inheritDoc}
124 */
125 public String toString() {
126 return "ConditionalPredicate<" + ifPred + "?" + thenPred + ":" + elsePred + ">";
127 }
128
129 }