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.UnaryFunction;
022 import org.apache.commons.functor.UnaryPredicate;
023
024 /**
025 * A {@link UnaryFunction UnaryFunction}
026 * similiar to Java's "ternary"
027 * or "conditional" operator (<code>? :</code>).
028 * Given a {@link UnaryPredicate predicate}
029 * <i>p</i> and {@link UnaryFunction functions}
030 * <i>f</i> and <i>g</i>, {@link #evaluate evalautes}
031 * to
032 * <code>p.test(x) ? f.evaluate(x) : g.evaluate(x)</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: 1170778 $ $Date: 2011-09-14 21:15:01 +0200 (Wed, 14 Sep 2011) $
042 * @author Rodney Waldhoff
043 */
044 public final class ConditionalUnaryFunction<A, T> implements UnaryFunction<A, T>, Serializable {
045 /**
046 * serialVersionUID declaration.
047 */
048 private static final long serialVersionUID = -8152490481969255068L;
049
050 /** Base hash integer used to shift hash */
051 private static final int HASH_SHIFT = 4;
052 // attributes
053 // ------------------------------------------------------------------------
054 private final UnaryPredicate<? super A> ifPred;
055 private final UnaryFunction<? super A, ? extends T> thenFunc;
056 private final UnaryFunction<? super A, ? extends T> elseFunc;
057
058 // constructor
059 // ------------------------------------------------------------------------
060 /**
061 * Create a new ConditionalUnaryFunction.
062 * @param ifPred if
063 * @param thenFunc then
064 * @param elseFunc else
065 */
066 public ConditionalUnaryFunction(UnaryPredicate<? super A> ifPred, UnaryFunction<? super A, ? extends T> thenFunc,
067 UnaryFunction<? super A, ? extends T> elseFunc) {
068 if (ifPred == null) {
069 throw new IllegalArgumentException("UnaryPredicate argument was null");
070 }
071 this.ifPred = ifPred;
072 if (thenFunc == null || elseFunc == null) {
073 throw new IllegalArgumentException("One or more UnaryFunction arguments was null");
074 }
075 this.thenFunc = thenFunc;
076 this.elseFunc = elseFunc;
077 }
078
079 // predicate interface
080 // ------------------------------------------------------------------------
081 /**
082 * {@inheritDoc}
083 */
084 public T evaluate(A obj) {
085 if (ifPred.test(obj)) {
086 return thenFunc.evaluate(obj);
087 } else {
088 return elseFunc.evaluate(obj);
089 }
090 }
091
092 /**
093 * {@inheritDoc}
094 */
095 public boolean equals(Object that) {
096 return that == this || (that instanceof ConditionalUnaryFunction<?, ?>
097 && equals((ConditionalUnaryFunction<?, ?>) that));
098 }
099
100 /**
101 * Learn whether another ConditionalUnaryFunction is equal to this.
102 * @param that ConditionalUnaryFunction to test
103 * @return boolean
104 */
105 public boolean equals(ConditionalUnaryFunction<?, ?> that) {
106 return null != that
107 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred))
108 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc))
109 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc));
110 }
111
112 /**
113 * {@inheritDoc}
114 */
115 public int hashCode() {
116 int hash = "ConditionalUnaryFunction".hashCode();
117 if (null != ifPred) {
118 hash <<= HASH_SHIFT;
119 hash ^= ifPred.hashCode();
120 }
121 if (null != thenFunc) {
122 hash <<= HASH_SHIFT;
123 hash ^= thenFunc.hashCode();
124 }
125 if (null != elseFunc) {
126 hash <<= HASH_SHIFT;
127 hash ^= elseFunc.hashCode();
128 }
129 return hash;
130 }
131
132 /**
133 * {@inheritDoc}
134 */
135 public String toString() {
136 return "ConditionalUnaryFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">";
137 }
138
139 }