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.Function; 022 import org.apache.commons.functor.Predicate; 023 024 /** 025 * A {@link Function Function} 026 * similiar to Java's "ternary" 027 * or "conditional" operator (<code>? :</code>). 028 * Given a {@link Predicate predicate} 029 * <i>p</i> and {@link Function functions} 030 * <i>f</i> and <i>g</i>, {@link #evaluate evaluates} 031 * to 032 * <code>p.test() ? f.evaluate() : g.evaluate()</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: 1166386 $ $Date: 2011-09-07 22:28:01 +0200 (Wed, 07 Sep 2011) $ 042 * @author Rodney Waldhoff 043 */ 044 public final class ConditionalFunction<T> implements Function<T>, Serializable { 045 /** 046 * serialVersionUID declaration. 047 */ 048 private static final long serialVersionUID = 4214871352184887792L; 049 050 /** Base hash integer used to shift hash */ 051 private static final int HASH_SHIFT = 4; 052 // attributes 053 // ------------------------------------------------------------------------ 054 private final Predicate ifPred; 055 private final Function<? extends T> thenFunc; 056 private final Function<? extends T> elseFunc; 057 058 // constructor 059 // ------------------------------------------------------------------------ 060 /** 061 * Create a new ConditionalFunction. 062 * @param ifPred if 063 * @param thenFunc then 064 * @param elseFunc else 065 */ 066 public ConditionalFunction(Predicate ifPred, Function<? extends T> thenFunc, Function<? extends T> elseFunc) { 067 if (ifPred == null) { 068 throw new IllegalArgumentException("Predicate argument was null"); 069 } 070 this.ifPred = ifPred; 071 if (thenFunc == null || elseFunc == null) { 072 throw new IllegalArgumentException("One or more Function arguments was null"); 073 } 074 this.thenFunc = thenFunc; 075 this.elseFunc = elseFunc; 076 } 077 078 // predicate interface 079 // ------------------------------------------------------------------------ 080 /** 081 * {@inheritDoc} 082 */ 083 public T evaluate() { 084 if (ifPred.test()) { 085 return thenFunc.evaluate(); 086 } else { 087 return elseFunc.evaluate(); 088 } 089 } 090 091 /** 092 * {@inheritDoc} 093 */ 094 public boolean equals(Object that) { 095 return that == this || (that instanceof ConditionalFunction<?> && equals((ConditionalFunction<?>) that)); 096 } 097 098 /** 099 * Learn whether another ConditionalFunction is equal to this. 100 * @param that ConditionalFunction to test 101 * @return boolean 102 */ 103 public boolean equals(ConditionalFunction<?> that) { 104 return null != that 105 && (null == ifPred ? null == that.ifPred : ifPred.equals(that.ifPred)) 106 && (null == thenFunc ? null == that.thenFunc : thenFunc.equals(that.thenFunc)) 107 && (null == elseFunc ? null == that.elseFunc : elseFunc.equals(that.elseFunc)); 108 } 109 110 /** 111 * {@inheritDoc} 112 */ 113 public int hashCode() { 114 int hash = "ConditionalFunction".hashCode(); 115 if (null != ifPred) { 116 hash <<= HASH_SHIFT; 117 hash ^= ifPred.hashCode(); 118 } 119 if (null != thenFunc) { 120 hash <<= HASH_SHIFT; 121 hash ^= thenFunc.hashCode(); 122 } 123 if (null != elseFunc) { 124 hash <<= HASH_SHIFT; 125 hash ^= elseFunc.hashCode(); 126 } 127 return hash; 128 } 129 130 /** 131 * {@inheritDoc} 132 */ 133 public String toString() { 134 return "ConditionalFunction<" + ifPred + "?" + thenFunc + ":" + elseFunc + ">"; 135 } 136 137 }