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 }