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.algorithm; 018 019 import java.io.Serializable; 020 import java.util.NoSuchElementException; 021 022 import org.apache.commons.functor.BinaryFunction; 023 import org.apache.commons.functor.UnaryPredicate; 024 import org.apache.commons.functor.UnaryProcedure; 025 import org.apache.commons.functor.generator.Generator; 026 027 /** 028 * Return the first Object in a {@link Generator} matching a {@link UnaryPredicate}. 029 * 030 * @param <E> the arguments type. 031 * @version $Revision: 1160622 $ $Date: 2011-08-23 13:03:37 +0200 (Tue, 23 Aug 2011) $ 032 */ 033 public final class FindWithinGenerator<E> 034 implements BinaryFunction<Generator<? extends E>, UnaryPredicate<? super E>, E>, Serializable { 035 036 /** 037 * Basic instance. 038 */ 039 public static final FindWithinGenerator<Object> INSTANCE = new FindWithinGenerator<Object>(); 040 041 /** 042 * serialVersionUID declaration. 043 */ 044 private static final long serialVersionUID = -2824239991638326134L; 045 046 /** 047 * Helper procedure. 048 * 049 * @param <T> the argument type. 050 */ 051 private static class FindProcedure<T> implements UnaryProcedure<T> { 052 /** 053 * The object found, if any. 054 */ 055 private T found; 056 /** 057 * Flag to mark an object has been found. 058 */ 059 private boolean wasFound; 060 /** 061 * The adapted predicate. 062 */ 063 private UnaryPredicate<? super T> pred; 064 065 /** 066 * Create a new FindProcedure. 067 * @param pred the adapted predicate. 068 */ 069 public FindProcedure(UnaryPredicate<? super T> pred) { 070 this.pred = pred; 071 } 072 073 /** 074 * {@inheritDoc} 075 */ 076 public void run(T obj) { 077 if (!wasFound && pred.test(obj)) { 078 wasFound = true; 079 found = obj; 080 } 081 } 082 } 083 084 /** 085 * Flag to mark the {@link FindWithinGenerator#evaluate(Generator, UnaryPredicate)} method must return a user 086 * defined object when the adapted procedure does not find any object. 087 */ 088 private final boolean useIfNone; 089 /** 090 * Object to be returned in the case the adapted procedure does not find any object. 091 */ 092 private final E ifNone; 093 094 /** 095 * Create a new FindWithinGenerator. 096 */ 097 public FindWithinGenerator() { 098 super(); 099 ifNone = null; 100 useIfNone = false; 101 } 102 103 /** 104 * Create a new FindWithinGenerator. 105 * @param ifNone object to return if the Generator contains no matches. 106 */ 107 public FindWithinGenerator(E ifNone) { 108 super(); 109 this.ifNone = ifNone; 110 useIfNone = true; 111 } 112 113 /** 114 * {@inheritDoc} 115 * @param left Generator 116 * @param right UnaryPredicate 117 */ 118 public E evaluate(Generator<? extends E> left, UnaryPredicate<? super E> right) { 119 FindProcedure<E> findProcedure = new FindProcedure<E>(right); 120 left.run(findProcedure); 121 if (!findProcedure.wasFound) { 122 if (useIfNone) { 123 return ifNone; 124 } 125 throw new NoSuchElementException("No element matching " + right + " was found."); 126 } 127 return findProcedure.found; 128 } 129 130 /** 131 * {@inheritDoc} 132 */ 133 public boolean equals(Object obj) { 134 if (obj == this) { 135 return true; 136 } 137 if (!(obj instanceof FindWithinGenerator<?>)) { 138 return false; 139 } 140 FindWithinGenerator<?> other = (FindWithinGenerator<?>) obj; 141 return other.useIfNone == useIfNone && !useIfNone 142 || (other.ifNone == this.ifNone || other.ifNone != null && other.ifNone.equals(this.ifNone)); 143 } 144 145 /** 146 * {@inheritDoc} 147 */ 148 public int hashCode() { 149 if (!this.useIfNone) { 150 return System.identityHashCode(INSTANCE); 151 } 152 int result = "FindWithinGenerator".hashCode(); 153 result ^= this.ifNone == null ? 0 : this.ifNone.hashCode(); 154 return result; 155 } 156 157 /** 158 * Get a static {@link FindWithinGenerator} instance. 159 * @return {@link FindWithinGenerator} 160 */ 161 public static FindWithinGenerator<Object> instance() { 162 return INSTANCE; 163 } 164 }