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.collections.collection; 018 019 import java.util.ArrayList; 020 import java.util.Collection; 021 import java.util.Iterator; 022 import java.util.List; 023 024 import org.apache.commons.collections.Transformer; 025 026 /** 027 * Decorates another <code>Collection</code> to transform objects that are added. 028 * <p> 029 * The add methods are affected by this class. 030 * Thus objects must be removed or searched for using their transformed form. 031 * For example, if the transformation converts Strings to Integers, you must 032 * use the Integer form to remove objects. 033 * <p> 034 * This class is Serializable from Commons Collections 3.1. 035 * 036 * @since Commons Collections 3.0 037 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 038 * 039 * @author Stephen Colebourne 040 */ 041 public class TransformedCollection extends AbstractSerializableCollectionDecorator { 042 043 /** Serialization version */ 044 private static final long serialVersionUID = 8692300188161871514L; 045 046 /** The transformer to use */ 047 protected final Transformer transformer; 048 049 /** 050 * Factory method to create a transforming collection. 051 * <p> 052 * If there are any elements already in the collection being decorated, they 053 * are NOT transformed. 054 * 055 * @param coll the collection to decorate, must not be null 056 * @param transformer the transformer to use for conversion, must not be null 057 * @return a new transformed collection 058 * @throws IllegalArgumentException if collection or transformer is null 059 */ 060 public static Collection decorate(Collection coll, Transformer transformer) { 061 return new TransformedCollection(coll, transformer); 062 } 063 064 //----------------------------------------------------------------------- 065 /** 066 * Constructor that wraps (not copies). 067 * <p> 068 * If there are any elements already in the collection being decorated, they 069 * are NOT transformed. 070 * 071 * @param coll the collection to decorate, must not be null 072 * @param transformer the transformer to use for conversion, must not be null 073 * @throws IllegalArgumentException if collection or transformer is null 074 */ 075 protected TransformedCollection(Collection coll, Transformer transformer) { 076 super(coll); 077 if (transformer == null) { 078 throw new IllegalArgumentException("Transformer must not be null"); 079 } 080 this.transformer = transformer; 081 } 082 083 /** 084 * Transforms an object. 085 * <p> 086 * The transformer itself may throw an exception if necessary. 087 * 088 * @param object the object to transform 089 * @return a transformed object 090 */ 091 protected Object transform(Object object) { 092 return transformer.transform(object); 093 } 094 095 /** 096 * Transforms a collection. 097 * <p> 098 * The transformer itself may throw an exception if necessary. 099 * 100 * @param coll the collection to transform 101 * @return a transformed object 102 */ 103 protected Collection transform(Collection coll) { 104 List list = new ArrayList(coll.size()); 105 for (Iterator it = coll.iterator(); it.hasNext(); ) { 106 list.add(transform(it.next())); 107 } 108 return list; 109 } 110 111 //----------------------------------------------------------------------- 112 public boolean add(Object object) { 113 object = transform(object); 114 return getCollection().add(object); 115 } 116 117 public boolean addAll(Collection coll) { 118 coll = transform(coll); 119 return getCollection().addAll(coll); 120 } 121 122 }