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 }