org.apache.commons.collections.collection.TransformedCollection Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections.collection;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.collections.Transformer;
/**
* Decorates another Collection to transform objects that are added.
*
* The add methods are affected by this class.
* Thus objects must be removed or searched for using their transformed form.
* For example, if the transformation converts Strings to Integers, you must
* use the Integer form to remove objects.
*
* This class is Serializable from Commons Collections 3.1.
*
* @since Commons Collections 3.0
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public class TransformedCollection extends AbstractSerializableCollectionDecorator {
/** Serialization version */
private static final long serialVersionUID = 8692300188161871514L;
/** The transformer to use */
protected final Transformer transformer;
/**
* Factory method to create a transforming collection.
*
* If there are any elements already in the collection being decorated, they
* are NOT transformed.
*
* @param coll the collection to decorate, must not be null
* @param transformer the transformer to use for conversion, must not be null
* @return a new transformed collection
* @throws IllegalArgumentException if collection or transformer is null
*/
public static Collection decorate(Collection coll, Transformer transformer) {
return new TransformedCollection(coll, transformer);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* If there are any elements already in the collection being decorated, they
* are NOT transformed.
*
* @param coll the collection to decorate, must not be null
* @param transformer the transformer to use for conversion, must not be null
* @throws IllegalArgumentException if collection or transformer is null
*/
protected TransformedCollection(Collection coll, Transformer transformer) {
super(coll);
if (transformer == null) {
throw new IllegalArgumentException("Transformer must not be null");
}
this.transformer = transformer;
}
/**
* Transforms an object.
*
* The transformer itself may throw an exception if necessary.
*
* @param object the object to transform
* @return a transformed object
*/
protected Object transform(Object object) {
return transformer.transform(object);
}
/**
* Transforms a collection.
*
* The transformer itself may throw an exception if necessary.
*
* @param coll the collection to transform
* @return a transformed object
*/
protected Collection transform(Collection coll) {
List list = new ArrayList(coll.size());
for (Iterator it = coll.iterator(); it.hasNext(); ) {
list.add(transform(it.next()));
}
return list;
}
//-----------------------------------------------------------------------
public boolean add(Object object) {
object = transform(object);
return getCollection().add(object);
}
public boolean addAll(Collection coll) {
coll = transform(coll);
return getCollection().addAll(coll);
}
}