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Commons Collections example source code file (TransformedCollection.java)

This example Commons Collections source code file (TransformedCollection.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

abstractserializablecollectiondecorator, collection, collection, illegalargumentexception, iterator, list, object, object, transformedcollection, transformedcollection, transformer, transformer, util

The Commons Collections TransformedCollection.java source code

/*
 *  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 <code>Collection to transform objects that are added.
 * <p>
 * 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.
 * <p>
 * This class is Serializable from Commons Collections 3.1.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (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.
     * <p>
     * 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).
     * <p>
     * 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.
     * <p>
     * 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.
     * <p>
     * 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);
    }

}

Other Commons Collections examples (source code examples)

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