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Commons Collections example source code file (TransformIterator.java)

This example Commons Collections source code file (TransformIterator.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

iterator, iterator, object, object, transformer, transformer, transformiterator, transformiterator, util

The Commons Collections TransformIterator.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.iterators;

import java.util.Iterator;

import org.apache.commons.collections.Transformer;

/** 
 * Decorates an iterator such that each element returned is transformed.
 *
 * @since Commons Collections 1.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author James Strachan
 * @author Stephen Colebourne
 */
public class TransformIterator implements Iterator {

    /** The iterator being used */
    private Iterator iterator;
    /** The transformer being used */
    private Transformer transformer;

    //-----------------------------------------------------------------------
    /**
     * Constructs a new <code>TransformIterator that will not function
     * until the {@link #setIterator(Iterator) setIterator} method is 
     * invoked.
     */
    public TransformIterator() {
        super();
    }

    /**
     * Constructs a new <code>TransformIterator that won't transform
     * elements from the given iterator.
     *
     * @param iterator  the iterator to use
     */
    public TransformIterator(Iterator iterator) {
        super();
        this.iterator = iterator;
    }

    /**
     * Constructs a new <code>TransformIterator that will use the
     * given iterator and transformer.  If the given transformer is null,
     * then objects will not be transformed.
     *
     * @param iterator  the iterator to use
     * @param transformer  the transformer to use
     */
    public TransformIterator(Iterator iterator, Transformer transformer) {
        super();
        this.iterator = iterator;
        this.transformer = transformer;
    }

    //-----------------------------------------------------------------------
    public boolean hasNext() {
        return iterator.hasNext();
    }

    /**
     * Gets the next object from the iteration, transforming it using the
     * current transformer. If the transformer is null, no transformation
     * occurs and the object from the iterator is returned directly.
     * 
     * @return the next object
     * @throws java.util.NoSuchElementException if there are no more elements
     */
    public Object next() {
        return transform(iterator.next());
    }

    public void remove() {
        iterator.remove();
    }

    //-----------------------------------------------------------------------
    /** 
     * Gets the iterator this iterator is using.
     * 
     * @return the iterator.
     */
    public Iterator getIterator() {
        return iterator;
    }

    /** 
     * Sets the iterator for this iterator to use.
     * If iteration has started, this effectively resets the iterator.
     * 
     * @param iterator  the iterator to use
     */
    public void setIterator(Iterator iterator) {
        this.iterator = iterator;
    }

    //-----------------------------------------------------------------------
    /** 
     * Gets the transformer this iterator is using.
     * 
     * @return the transformer.
     */
    public Transformer getTransformer() {
        return transformer;
    }

    /** 
     * Sets the transformer this the iterator to use.
     * A null transformer is a no-op transformer.
     * 
     * @param transformer  the transformer to use
     */
    public void setTransformer(Transformer transformer) {
        this.transformer = transformer;
    }

    //-----------------------------------------------------------------------
    /**
     * Transforms the given object using the transformer.
     * If the transformer is null, the original object is returned as-is.
     *
     * @param source  the object to transform
     * @return the transformed object
     */
    protected Object transform(Object source) {
        if (transformer != null) {
            return transformer.transform(source);
        }
        return source;
    }
}

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