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Commons Collections example source code file (EnumerationIterator.java)

This example Commons Collections source code file (EnumerationIterator.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

collection, collection, enumeration, enumeration, enumerationiterator, enumerationiterator, illegalstateexception, iterator, no, object, object, unsupportedoperationexception, util

The Commons Collections EnumerationIterator.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.Collection;
import java.util.Enumeration;
import java.util.Iterator;

/** 
 * Adapter to make {@link Enumeration Enumeration} instances appear
 * to be {@link Iterator Iterator} instances.
 *
 * @since Commons Collections 1.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author <a href="mailto:jstrachan@apache.org">James Strachan
 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall
 */
public class EnumerationIterator implements Iterator {
    
    /** The collection to remove elements from */
    private Collection collection;
    /** The enumeration being converted */
    private Enumeration enumeration;
    /** The last object retrieved */
    private Object last;
    
    // Constructors
    //-----------------------------------------------------------------------
    /**
     * Constructs a new <code>EnumerationIterator that will not
     * function until {@link #setEnumeration(Enumeration)} is called.
     */
    public EnumerationIterator() {
        this(null, null);
    }

    /**
     * Constructs a new <code>EnumerationIterator that provides
     * an iterator view of the given enumeration.
     *
     * @param enumeration  the enumeration to use
     */
    public EnumerationIterator(final Enumeration enumeration) {
        this(enumeration, null);
    }

    /**
     * Constructs a new <code>EnumerationIterator that will remove
     * elements from the specified collection.
     *
     * @param enumeration  the enumeration to use
     * @param collection  the collection to remove elements form
     */
    public EnumerationIterator(final Enumeration enumeration, final Collection collection) {
        super();
        this.enumeration = enumeration;
        this.collection = collection;
        this.last = null;
    }

    // Iterator interface
    //-----------------------------------------------------------------------
    /**
     * Returns true if the underlying enumeration has more elements.
     *
     * @return true if the underlying enumeration has more elements
     * @throws NullPointerException  if the underlying enumeration is null
     */
    public boolean hasNext() {
        return enumeration.hasMoreElements();
    }

    /**
     * Returns the next object from the enumeration.
     *
     * @return the next object from the enumeration
     * @throws NullPointerException if the enumeration is null
     */
    public Object next() {
        last = enumeration.nextElement();
        return last;
    }

    /**
     * Removes the last retrieved element if a collection is attached.
     * <p>
     * Functions if an associated <code>Collection is known.
     * If so, the first occurrence of the last returned object from this
     * iterator will be removed from the collection.
     *
     * @exception IllegalStateException <code>next() not called.
     * @exception UnsupportedOperationException if no associated collection
     */
    public void remove() {
        if (collection != null) {
            if (last != null) {
                collection.remove(last);
            } else {
                throw new IllegalStateException("next() must have been called for remove() to function");
            }
        } else {
            throw new UnsupportedOperationException("No Collection associated with this Iterator");
        }
    }

    // Properties
    //-----------------------------------------------------------------------
    /**
     * Returns the underlying enumeration.
     *
     * @return the underlying enumeration
     */
    public Enumeration getEnumeration() {
        return enumeration;
    }

    /**
     * Sets the underlying enumeration.
     *
     * @param enumeration  the new underlying enumeration
     */
    public void setEnumeration(final Enumeration enumeration) {
        this.enumeration = enumeration;
    }
    
}

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