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feilong is a suite of core and expanded libraries that include utility classes, http, excel,cvs, io classes, and much much more.
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/*
 * 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 com.feilong.lib.collection4.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.
 * 
 * @param 
 *
 * @since 1.0
 */
public class EnumerationIterator implements Iterator{

    /** The collection to remove elements from */
    private final Collection collection;

    /** The enumeration being converted */
    private Enumeration    enumeration;

    /** The last object retrieved */
    private E                           last;

    // Constructors
    //-----------------------------------------------------------------------
    /**
     * Constructs a new EnumerationIterator that will not
     * function until {@link #setEnumeration(Enumeration)} is called.
     */
    public EnumerationIterator(){
        this(null, null);
    }

    /**
     * Constructs a new 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 EnumerationIterator that will remove
     * elements from the specified collection.
     *
     * @param enumeration
     *            the enumeration to use
     * @param collection
     *            the collection to remove elements from
     */
    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
     */
    @Override
    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
     */
    @Override
    public E next(){
        last = enumeration.nextElement();
        return last;
    }

    /**
     * Removes the last retrieved element if a collection is attached.
     * 
     * Functions if an associated Collection is known.
     * If so, the first occurrence of the last returned object from this
     * iterator will be removed from the collection.
     *
     * @throws IllegalStateException
     *             next() not called.
     * @throws UnsupportedOperationException
     *             if no associated collection
     */
    @Override
    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;
    }

}