Back to index...

	/*
	* 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.collections4.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 1.0
	*/
	public class EnumerationIterator<E> implements Iterator<E> {

	/** The collection to remove elements from */
	private final Collection<? super E> collection;
	/** The enumeration being converted */
	private Enumeration<? extends E> enumeration;
	/** The last object retrieved */
	private E last;

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

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

	/**
	* Constructs a new <code>EnumerationIterator</code> 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<? extends E> enumeration, final Collection<? super E> 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.
	* <p>
	* Functions if an associated <code>Collection</code> is known.
	* If so, the first occurrence of the last returned object from this
	* iterator will be removed from the collection.
	*
	* @throws IllegalStateException <code>next()</code> 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<? extends E> getEnumeration() {
	return enumeration;
	}

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

	}

Back to index...