/*
* Copyright 1999-2004 The Apache Software Foundation
*
* Licensed 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: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
*
* @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
* @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
*/
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</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 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 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</code> 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()</code> 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;
}
}