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/*
 *  Copyright (C) 2012 Ed Schaller 
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package net.darkmist.alib.collection;

import java.util.Enumeration;
import java.util.NoSuchElementException;
import java.util.Iterator;

public final class Enumerations
{
	private Enumerations()
	{
	}

	private static final class EmptyEnumeration implements Enumeration
	{
		@SuppressWarnings("rawtypes")
		private static EmptyEnumeration SINGLETON = new EmptyEnumeration();

		private EmptyEnumeration()
		{
		}

		@SuppressWarnings("unchecked")
		static  EmptyEnumeration instance()
		{
			return SINGLETON;
		}

		@Override
		public boolean hasMoreElements()
		{
			return false;
		}

		@Override
		public T nextElement()
		{
			throw new NoSuchElementException("This enumeration is empty");
		}
	}

	public static  Enumeration getEmptyEnumeration()
	{
		return EmptyEnumeration.instance();
	}

	private static final class EnumerationIterator extends NonRemovingIterator
	{
		private Enumeration e;

		/**
		 * @param e The enumeration to back the iterator with.
		 * @throws NullPointerException if e is null
		 */
		public EnumerationIterator(Enumeration e)
		{
			if(e == null)
				throw new NullPointerException("Backing enumeration cannot be null");
			this.e = e;
		}

		@Override
		public boolean hasNext()
		{
			return e.hasMoreElements();
		}

		@Override
		public T next()
		{
			return e.nextElement();
		}
	}

	public static  Iterator asIterator(Enumeration e)
	{
		if(e == null || !e.hasMoreElements())
			return Iterators.getEmptyIterator();
		return new EnumerationIterator(e);
	}
}