/**
 * @(#)SublistIterator.java	11/03/05
 * 
 * Copyright 2005 3GP01, KCL.  All unmodified code is copyright of its respective owner.
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * The GNU General Public Licence should be contained within licence.txt;
 * if not, write to the Free Software Foundation, Inc., 51 Franklin Street,
 * Fifth Floor, Boston, MA  02110-1301, USA.
 */

import java.util.*;


public class SublistIterator 
{
	private List l; // list whose sublists are being

	// iterated over
	private int index = 0; // position in l

	// private boolean atEnd = false;
	private List current = new ArrayList();

	private Object head; // head of the list   

	private List sublist = null; // tail of the list 

	private SublistIterator sublistIterator = null;

	public SublistIterator(List ll) 
	{
		l = ll;
		index = 0;
		if (l.size() > 0) {
			current = (List) ((ArrayList) l).clone();
			sublist = (List) ((ArrayList) l).clone();
			head = sublist.get(0);
			sublist.remove(0);
			// atEnd = false; 
			sublistIterator = new SublistIterator(sublist);
		}
	}

	public List getCurrent() 
	{
		return current;
	}

	public boolean atEnd() 
	{
		if (l.size() == 0) 
		{
			return true;
		}
		// if (atEnd) { return true; } 
		return (index == l.size() - 1 && sublistIterator.atEnd());
	}

	public void advance() 
	{
		if (l.size() == 0) {
			return;
		} // can't move
		if (sublistIterator.atEnd()) 
		{
			if (index == l.size() - 1) 
			{
				current = new ArrayList();
				return;
			} // can't move
			index++;
			head = sublist.get(0);
			current = (List) ((ArrayList) sublist).clone();
			sublist.remove(0);
			sublistIterator = new SublistIterator(sublist);
			return;
		}
		sublistIterator.advance();
		List sb = sublistIterator.getCurrent();
		current = (List) ((ArrayList) sb).clone();
		current.add(0, l.get(index));
	}

	public static void main(String[] args) {
		List l = new ArrayList();
		l.add("A");
		l.add("B");
		l.add("a");
		l.add("b");
		l.add("c");
		l.add("d");
		SublistIterator si = new SublistIterator(l);
		do {
			System.out.println(si.getCurrent());
			si.advance();
		} while (!si.atEnd());
	}
}