//  Job: Jay's Own Browser, a web browser written in Java by Jay Skeer
//  Copyright (C) 1996 Jay Skeer, Jay Prime Positive
//
//  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.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//

import EmptyListException;
public class HeaderOneWayLinkedList {
    OneWayLinkedList first= null;
    OneWayLinkedList last= null;
    int size= 0;
    
    public HeaderOneWayLinkedList() {
        first= null;
	last= null;
	size= 0;
    }

    public Object firstItem() throws EmptyListException {
	if (size <= 0) {
	    throw new EmptyListException();
	} else {
	    OneWayLinkedList ll= peekBeg();
	    if (null == ll) {
		throw new EmptyListException();
 	    } else {
		return ll.peekBeg();
	    }
	}
    }

    public OneWayLinkedList peekBeg() {
	return first;
    }

    public OneWayLinkedList peekEnd() {
	return last;
    }

    public int size() {
	return size;
    }

    public void addBeg(OneWayLinkedList item) {
	if (null == last) {
	    last= item;
	}
	if (null != first) {
	    first.addBeg(item);
	}
	first= item;
	size= size + 1;
    }

    public void addEnd(OneWayLinkedList item) {
	if (null == last) {
	    first= item;
	} else {
	    last.addBeg(item);
	}
	last= item;
	size= size + 1;
    }

    public void removeBeg() throws EmptyListException {
	if (null == first) {
	    throw new EmptyListException();
	} else {
	    OneWayLinkedList oe= first;
	    first= oe.next;
	    oe.next= null;
	}
	if (null == first) {
	    last= null;
	}
	size= size - 1;
    }
}