public class DNode<E> implements Position<E>
{
    private DNode<E> prev, next;
    private E element;

    public DNode( DNode<E> newPrev, DNode<E> newNext, E elem )
    {
        prev = newPrev;
        next = newNext;
        element = elem;
    }

    public E element() throws InvalidPositionException
    {
        if ( prev==null && next==null )
            throw new InvalidPositionException(" Position not in the list ");
        return element;
    }

    public DNode<E> getNext() { return next; }
    public DNode<E> getPrev() { return prev; }

    public void setNext( DNode<E> newNext ){ next = newNext; }
    public void setPrev( DNode<E> newPrev ){ prev = newPrev; }
    public void setElement( E newElem ){ element = newElem; }

}