public class Stack<T> implements Worklist<T> {
  private Node<T> top = null;
  public void add(T data) {
    top = new Node<T>(data,top);
  }
  public boolean hasMore() {
    return (top != null);
  }
  public T remove() {
    Node<T> n = top;
    top = n.getLink();
    return n.getData();
  }
}