import java.util.Vector;
import java.awt.Point;

/*
By Futrelle for COM1370 6/30/01
A stack of Point objects.
Done according to API for Java 1.1;
*/

/**
 * Is a stack that holds Point objects.<br>
 * Includes push(), pop() and empty().
 * @version  1.0 June 30, 2001.
 * @author R. P. Futrelle for COM1370
 **/

public class PointStack {

    public static void main(String[]  args) {
	PointStack  ps  = new  PointStack();
	System.out.println("pushing Point(1,2)");
	ps.push(new Point(1,2));
	System.out.println("pushing Point(3,4)");
	ps.push(new  Point(3,4));
	Point p;
	p = ps.pop();
	System.out.println("Popping, x and y are: " + p.x +  " " +  p.y);
	p = ps.pop();
	System.out.println("Popping, x and y are: " + p.x +  " " +  p.y);
	System.out.println("Should  empty (true) and  null now: "
	+ ps.empty() + " " + ps.pop());
    } // main()
		
    private Vector stack;

    PointStack() {
	stack  = new Vector();
    }

    /**
     * True initially or if all  added  items have been popped.
     */
    public boolean empty() {
	return (stack.size() == 0);
    }

    /**
     * Adds  a Point  to the top  of the stack.
     */
    public void push(Point  p){
	stack.addElement(p);
    }

    /**
     * Removes and returns the Point  on  the top  of the  stack,
     * or null if the stack is empty.
     */
     public Point pop() {
	if(stack.size() == 0)
	    return null;
	Point p  = (Point) stack.lastElement();
	stack.removeElementAt(stack.size() - 1);
	return p;
    }

}