import java.applet.Applet;
import java.awt.Button;
import java.awt.Graphics;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class BotonApplet extends Applet implements ActionListener {
     private Button elBoton;
     private boolean dibujar=false;
     public void init()  {
         elBoton = new Button("Boton");
         super.add(elBoton);
         elBoton.addActionListener(this );
     }
    public void actionPerformed(ActionEvent elEvento) {
       dibujar = true;
       repaint();
    }
    public void paint(Graphics g) {
       if (dibujar) {
        g.fillOval(160,200,50,80);
       }
    }
}