import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;

public class CircleListener extends MouseAdapter {
  private int radius = 25;

  public void mousePressed(MouseEvent event) {
    Applet app = (Applet)event.getSource();
    Graphics g = app.getGraphics();
    g.setColor(Color.blue);
    g.fillOval(event.getX()-radius,
               event.getY()-radius,
               2*radius,
               2*radius);
  }
}