import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Punkter_0 extends JPanel implements MouseListener{
    
    public static void main (String[] arg) {
	JPanel s = new Punkter_0();

	JFrame f = new JFrame();
	f.add(s);
	f.setVisible(true);
	f.setBounds(100, 100, 400, 400);

	f.setVisible(true);
	f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public Punkter_0 () {
        setBackground( Color.YELLOW );
        addMouseListener(this);
    }

    public void mouseClicked (MouseEvent e) {
	int x = e.getX(); 
	int y = e.getY();

	Graphics g = getGraphics();
	g.setColor(Color.black);
	g.fillOval(x, y, 10, 10);
    }

    public void mouseEntered (MouseEvent e) { }
    public void mouseExited (MouseEvent e) { }

    public void mousePressed (MouseEvent e) { }
    public void mouseReleased (MouseEvent e) { }

}