Mouse Event using Java Applet

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


//<applet code="Demo.class" width=200 height=300></applet>
public class Demo extends Applet
{
    int x, y;
    public void init()
    {
        add a = new add();
        addMouseListener(a);
    }
    public void paint(Graphics g)
    {
        g.fillOval(x, y, 20, 20);
    }
    class add implements MouseListener
    {
        public void mouseClicked(MouseEvent e) {}
        public void mouseEntered(MouseEvent e)
        {
            x = e.getX();
            y = e.getY();
            repaint();
        }
        public void mouseReleased(MouseEvent e) {}
        public void mousePressed(MouseEvent e) {}
        public void mouseExited(MouseEvent e) {}
    }
}