import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import javax.swing.JComponent;
import javax.swing.JFrame;
 
public class Court extends JFrame implements Runnable {
 
    private int x = 10;
    private int y = 20;
    private int r = 3;
 
    public Court() {
        setBounds(0, 0, 200, 200);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setBackground(Color.BLACK);
 
        // adding the new component here
        getContentPane().add(new CanvasComponent());
 
        this.setVisible(true);
        start();
 
    }
 
    // Custom component for your paint work.
    // JPanel is also a good candidate for this.
    class CanvasComponent extends JComponent {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            g.setColor(Color.BLACK);
            g.fillRect(0, 0, getWidth(), getHeight());
            g.setColor(Color.GREEN);
            g.fillOval(x - r, y - r, 2 * r, 2 * r);
        }
    }
 
    public void run() {
        while (true) {
            x++;
            repaint();
 
            try {
                Thread.sleep(10);
            } catch (InterruptedException ex) {}
        }
    }
 
    public void start() {
        Thread thread = new Thread(this);
        thread.start();
    }
 
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Court();
            }
        });
    }
}//end