import javax.swing.JComponent;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;

public class TrafficLightComponent extends JComponent
{
   public void paintComponent(Graphics g)
   {
      Graphics2D g2 = (Graphics2D) g;
      g2.setColor(Color.RED);
      g2.fillOval(10, 10, 40, 40);
      g2.setColor(Color.YELLOW);
      g2.fillOval(10, 60, 40, 40);
      g2.setColor(Color.GREEN);
      g2.fillOval(10, 110, 40, 40);
   }
}