Traffic Light Simulation

traffic.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Light extends JPanel implements ActionListener {
	private JRadioButton r1,r2,r3;
	private Color color1,color2,color3,bgcolor;
	Light() {
		setBounds(0, 0, 640, 480);
		
		r1 = new JRadioButton("Red");
		r2 = new JRadioButton("Yellow");
		r3 = new JRadioButton("Green");
		r1.setSelected(true);

		bgcolor = getBackground();
		
		color1 = Color.red;
		color2 = bgcolor;
		color3 = bgcolor;

		ButtonGroup gp = new ButtonGroup();

		gp.add(r1);
		gp.add(r2);
		gp.add(r3);

		add(r1);
		add(r2);
		add(r3);

		r1.addActionListener(this);
		r2.addActionListener(this);
		r3.addActionListener(this);
	}
	public void actionPerformed(ActionEvent e) {
		color1 = bgcolor;
		color2 = bgcolor;
		color3 = bgcolor;
		
			 if(r1.isSelected()) color1 = Color.red;
		else if(r2.isSelected()) color2 = Color.yellow;
		else if(r3.isSelected()) color3 = Color.green;
		
		repaint();
	}

	public void paintComponent(Graphics g) {
		super.paintComponent(g);
				// x    y  cx  cy
		g.drawOval(50,  50, 50, 50);
		g.drawOval(50, 110, 50, 50);
		g.drawOval(50, 170, 50, 50);
		
		g.setColor(color1);
		g.fillOval(50,  50, 50, 50);
		g.setColor(color2);
		g.fillOval(50, 110, 50, 50);
		g.setColor(color3);
		g.fillOval(50, 170, 50, 50);
	}
}

public class traffic {
	public static void main(String args[]) {
		JFrame f = new JFrame();
		f.setSize(640, 480);
		f.setLayout(null);
		f.add(new Light());
		f.setVisible(true);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}