12. Simulating a Traffic light

a) Write a java program that simulates a traffic light. The program lets the user select one of three lights: red, yellow, or green. When a radio button is selected, the light is turned on, and only one light can be on at a time No light is on when the program starts.

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

class TrafficLight extends JFrame implements ActionListener

{

String msg=" " ;

private JLabel label;

private JTextField display;

private JRadioButton r1,r2,r3;

private ButtonGroup bg;

private Container c;

public TrafficLight()

{

setLayout(new FlowLayout());

c=getContentPane();

label=new JLabel(" Traffic Light");

display =new JTextField(10);

r1=new JRadioButton("RED");

r2=new JRadioButton("GREEN");

r3=new JRadioButton("YELLOW");

bg=new ButtonGroup();

c.add(label);

c.add(r1);

c.add(r2);

c.add(r3);

c.add(display);

bg.add(r1);

bg.add(r2);

bg.add(r3);

r1.addActionListener(this);

r2.addActionListener(this);

r3.addActionListener(this);

setSize(400,400);

setVisible(true);

c.setBackground(Color.pink);

}

public void actionPerformed(ActionEvent ie)

{

msg=ie.getActionCommand();

if (msg.equals("RED"))

{

c.setBackground(Color.RED);

display.setText(msg+ " :TURN ON");

}

else if (msg.equals("GREEN"))

{

c.setBackground(Color.GREEN);

display.setText(msg+ " :TURN ON");

}

else if (msg.equals("YELLOW"))

{

c.setBackground(Color.YELLOW);

display.setText(msg+ " :TURN ON");

}

}

public static void main(String args[])

{

TrafficLight light=new TrafficLight();

light.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}