Java Swing - Traffic lights

/*

Write a java program that simulates a traffic light . The program lets the  user select one of three lights: red, yellow, or green with radio buttons. On selecting a button, an appropriate message with stop or ready or go should appear above the buttons in a selected color . Initially there is no  message shown .

*/

// Swing components

// Traffic light

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

class TrafficLights implements ActionListener

{

     JFrame jf;

     JRadioButtonMenuItem r1, r2, r3;

     JLabel L1;

    

     TrafficLights()

     {

          jf = new JFrame();

         

          jf.setSize(350,200);

          jf.setTitle("Traffic Lights");

         

          FlowLayout FL = new FlowLayout(FlowLayout.CENTER,20,20);

          jf.setLayout(FL);

         

          Font f1 = new Font("Freestyle Script", Font.BOLD, 30);

          Font f2 = new Font("Freestyle Script", Font.BOLD, 20);

          Dimension d1 = new Dimension(250,50);

          Dimension d2 = new Dimension(75,30);

         

          L1 = new JLabel("",SwingConstants.CENTER);

          L1.setFont(f1);

          L1.setPreferredSize(d1);

                  

          r1 = new JRadioButtonMenuItem("Red");

          r2 = new JRadioButtonMenuItem("Yellow");

          r3 = new JRadioButtonMenuItem("Green");

         

          r1.setFont(f2);

          r2.setFont(f2);

          r3.setFont(f2);

          r1.setPreferredSize(d2);

          r2.setPreferredSize(d2);

          r3.setPreferredSize(d2);

          ButtonGroup bg = new ButtonGroup();

          bg.add(r1);

          bg.add(r2);

          bg.add(r3);

                  

          jf.add(L1);

         

          jf.add(r1);

          jf.add(r2);

          jf.add(r3);

         

          r1.addActionListener(this);

          r2.addActionListener(this);

          r3.addActionListener(this);

             

          jf.setVisible(true);

          jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

     }

    

    

     public void actionPerformed(ActionEvent ae)

     {

          Color c1 = Color.black;

          String str = "";

                  

          if(r1.isSelected())

          {  

              str = "Stop";

              c1 = Color.red;

          }

          if(r2.isSelected())

          {

              str = "Ready";

              c1 = Color.yellow;

          }

          if(r3.isSelected())

          {

              str = "Go";

              c1 = Color.green;

          }

         

             

          L1.setText(str);

          L1.setForeground(c1);   

         

     }

    

     public static void main(String as[])

     {

          new TrafficLights();

     }

}

Output:

Initial window

 

Red Selected

Yellow Selected

Green Selected