Java JRadioButton handle click event

// Demonstrate JRadioButton 
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;

class Demo extends JPanel implements ActionListener {
   JLabel jlab;//from  w  w w  . ja  v a 2  s. c  o  m

   Demo() {
      // Change to flow layout.
      setLayout(new FlowLayout());

      // Create radio buttons and add them to content pane.
      JRadioButton b1 = new JRadioButton("A");
      b1.addActionListener(this);
      add(b1);

      JRadioButton b2 = new JRadioButton("B");
      b2.addActionListener(this);
      add(b2);

      JRadioButton b3 = new JRadioButton("C");
      b3.addActionListener(this);
      add(b3);

      // Define a button group.
      ButtonGroup bg = new ButtonGroup();
      bg.add(b1);
      bg.add(b2);
      bg.add(b3);

      // Create a label and add it to the content pane.
      jlab = new JLabel("Select One");
      add(jlab);
   }

   // Handle button selection.
   public void actionPerformed(ActionEvent ae) {
      jlab.setText("You selected " + ae.getActionCommand());
   }
}

public class Main {
   public static void main(String[] args) {
      Demo panel = new Demo();

      JFrame application = new JFrame();

      application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      application.add(panel);
      application.setSize(250, 250);
      application.setVisible(true);
   }
}