import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;

class JRadioButtonSample extends JFrame
                         implements ChangeListener {
   JRadioButtonSample() {
      getContentPane().setLayout(new FlowLayout());

      JRadioButton rb1 = new JRadioButton("ON", true);
      JRadioButton rb2 = new JRadioButton("OFF");
      JRadioButton rb3 = new JRadioButton("OFF");
      JRadioButton rb4 = new JRadioButton("OFF");

      rb1.addChangeListener(this);
      rb2.addChangeListener(this);
      rb3.addChangeListener(this);
      rb4.addChangeListener(this);

      getContentPane().add(rb1);
      getContentPane().add(rb2);
      getContentPane().add(rb3);
      getContentPane().add(rb4);

      ButtonGroup bg = new ButtonGroup();
      bg.add(rb1);
      bg.add(rb2);
      bg.add(rb3);
      bg.add(rb4);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setTitle("JRadioButtonを使ってラジオボタンを表示");
      setSize(530, 100);
      setVisible(true);
   }
   public void stateChanged(ChangeEvent e) {
      JRadioButton cb = (JRadioButton)e.getSource();
      if (cb.isSelected()) {
         cb.setText("ON");
      } else {
         cb.setText("OFF");
      }
   }
   public static void main(String[] args) {
      new JRadioButtonSample();
   }
}