swing-3-单选框

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

public class test extends JApplet
implements ActionListener{
    JTextField jtf;
    public void init(){
        Container contentPane = getContentPane();
        contentPane.setLayout(new FlowLayout());
    
        JRadioButton b1 = new JRadioButton("A");
        b1.addActionListener(this);
        contentPane.add(b1);
        
        JRadioButton b2 = new JRadioButton("B");
        b2.addActionListener(this);
        contentPane.add(b2);
        
        JRadioButton b3 = new JRadioButton("C");
        b3.addActionListener(this);
        contentPane.add(b3);
        
        ButtonGroup bg = new ButtonGroup();
        bg.add(b1);
        bg.add(b2);
        bg.add(b3);
        
        jtf = new JTextField(15);
        contentPane.add(jtf);
        
    }
    public void actionPerformed(ActionEvent ae){
        jtf.setText(ae.getActionCommand());
    }

}