java之swing单选框用法实例分析

import java.awt.*;import javax.swing.*;import java.awt.event.*;public class test extends JAppletimplements 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());  }}