swing 单选（互斥）按钮

package org.moon.admin;

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.JRadioButton;

public class JRadioButtonTest {
  
    // 视图组件初始化
    private static JFrame f = new JFrame();
    private static ButtonGroup bg = new ButtonGroup();
    private static JRadioButton yes = new JRadioButton("YES");
    private static JRadioButton no = new JRadioButton("NO");
  
    public static void main(String[] args) {
      
        // 同一按钮组的各个JRadioButton是具有互斥性的
        bg.add(yes);
        bg.add(no);
        //建立内部类  实现点击事件
        class Listener implements ActionListener {
            public void actionPerformed(ActionEvent e) {
                String selected = null;
                if (yes.isSelected()) {
                    selected = "yes";
                } else if (no.isSelected()) {
                    selected = "no";
                }
              
                System.out.println(selected);
            }
        }
      
        yes.addActionListener(new Listener());
        no.addActionListener(new Listener());
      
        // 界面上看不到ButtonGroup的踪迹
        f.setLayout(new FlowLayout());
        f.getContentPane().add(yes);
        f.getContentPane().add(no);
      
        // 显示界面
        f.setVisible(true);
    }
}