Java 入门图形用户界面设计之单选按钮

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

class MyRadio{
    private JFrame frame = new JFrame("一");
    private Container cont = frame.getContentPane();
    private JRadioButton jrb1 = new JRadioButton("1");
    private JRadioButton jrb2 = new JRadioButton("2");
    private JRadioButton jrb3 = new JRadioButton("3");
    private JPanel pan = new JPanel();
    public MyRadio(){
        pan.setBorder(BorderFactory.createTitledBorder("请选择"));
        pan.setLayout(new GridLayout(1,3));
        pan.add(this.jrb1);
        pan.add(this.jrb2);
        pan.add(this.jrb3);
        ButtonGroup group = new ButtonGroup();
        group.add(this.jrb1);
        group.add(this.jrb2);
        group.add(this.jrb3);
        cont.add(pan);
        this.frame.setSize(330,80);
        this.frame.setVisible(true);
        this.frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                super.windowClosing(e);
                System.exit(1);
            }
        });
    }
}
public class Hello {
    public static void main(String[] args) {
        new MyRadio();
    }
}

ButtonGroup group = new ButtonGroup();
group.add(this.jrb1);
group.add(this.jrb2);
group.add(this.jrb3);

import javax.swing.*;
import java.awt.*;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

class MyRadio implements ItemListener{
    private JLabel a = new JLabel("选中");
    private JLabel b = new JLabel("未选中");
    private JFrame frame = new JFrame("一");
    private Container cont = frame.getContentPane();
    private JRadioButton jrb1 = new JRadioButton("A",true);
    private JRadioButton jrb2 = new JRadioButton("B",true);
    private JPanel pan = new JPanel();
    public MyRadio(){
        ButtonGroup group = new ButtonGroup();
        group.add(this.jrb1);
        group.add(this.jrb2);
        jrb1.addItemListener(this);
        jrb2.addItemListener(this);
        pan.setLayout(new GridLayout(1,4));
        pan.add(this.a);
        pan.add(this.jrb1);
        pan.add(this.b);
        pan.add(this.jrb2);
        this.frame.add(pan);
        this.frame.setSize(200,100);
        this.frame.setVisible(true);
        this.frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                super.windowClosing(e);
                System.exit(1);
            }
        });
    }
    @Override
    public void itemStateChanged(ItemEvent e) {
        if(e.getSource()==jrb2){
            a.setText("未选中");
            b.setText("选中");
        }else {
            b.setText("未选中");
            a.setText("选中");
        }
    }
}
public class Hello {
    public static void main(String[] args) {
        new MyRadio();
    }
}