代码如下：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class Java_2 {
    public static void main(String[] args) {
        RadioButtonFrame frame = new RadioButtonFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //*********Found********** 
        ___________________;
    }
}
 
class RadioButtonFrame extends JFrame {
    public RadioButtonFrame() {
        setTitle("Radio按钮实例");
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        Container contentPane = getContentPane();
        label = new JLabel("热烈庆祝Java程序语言开考三周年");
        label.setForeground(Color.yellow);
        contentPane.setBackground(Color.red);
        label.setFont(new Font("黑体", Font.PLAIN, DEFAULT_SIZE));
        contentPane.add(label, BorderLayout.CENTER);
        buttonPanel = new JPanel();
        group = new ButtonGroup();
        addRadioButton("小", 8);
        addRadioButton("中", 12);
        addRadioButton("大", 18);
        addRadioButton("特大", 30);
        contentPane.add(buttonPanel, BorderLayout.SOUTH);
    }
 
    public void addRadioButton(String name, final int size) {
        boolean selected = size == DEFAULT_SIZE;
        //*********Found********** 
        JRadioButton button = new ____________________(name, selected);
        group.add(button);
        buttonPanel.add(button);
        ActionListener listener = new ActionListener() {
            //*********Found********** 
            public void actionPerformed(_____________________ evt) {
                label.setFont(new Font("黑体", Font.PLAIN, size));
            }
        };
        //*********Found********** 
        button.addActionListener(__________________);
    }
    public static final int DEFAULT_WIDTH = 340;
    public static final int DEFAULT_HEIGHT = 200;
    private JPanel buttonPanel;
    private ButtonGroup group;
    private JLabel label;
    private static final int DEFAULT_SIZE = 12;
}