java之swing实现复选框的方法

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class test extends JApplet
implements ItemListener{
  JTextField jtf;
  public void init(){
    Container contentPane = getContentPane();
    contentPane.setLayout(new FlowLayout());
    ImageIcon a1 = new ImageIcon("D:/data/Images/6.gif");
    ImageIcon a2 = new ImageIcon("D:/data/Images/7.gif");
    ImageIcon a3 = new ImageIcon("D:/data/Images/8.gif");
    JCheckBox cb = new JCheckBox("C", a1);
    cb.setRolloverIcon(a2);
    cb.setSelectedIcon(a3);
    cb.addItemListener(this);
    contentPane.add(cb);
    cb = new JCheckBox("C++", a1);
    cb.setRolloverIcon(a2);
    cb.setSelectedIcon(a3);
    cb.addItemListener(this);
    contentPane.add(cb);
    cb = new JCheckBox("java", a1);
    cb.setRolloverIcon(a2);
    cb.setSelectedIcon(a3);
    cb.addItemListener(this);
    contentPane.add(cb);
    jtf = new JTextField(15);
    contentPane.add(jtf);
  }
  public void itemStateChanged(ItemEvent ie){
    JCheckBox cb = (JCheckBox)ie.getItem();
    jtf.setText(cb.getText());
  }
}