Java如何制作MDI窗體

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

 class JInternalFrame1 extends JFrame implements ActionListener{
   
    JDesktopPane desktopPane;
    int count = 1;
   
    public JInternalFrame1() {
        super("JInternalFrame1");
        Container contentPane = this.getContentPane();
        contentPane.setLayout(new BorderLayout());
       
        JButton b = new JButton("Create New Internal Frames");
        b.addActionListener(this);//當用戶按下按鈕時，將運行actionPerformed()中的程序
        contentPane.add(b, BorderLayout.SOUTH);
        /*建立一個新的JDesktopPane并加入于contentPane中
         */
        desktopPane = new JDesktopPane();
        contentPane.add(desktopPane);

        setSize(350, 350);
        show();
       
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                    System.exit(0);
            }
        });
    }
    /*產(chǎn)生一個可關(guān)閉、可改變大小、具有標題、可最大化與最小化的Internal Frame.
     */
    public void actionPerformed(ActionEvent e)
    {
        JInternalFrame internalFrame = new JInternalFrame(
        "Internal Frame "+(count++), true, true, true, true); 

        internalFrame.setLocation( 20,20);
        internalFrame.setSize(200,200);
        internalFrame.setVisible(true);
        //取得JInternalFrame的Content Pane,用以加入新的組件。

Container icontentPane = internalFrame.getContentPane();
        JTextArea textArea = new JTextArea();
        JButton b = new JButton("Internal Frame Button");
        /*將JTextArea與JButton對象加入JInternalFrame中。由此呆知，JInteranlFrame加入組件
         *的方式與JFrame是一模一樣。
         */
        icontentPane.add(textArea,"Center");
        icontentPane.add(b,"South");
        //將JInternalFrame加入JDesktopPane中，如此一來，即使產(chǎn)生很多JInternalFrame,JDesktopPane也
        //能將它們之間的關(guān)系管理得相當良好。
        desktopPane.add(internalFrame); 
       
        try {
            internalFrame.setSelected(true);
        } catch (java.beans.PropertyVetoException ex) {
          System.out.println("Exception while selecting");
        }
    }

    public static void main(String[] args) {
        new JInternalFrame1();
    }
}