本题程序的功能是通过菜单打开一个图像文件。窗臼中有一个菜单“File”，其中包括菜单项“Open”和“Exit”。单击菜单项“Open”可弹出一个打开对话框，选中一个图像文件后单击“打开”按钮返回主窗口，则选中的图像文件显示在窗口中。单击菜单项“Exit”可退出程序。请将下述程序补充完整(注意：不得改动程序的结构，不得增行或删行)。
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
public class advance
public static void main(String[] args)
JFrame frame = new ImageViewerFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.show ();
class ImageViewerFrame extends JFrame
public ImageViewerFrame()
setTitle("advance");
setSize(DEFAULT WIDTH,DEFAULT_HEIGHT);
label = new JLabel();
Container contentPane = getContentPane();
contentPane.add(label);
______;
chooser.setCurrentDireetory(new File("."));
JMenuBar menuBar = new JMenuBar();
______;
JMenu menu = new JMenu("File");
menuBar,add (menu);
JMenuItem openItem = new JMenuItem("Open");
menu.add(openItem);
openItem.addActionListener(new ActionListener()
______
int r = chooser.showOpenDialog(null);
if(r == JFileChooser.APPROVE_OPTION)
String name = chooser.getSelectedFile().getPath();
label.setIeon(new ImageIcon(name));
);
JMenuItem exitItem = new JMenuItem("Exit");
menu.add(exitItem);
exitItem.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent event)
System.exit(0);
);
private JLabel label;
private JFileChooser chooser;
private static final int DEFAULT_WIDTH=300;
private static final int DEFAULT_HEIGHT=400;
