這是教材上關(guān)于在窗口中添加菜單，子菜單，及菜單項的一個示例，然而我敲完之后窗口并不顯示，懵逼。。。下面是源代碼：//Example.javapublic class Example?{ public static void main(String args[]) { WindowMenu win = new WindowMenu("帶菜單的窗口",20,30,190,200); }}//WindowMenu.javaimport java.awt.event.InputEvent;import java.awt.event.KeyEvent;import javax.swing.ImageIcon;import javax.swing.JFrame;import javax.swing.JMenu;import javax.swing.JMenuBar;import javax.swing.JMenuItem;import javax.swing.KeyStroke;public class WindowMenu extends JFrame{ JMenuBar menuBar; JMenu menu,subMenu; JMenuItem item1,item2; public WindowMenu(){} public WindowMenu(String s,int x,int y,int w, int h) { setBounds(x,y,w,h); setVisible(ture); setDefaultCloseOperation(DISPOSE_ON_CLOSE); } void init(String s) { setTitle(s); menuBar=new JMenuBar(); menu =new JMenu(); subMenu =new JMenu("子菜單"); item1=new JMenuItem("菜單項1",new ImageIcon("a.gif")); item2=new JMenuItem("菜單項2",new ImageIcon("b.gif")); item1.setAccelerator(KeyStroke.getKeyStroke('A')); item2.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,InputEvent.CTRL_MASK)); menu.add(item1); menu.addSeparator(); menu.add(item2); menu.add(subMenu); subMenu.add(new JMenuItem("子菜單里的菜單項",new ImageIcon("c.gif"))); menuBar.add(menu); setJMenuBar(menuBar); }}請求大神指教！?。?！謝謝啦。