下面是部分代码
// 打开菜单项的功能实现
        openitem.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            JFileChooser jfile = new JFileChooser();
        FileNameExtensionFilter filter = new FileNameExtensionFilter("*.txt","txt");  //出错行
        jfile.setFileFilter(filter);
        jfile.setVisible(true);
        int returnval = jfile.showOpenDialog(jfile);
        filePath =jfile.getDialogTitle()+jfile.getSelectedFile().getName();
        System.out.println(jfile.getSelectedFile());
        FileDialog dialog = new FileDialog(new JFrame(), "打开....",FileDialog.LOAD);
        dialog.setVisible(true);
        filePath = dialog.getDirectory() + dialog.getFile();
        System.out.println(filePath);

未找到这个类，若是引用的jar包，需要将jar添加到classpath中;若不是引用的jar包，需要导入此类