Java编程：初学者的登录界面代码求助

import java.awt.*;
import java.awt.event.*; 
import java.awt.datatransfer.*;
import java.io.*;  import javax.swing.*;
import javax.swing.text.*;
 class JNotePadUI extends JPanel 
{ 
    // 变量定义 
    JTextArea jta = new JTextArea("", 24, 40); 
    JScrollPane jsp = new JScrollPane(jta);
    // 菜单条 
    JMenuBar jmb = new JMenuBar(); 
    JMenu file = new JMenu("文件(F)", true); 
    JMenu edit = new JMenu("编辑(E)", true); 
    JMenu help = new JMenu("帮助(H)", true);
    // 工具条 
    JToolBar toolBar = new JToolBar();
    // 菜单内容 
    JMenuItem jmi; 
    // 实例化剪切板  
    Clipboard clipbd = getToolkit().getSystemClipboard(); 
    String text = "";   
    // 构造函数  
    public JNotePadUI()  
    {  
        class newL implements ActionListener  
        {    
            public void actionPerformed(ActionEvent e)   
            {    
                jta.setDocument(new PlainDocument()); 

            }  
        }
        // 打开功能  
        class openL implements ActionListener  
        {   
            public void actionPerformed(ActionEvent e)   
            {   
                JFileChooser fc = new JFileChooser(); 
                int returnVal = fc.showDialog(JNotePadUI.this, "打开");   
                if (returnVal == JFileChooser.APPROVE_OPTION)    
                {     
                    String file = fc.getSelectedFile().getPath();
                    if (file == null)  
                    {      
                        return;   
                    }    
                    // 读取文件    
                    try     
                    {      
                        Reader in = new FileReader(file);    
                        char[] buff = new char[4096];      
                        int nch;      
                        while ((nch = in.read(buff, 0, buff.length)) != -1)       
                        {     
                            jta.setDocument(new PlainDocument());      
                            jta.append(new String(buff, 0, nch));   
                        }   
                    }      
                    catch (IOException io)    
                    {