请大家帮忙看一个关于错误的有关问题

//目前实现了可以将文本内容读入到文本区并显示的功能//问题一:在运行程序时,会有异常信息一闪而过.package Notepad_new;import javax.swing.*;import java.awt.*;import java.awt.Event.*;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.io.*;public class NotePad{    public static void main(String args[]){        try{            JFrame frame = new NoteFrame();                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        frame.setVisible(true);        }catch(Exception e){            System.out.println(e.toString());        }            }}class NoteFrame extends JFrame{    public NoteFrame(){                setSize(400,600);        Container c = getContentPane();        TextPanel p = new TextPanel();        area = p.area;        JScrollPane scroll = new JScrollPane(area);        p.add(scroll);        add(p);                        JMenuBar menubar = new JMenuBar();        this.setJMenuBar(menubar);        JMenu fileMenu = new JMenu("文件");        JMenuItem openItem = new JMenuItem("打开");        openItem.addActionListener(new ActionListener(){            public void actionPerformed(ActionEvent e){                JFileChooser chooser = new JFileChooser();                chooser.setCurrentDirectory(new File("."));                chooser.showOpenDialog(NoteFrame.this);                fileName = chooser.getSelectedFile().getPath();                try{                    File f = new File(fileName);                    BufferedInputStream in = new BufferedInputStream(new FileInputStream(f));                    int n = in.available();                    byte[] b = new byte[n];                    in.read(b,0,n);                    fileText = new String(b);                    area.setText(fileText);                }catch(IOException e1){                    System.out.println(e.toString());                }            }        });        fileMenu.add(openItem);        JMenuItem exitItem = new JMenuItem("退出");        exitItem.addActionListener(new ActionListener(){            public void actionPerformed(ActionEvent e){                System.exit(0);            }        });        fileMenu.add(exitItem);        menubar.add(fileMenu);        pack();        area.setText(fileText);    }        public static String fileText,fileName;    public static JTextArea area;}class TextPanel extends JPanel{    public TextPanel(){        setSize(400,400);        area = new JTextArea(20,20);        BorderLayout layout = new BorderLayout();        this.setLayout(layout);        add(area,layout.CENTER);    }    public  static JTextArea area;}