如何在Java中保存应用程序内编辑的txt文件

我一直在坚持如何在正在创建的文本编辑器中保存文件的方法，如果您能帮助我，请看这里的代码

import java.awt.*;

import java.awt.event.*;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileReader;

import java.io.IOException;


import javax.swing.*;

import javax.swing.border.*;


public class test1 {

    public static void main ( String[] args )
    {
        JButton b1 = new JButton("Press to read a file");
        JPanel middlePanel = new JPanel ();
        middlePanel.setBorder ( new TitledBorder ( new EtchedBorder (), "Text Reading Box" ) );

        // create the middle panel components

        final JTextArea display = new JTextArea ( 16, 58 );
        display.setEditable ( false);
        JScrollPane scroll = new JScrollPane ( display );
        scroll.setVerticalScrollBarPolicy ( ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS );

        //Add Text area in to middle panel
        middlePanel.add ( scroll );

        // My code
        JFrame frame = new JFrame ("Text Reader 0.4 Beta"); 
        frame.add ( middlePanel );
        frame.add(b1, BorderLayout.NORTH);
        frame.pack ();
        frame.setLocationRelativeTo ( null );
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible ( true );
        frame.setLayout(new BorderLayout());
        b1.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                JFileChooser chooser = new JFileChooser();
                chooser.showOpenDialog(null);
                File f = chooser.getSelectedFile();
                String filename = f.getAbsolutePath();

                try {

                    FileReader reader = new FileReader(filename);
                    BufferedReader br = new BufferedReader(reader);
                    display.read(br, null);
                    br.close();
                    display.requestFocus();

                }

                catch(Exception error) {
                    System.err.println("Could'nt read a file");
                }
            }

          });

    }
}