How to save jtable data?

I am a newbie in Java. I have a problem with making the program save the data in the txt file from the table and show it again after restart. I don't have idea how to make it. Can somebody help me with making this programme with auto-saving and keeping table info in txt file and then viewable table after restart? I would be very grateful ;)

Ui.java:

import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;

public class Ui extends Main {
    public DefaultTableModel m = new DefaultTableModel();
    public JTable jt = new JTable(m);
    static JMenuBar menuBar = new JMenuBar();

    public void table(){
        m.addRow(new String[] {"a1"});
        m.addRow(new String[] {"a2"});
        m.addRow(new String[] {"a3"});
        m.addColumn("1");
        m.addColumn("2");
        m.addColumn("3");
        m.addColumn("4");
        m.addColumn("5");

        JScrollPane sp = new JScrollPane(jt);
        sp.setBounds(0,0,628,444);

        frame.getContentPane().add(sp);
}
    public void bar()  {
        frame.setJMenuBar(menuBar);

        JMenu menu2 = new JMenu("File");
        JMenuItem m2_1 = new JMenuItem("Exit");
        JMenuItem m2_2 = new JMenuItem("Save");
        m2_1.addActionListener((event) -> System.exit(0));
        m2_1.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_W, ActionEvent.CTRL_MASK));
        menu2.add(m2_2);
        menu2.add(m2_1);
        menuBar.add(menu2);

        JMenu menu1 = new JMenu("Help");
        JMenuItem m1_1 = new JMenuItem("Contact ");
        JMenuItem m1_2 = new JMenuItem("About ");
        menu1.add(m1_1);
        menu1.add(m1_2);
        menuBar.add(menu1);

        JMenu menu3 = new JMenu("Add");
        JMenuItem m3_1 = new JMenuItem("Add row");
        menu3.add(m3_1);
        menuBar.add(menu3);

        m1_1.addActionListener(e -> JOptionPane.showMessageDialog(null,
                "Text",
                "Contact", JOptionPane.PLAIN_MESSAGE));
        m1_2.addActionListener(e -> JOptionPane.showMessageDialog(null,
                "Text ",
                "About", JOptionPane.PLAIN_MESSAGE));
        m3_1.addActionListener(e -> m.addRow(new String[]{}));
    }
}

Main.java:

import javax.swing.*;
import java.awt.*;

public class Main  {
    static JFrame frame = new JFrame("Title of frame");
    public static void main(String[] args)  {
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch (UnsupportedLookAndFeelException | ClassNotFoundException | InstantiationException |
                 IllegalAccessException e) {
            throw new RuntimeException(e);}
        
        Ui p = new Ui();
        p.table(); p.bar();
        
        Image icon = Toolkit.getDefaultToolkit().getImage("icons\\logo.jpeg");
        frame.setIconImage(icon);
        
        frame.setLayout(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(645, 506);
        frame.setResizable(false);
        frame.setVisible(true);
    }
}