按下jButton时如何将数据追加到文件中

Question

我一直在创建一个GUI应用程序，为学生注册数据，数据填充在提供的JTextfields中。按下提交按钮后，我对其进行了编程，使其以我喜欢的某种方式（排列）将数据存储到文件中。对于第一次提交，该程序运行良好并将数据存储到文件中，但是在其他连续enter code here提交（即当学生重新填充时）时，该程序将覆盖或完全不写入文件。下面是到目前为止的代码：

import javax.swing.*;

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.io.PrintStream;

public class StudentAssignment extends JFrame {

    private JLabel lblFname, lblbSname, lblRegNo, lblPos;

    private JButton btnsubmit;

    private JTextField txtFname, txtSname, txtRegNo, txtPos;

    private JPanel panel1, panel12, panel3, panel4,panel5;

    private int i = 1;

    private File myFile;

    private FileWriter fw;

    private PrintStream ps;

    public StudentAssignment() throws Exception{

        componentInitialization();

        setVisible(true);

        myFile =new File("Mustard.txt");

        fw = new FileWriter(myFile,true);

        ps = new PrintStream(myFile);

        actionListeners();

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }

    public void componentInitialization(){

        setBounds(200, 200, 300, 300);

        setTitle("Mustard's Frame");

        setLayout(new GridLayout(5,1));

        lblFname = new JLabel("First Name");

        txtFname = new JTextField(10);

        panel1 = new JPanel();

        panel1.add(lblFname); panel1.add(txtFname);

        lblbSname = new JLabel("Surname");

        txtSname = new JTextField(10);

        panel12 = new JPanel();

        panel12.add(lblbSname); panel12.add(txtSname);

        lblRegNo = new JLabel("Registration Number");

        txtRegNo = new JTextField(10);

        panel3 = new JPanel();

        panel3.add(lblRegNo); panel3.add(txtRegNo);