JAVA Login Page; How to use Read Notepad Twice?

Question

I am asking for my JAVA program, I am dealing with the Login Page. In my codes. I have a priming of the Read Methods to get an Array List. Then in Registration Button, once I already inputted a data, btw I used bufferedWriter, so it will append on my existing .txt file.

Then here is my problem , the Array List is already not updated since the data arrayed is only in the priming, means only from the start of the program, what if I already have my new inputs, it will become invalid credentials in my login method.. I tried copy-pasting my priming in the registration button method and private class method but still not working , please help thank you so much.

Here is my codes for my scanner method:

private void initialize() throws FileNotFoundException {

    String datas = "";
    Scanner notePad = new Scanner(new File("loginData.txt"));
    List<String> temps = new ArrayList<String>();

    while (notePad.hasNext()) 
    {
      datas = notePad.next();
      temps.add(datas);
    }
    notePad.close();
    String[] dataFile = temps.toArray(new String[0]);
    int mainCount = dataFile.length-1;

and the frame codes follows including my buttons. Skipping to the registration button method, here is the code.

JButton registerButton = new JButton("REGISTER");
    registerButton.setFont(new Font("Arial", Font.BOLD, 12));
    registerButton.addActionListener(new ActionListener() {
        @SuppressWarnings("deprecation")
        public void actionPerformed(ActionEvent e) 
        {
            int countRegister = 0;

            while (!registerEmail.getText().equalsIgnoreCase(dataFile[countRegister]) && mainCount >= countRegister)
                {
                countRegister = countRegister + 2;
                    if (mainCount < countRegister) 
                    {
                    break;
                    }
                }

            if (mainCount <= countRegister) // No Existing Account
            {   
            try {
                FileWriter writer = new FileWriter("loginData.txt", true);
                BufferedWriter bufferedWriter = new BufferedWriter(writer);
                bufferedWriter.newLine();
                bufferedWriter.write(registerEmail.getText());
                bufferedWriter.newLine();
                bufferedWriter.write(registerPassword.getText());
                bufferedWriter.close();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            JOptionPane.showMessageDialog(frame, "Registered successfully, you can now login.", "Success", JOptionPane.INFORMATION_MESSAGE);
            }
            else
            {
            JOptionPane.showMessageDialog(frame, "Sorry, you have entered an existing account.", "Error", JOptionPane.ERROR_MESSAGE);   // Existing Account
            }
        }
    });
    registerButton.setBounds(194, 502, 97, 23);
    frmImma.getContentPane().add(registerButton);

Answer 1

You can make a method to get the data and compare, before your logic call this method to get the refresh input

private String[] data = new String[0];

private void selectData() throws FileNotFoundException {
    Scanner scanner = new Scanner(new File("loginData.txt"));
    List<String> temps = new ArrayList<String>();
    while (notePad.hasNextLine()) {
      temps.add(notePad.nextLine());
    }
    scanner.close();
    dataFile = new String[temps.size()];
    dataFile = arrlist.toArray(dataFile);
}

, You can use NIO from JDK8+

private void selectData() throws IOException{
   dataFile = Files.lines(Paths.get(new 
   File("C:\\data.txt").getPath())).toArray(String[]::new);
}