覆盖Java中的文本文件

Question

The application should be able to register a new user and save data to text file which is already has many users' data. This code is works but it doesn't save new data to text file. How should I overwrite the text file? Should I read data from text first and write all the data back to text file or there is a way to just add a new line and write new data there?

registerB.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e){
                            String getFullname = fullnameT.getText();
                            String getUsername = usernameT.getText();
                            String getPassword = passwordT.getText();
                            String getPN = pnT.getText();
                            String getEmail = emailT.getText();
                            boolean theSame = false;
                            String []Fullname = new String[20];
                            String []Username = new String[20];
                            String []Password = new String[20];
                            String []PN = new String[20];
                            String []Email = new String[20];

            if(!getFullname.isEmpty() && !getUsername.isEmpty() && !getPassword.isEmpty() && !getPN.isEmpty() && !getEmail.isEmpty()){
                int k = 0;
                try {
                    Scanner in = new Scanner (new FileReader("login.txt", true));
                    while (in.hasNext()) {
                        Fullname[k] = in.next();
                        Username[k] = in.next();
                        Password[k] = in.next();
                        PN[k] = in.next();
                        Email[k] = in.next();
                        in.next();

                        if(getUsername.equals(Username[k])){
                            JOptionPane.showMessageDialog(null, "Username already has been registered.");
                            theSame = true;
                            break;
                        }
                        k++;
                    }
                }catch(Exception ew){}
                try
                {
                    String path = "login.txt";

                    File file = new File(path);

                    FileWriter fileWriter = new FileWriter(file,true);

                    BufferedWriter bufferFileWriter  = new BufferedWriter(fileWriter);

                    fileWriter.append("," + getFullname + "," + getUsername + "," + getPassword + "," + getPN + "," + getEmail +"," + "\n");

                    bufferFileWriter.close();

                    System.out.println("User Registration Completed");

                }catch(Exception ex){
                    System.out.println(ex);
                }
            else{
                JOptionPane.showMessageDialog(null, "One or some of the fields is/are empty");
            }
        }
    });

The text file format is like this

fullname,username,password,phonenumber,email fullname,username,password,phonenumber,email

Answer 1

This is wrong new FileReader("login.txt", true)

FileReader does have this constructor

Change new FileWriter("login.text") to new FileWriter("login.text", true)

the true will append the new data to the existing data