void editProfile(String usr,String pswd,String newFname,String newLname,String newUsername, String newPassword){
        String filepath ="user.txt";
        String tempFile = "temp.txt";
        File oldFile = new File(filepath);
        File newFile = new File(tempFile);

        try
        {
            FileWriter fw = new FileWriter(tempFile,true);
            BufferedWriter bw = new BufferedWriter(fw);
            PrintWriter pw = new PrintWriter(bw);

            RandomAccessFile raf = new RandomAccessFile(filepath,"rw");
            for(int i=0;i<ln;i+=7){
                String forUser = raf.readLine().substring(9);
                String forPswd = raf.readLine().substring(9);
                String role = raf.readLine().substring(5);
                String balance = raf.readLine().substring(8);
                String firstName = raf.readLine().substring(11);
                String lastName = raf.readLine().substring(10);

                if(usr.equals(forUser)&pswd.equals(forPswd)){

                    pw.println("Username:"+ newUsername+"\r\nPassword:"+ newPassword+"\r\nRole:"+role +"\r\nBalance:"+ balance+"\r\nFirst Name:"+newFname+"\r\nLast Name:"+ newLname);
                    JOptionPane.showMessageDialog(null,"Login Successful");

                }else{
                    pw.println("Username:"+ forUser+"\r\nPassword:"+ forPswd+"\r\nRole:"+role +"\r\nBalance:"+ balance+"\r\nFirst Name:"+firstName+"\r\nLast Name:"+ lastName);
                }
            }

            pw.flush();
            pw.close();
            oldFile.delete();
            File dump  = new  File(filepath);
            newFile.renameTo(dump);
        }catch(IOException ex){
            JOptionPane.showMessageDialog(null,"fail");
        }
    }

     private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        editProfile(username.getText(),password.getText(),newFname.getText(),newLname.getText(),newUsername.getText(),newPassword.getText());
    }

我正在做一个页面，客户可以通过输入他们的旧用户名和密码，然后输入新用户名和密码来编辑他们的个人信息。我试图读取旧用户名和密码，以匹配文本文件中的数据，并更新新用户名和密码。
运行程序时没有响应，但我无法识别代码中的错误。有什么建议来修复这个错误吗？