private void getLoginDetails(String userType){

while(!userReader.userExists(new User(userType,
                                      userInputReader.readUsername(),
                                      userInputReader.readPassword() )){

    System.out.println("Error: Invalid username or password.");
    username = userInputReader.readUsername();
    password = userInputReader.readPassword();
    enteredUser = new User(userType, username, password);

}

}