//declare a Map key is username and value is password
 private HashMap<String, String> users = new HashMap<>();

private void register(){
  username = get username;
    password = get password;
    if (username.equals("") || password.equals("")) {
                Print (" No username / password entered ")
            } else {
        users.put(username,password);
    }
}

 private void login() {
    username = get username;
    password = get password;
    if (username.equals("") || password.equals("")) {
                Print (" No username / password entered ")
            } else {

                //retrive the value from Map using get(key)
                if (users.get(username) != null &&
                users.get(username).equals(password)) {
                  print ("Login successfull"):

                 } else {
                    Print("Username or password does not match.
                           Please try again.");
               }
          }




--
with regards,

Karthik raja T}