HashMap Main

package com.company;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Menu m = new Menu();
        Scanner in = new Scanner(System.in);
        int option = 0;
        User user = null;
        while (option != 4) {
            if (user == null) {
                System.out.println("Please enter your option:");
                printMenu();
            } else {
                printMenuLoggedIn(user);
            }
            option = in.nextInt();
            switch (option) {
                case 1:
                    m.signUp();
                    user = null;
                    break;
                case 2:
                    user = m.login();
                    break;
                case 3:
                    if (user == null) {
                        System.out.println("Bye!");
                        option = 4;
                    } else {
                        m.changePassword(user);
                    }
                    break;
                case 4:
                    System.out.println("Bye!");
                    break;
                default:
                    System.out.println("Invalid option");
                    break;
            }
        }
    }

    //Printing this menu when NO user is logged in.
    public static void printMenu(){
        System.out.println("1. Sign up.");
        System.out.println("2. Log in.");
        System.out.println("3. Exit.");
    }
    //Printing this menu when user IS logged in.
    public static void printMenuLoggedIn(User user){
        System.out.println("Welcome " + user.getUsername() + "!");
        System.out.println("Please enter your option:");
        System.out.println("1. Sign up.");
        System.out.println("2. Log in.");
        System.out.println("3. Change password.");
        System.out.println("4. Exit.");
    }
}