public class User {
    private String userName;
    private String password;

    public static User user = new User();

    public void setName(String name){
        userName = name;
    }

    public String getName(){
        return userName;
    }

    public void setPassword(String pass){
       password = pass;
    }

    public String getPassword(){
        return password;
    }

}

public class Menu {

public static void register(){


    Scanner sc = new Scanner(System.in);

    do {
        System.out.println("Create your nickname:");
        User.user.setName(sc.nextLine());
    }while(User.user.getName().equals(""));

    do {
        System.out.println("Create your password:");
        User.user.setPassword(sc.nextLine());
    }while(User.user.getPassword().equals(""));
}