class Account extends BaseActor {
    public static final Logout logout = new Logout();
  
    static final LoginSuccess success = new LoginSuccess();
  
    final String login;
  
    String password;
  
    {
        behavior(State.FREE)
            .Case(
                auth -> {
                    if(password.equals(auth.password)) {
                        reply(success);
                        become(State.AUTH);
                    } else
                        reply(LoginFail.WRONG_PASSWORD);
                },
                Auth.class
            );
          
        behavior(State.AUTH)
            .Case(
                auth -> reply(LoginFail.IN_USE),
                Auth.class
            )
            .Case(
                logout -> become(State.FREE),
                Logout.class
            );
        ...
    }
  
    enum State {
        FREE,
        AUTH,
        BLOCK,
        ...
    }
  
  
    public static class Auth {
        final String password;
      
    }
  
    public static class LoginSuccess {
  
    }
  
    public static class Logout {
  
    }
  
    public static enum LoginFail {
        IN_USE,
        WRONG_PASSWORD,
        ....
    }
}