Is this observer pattern implementation proper?

Question

Hi

Refer code below which I did for observer pattern demo:
https://www.sololearn.com/compiler-playground/cDOXVq3r9ItO

Feel free to share your views on same. Any improvement advice is most welcome.

Also I have two doubts as below :
My notification is not generic. Right? Notify expects string message as an argument. Isn't it a tightly coupled code? How to avoid this and come up with better design? I feel that current observer is restricted to notify string message and curious to know generic solution.
https://code.sololearn.com/cDOXVq3r9ItO/?ref=app

Answer 1

correct command gives correct result