Sharing state is what actor model tries to eliminate, it has a very strong locality concept. Singleton in OOP (which you have to implement atomic and thread saf

Sharing state is what actor model tries to eliminate, it has a very strong locality concept. Singleton in OOP (which you have to implement atomic and thread safety often by yourself) can be easily implemented as an actor. Erlang has gen_server for this exact scenario. About isolation, you can actually impose class isolation in OO languages by declaring all variables as private. Public variable can never happen in actor model