How to create a simple state machine in java

Question

I am currently learning java and would like to know how to control state in a OO way. I implemented a Pong app. If I wanted multiple states like gameplay and menu, and each one

Answer 1

You can simulate a basic FSM (Finite State Machine) using enums:

public enum State {

    ONE {
        @Override
        public Set possibleFollowUps() {
            return EnumSet.of(TWO, THREE);
        }
    },

    TWO {
        @Override
        public Set possibleFollowUps() {
            return EnumSet.of(THREE);
        }
    },

    THREE // final state 

    ;
    public Set possibleFollowUps() {
        return EnumSet.noneOf(State.class);
    }

}

While the code to generate this will be very verbose if things get more complicated, the nice part is that you get compile-time safety, thread-safety and high performance.