FSM example: robot states

robot

public class Charging : State {
 
    public override void Execute( Robot entity ) {
        if ( entity.charge == 100f ) {
            entity.fsm.ChangeState( SearchHumans.Instance );
        } else {
            entity.DoCharge();
        }
    }
 
    // singleton
    private static instance;
    public static Instance { 
        if ( instance != null ) { 
            return instance;
        } else {
            instance = new Charging();
            return instance;
        }
    }
 
}
 
public class SearchHumans : State {
 
    public override void Execute( Robot entity ) {
        if ( entity.isHumansDetected() ) {
            entity.fsm.ChangeState( KillAllHumans.Instance );
        } else {
            entity.SearchHumans();
        }
    }
 
    // singleton code   
}
 
public class KillAllHumans : State {
 
    public override void Execute( Robot entity ) {
        if ( entity.allHumansIsDead() ) {
            entity.fsm.ChangeState( Charging.Instance );
        } else {
            entity.KillHumans();
        }
    }
 
    // singleton code   
}