I'm creating a tower defense game and I'm having logistical issues trying to figure out how to best have all of the enitites do their apporiate task.

I have considered just constantly looping through a list of all the game entities calling a onAction() method, but I'm not sure if that is effective.

I have also considered having each entity be a thread, but when I am dealing with hundreds of entities, some of which don't need thread time, I'm back to square one.

Can I get any suggestions on a solid approach? Am I on the correct track with my first idea?

Thanks for any help ~Aedon