I am looking for a software tool that will introduce me to the basics of modeling and simulation. I have a good working knowldge of C++ and Java.
Could someone tell me the differences between NetLogo and Greenfoot? Which of these would you recommend?
I don't know about NetLogo, but Greenfoot is designed to be an environment that's easy to use for beginners to create graphical games or simulations. It may well be good for you in the sense that it handles a lot under the hood - double buffering, key input, etc. and allows you to export scenarios to the web for others to see too.
After a while you might wish to move to something more advanced, but it should definitely be a good starting point.