I was asked to build a java system that will have the ability to load new code while running
You might want to base your system on OSGi (or at least take a lot at it), which was made for exactly this situation.
Messing with classloaders is really tricky business, mostly because of how class visibility works, and you do not want to run into hard-to-debug problems later on. For example, Class.forName(), which is widely used in many libraries does not work too well on a fragmented classloader space.
