How to force Java to reload class upon instantiation?

Background:
I have a MainTest class that has many buttons, each of which instantiate a class that I am coding/testing. I want the code/test cycle for these classes to be quick, and see the effect of my changes quickly, a few times a minute. MainTest which is stable takes about 20 seconds to load, which would not be a problem had I not needed to reload it for each change in the classes it instantiates. I want to load MainTest once, and when it instantiates another class, let's call it ChildTest, numerous times (upon button event), it should reload the latest version of ChildTest.

The question in short:
How do you tell the java 'new' command to reload the class from disk and not from jvm cache?

I tried Class.ForName but it didn't make a difference.
I have also tried using a custom classloader (copied from open source), to no avail.