After I make an incompatible change to one class, do I need to do a Clean and Build to see what it broke?
Turn on Track Java Dependencies in the Compiling tab of your project's Properties dialog to ensure that any class depending on a class you modified gets recompiled. Or just use FaqCompileOnSave.
Even without this, you should still see error badges on any classes broken by an edit as soon as you save it.
Applies to: NetBeans 6.0 and later