Finished off DifferenceEngine.java today, along with HTMLCacheUpdate.java. Now working on JobQueue.java. The database code still needs a lot of refactoring, and some of the stuff in JobQueue is showing this off. The switch statements for choosing subclasses in JobQueue make me twitch.

I've had a roaring headache most of the evening, which has hampered productivity. Still, I am pleased with the progress I'm making.