I've been paid to write Java for multiple companies, and I'd like everyone to know that I don't know Java.

I don't see how that refutes anything. Java is a complicated language and I personally wouldn't hire anyone who are vain enough to say "I know Java". In any case, the very next sentence of the article is "Not very well, anyway", which definitely supports the claim that he taught himself Java.

You wouldn't hire anyone who says "I know Java"? That seems extreme. Some people do know Java and are completely justified in saying so.

Well, I suppose it was a bit of hyperbole on my part, but the thought of someone saying "I know Java" made me think of something like that "I know Kung Fu" moment from The Matrix, as if there's some amount of knowledge after which you just have the skill. I consider Java to be one of these things like Kung Fu, or Chess, or photography, where thinking that you now know it just means that you're so early in your learning process that you can't see the full lay of the land yet.

Yes, but then the rest of the sentences after that go to great length to explain his actual programming background, in QuickBASIC, and how he applied his knowledge of fundamentals to the scenario at hand.