We may have found a java compiler bug in high school cs class. The program was all of 2 lines doing some very basic arithmetic and comparison. Half the class and teacher were huddled around the computer trying to figure out what the hell was going on. I was new to programming so it's hard to say with confidence. But there was nothing 'tricky' in the code, just wrong output. This was over 10 years ago but java wasn't exactly new.