The text is unclear what this method does, but said that sometimes what you should see on the screen is not there, and using this method can help with that. I shrugged it off, but earlier, one of my message boxes came up blank. I closed it, and the program continued as if nothing had happened, so I'm guessing I could have used System.flush() somehwere? How do I know when and where to use it?
It's System.out.flush(). Basically, you need to use it if you call System.out.print() (not println()) and want the output to appear on the screen right away, as opposed to later after the next println() call. It won't affect GUI message boxes at all -- it's only related to console output.