I wrote 2 games in Java: Pong and a simple arcade shooter. It taught me a lot about state of the object. Very important concepts in games. It also taught me a lot about time management. Literally I had to use all my time and attention into the arcade shooter game because a lot of the features I never solved before in college. It is very difficult to estimate time on a feature. So features are somewhat initally complicated. It was a fun personal project.
As for horror stories, I find 4 game breaking bugs. Forunately all of them are gone!
As for advice: just get started! Don't brainstorm for too long. I made the mistake of doing that for 2 months. While the ideas all make it to the game, I could have finished the game much sooner.
Java has a pretty cool built-in library that handles the graphics side of things for you. So that would be a great way to start with.