A friend is working on a game for his graduation project and he asked me for help fixing a rather tricky bug.
After a good hour and a half I admitted defeat and wrapped his entire game loop in a try-catch. It works flawlessly.

Next time starts with try catch then it won't defeat you again.

Actually I usually prefer to try catch and alert so that I can discover problems easily. Luckily it's well going.

what was the exception message?

@DataJockey It was a ConcurrentModificationException. User input is being handled on a different thread (Swing UI thread) than the game logic and rendering, so when the user triggered an action that spawned a new entity at the exact moment that something on the game thread was iterating over the entity list, the whole thing crashed.

@franga2000 thx for sharing. Is there something like a ConcurrentQueue in Java?