I've got the following problem: I want to show in a JFrame a flickering, i.e. a noise as you see it on your TV if you recieve no sender. It ought to be quiet fast (say, every 20 ms). I tried to use getGraphics(), and it worked fine on a PC, but failed on a Macintosh (getGraphics() returned null there). How would you programm such a flickering? I'm happy for any ideas.