this is some code taken from the net, modified a bit, that I'm trying to understand. The idea is to bounce a ball. Currently the ball bounces in a continuous line, but I can't see where I'm messing up.
Some very old-fashioned looking code there, with _x and _y. That is an acceptable format in C, but not considered correct style in Java. And some odd features like an empty catch and a SUID of 1L. Also using thread priorities (which is probably unnecessary) may lose portability.
Try super.paint(g); as the first line of the paint() method.