An applet for playing around with
WikiPedia:Mandelbrot_set of varying exponents. An exponent of 2 is the most common one, but higher ones -although slower to calculate- also generate interesting images.
The UI controls are functional while an image is drawn; you don't have to wait until it's done. Clicking on the "Approximation: On/Off" label toggles approximation mode, which shows an increasingly finegrained approximation of the final image. This is useful to get a first idea of what an image looks like, and zoom/pan without having to wait for the whole image to be finished.
Since applets are out of fashion nowadays, it can also be run from the command line via "appletviewer SimpleMandel.java".
The source code can be found here. This is some of the earliest Java code I ever wrote, so the code quality is not really what I would like it to be nowadays :-)
CodeSnippets