First check if you have Java Web Start.
You can do this with the command
% locate javaws
If you do not have Java Web Start you need to download it. On 64-bit systems, you need to install the 32-bit version of java. When you click the Launch below, if it asks what to run it with, you need to find the javaws on you system.
(If you want to compile java, you need the full java development kit.)
If you have Java Web Start you can start the calculator just by clicking this link:
Warning: when you launch for the first time you will getting a message warning you that I don't have a valid certificate (they cost a $100 or so) and asking if you still want to start the program. Ignore this warning. The first time you Launch will be slow since many files may have to be downloaded but after that it will be fast.
After the first time: You can start the program either from this web page or just by executing javaws.