For all the applets on this forum which was created with "Easy Java Simulations(EJS)". You will be able to see the EJS source. Just click "load ejs as signed applet". You can find out all the variables and equations used in the simulation.

However, for all the applets in this categories (JDK1.0.2 simulations). They were created almost 10 years ago with JDK1.0.2. I do not have time to find all the source code and put it in the downloaded zip files.
If you really interesting the programming. Try to study the java code generated by ejs.
(If you download it, there are several hundreds simulations/with EJS sources in the distribution).  :o