The above simulation was created with EJS ([url=http://fem.um.es/EjsWiki/]Offcial EJS WiKi Page[/url])
You can download EJS source from the above link and open it with EJS to view/edit the physics model.
However, you need to install EJS first.
You can download the jar file to run it locally (double click downloaded jar file.).
[b]Right[/b] click in the simulation region and selec [b]open EJS model[/b], it will load EJS source into EJS environment and you will be able to view the EJS source if you have installed EJS.
You can modify the model and generate new simulation with EJS (just click run/cmpile button)
Please check out [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=95.0]Easy java simulation (Download and related informations)[/url] and [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=656.0]SWF movie show step by step instructions to create java simulation with EJS[/url].
If you really want to look at the java source code, it is available under [b]output[/b] subdirectory under EJS installed directory.
For those who are familiar with EJS, you can click the VIEW EJS source link to view a web simplify version of EJS model.