1. launch EJS and open the file Collision2D.xml for the download link on first post
2. click on edit options button
3. a pop up on EJS options appears, first tab uncheck tickbox remove java files after compiling
4. the default is to remove for this file
5. use your computer explorer to goto F:\EasyJavaSimulation\EJS_4.1_081216\EJS_4.1\workspace\output\Collision2D_e.java    location may defer depend on what you expanded EJS.
6. i assume u are using EJS 4.1, for EJS 3.47, the idea is similar :)


try it!

[b][color=blue]i may be able to make a screenvideo by this weekend! watch this space for it!
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Help U:
i have attached for you incase your unusually problem
"I can't compile and run it coz the main class which is Collision2D_e, extends this right ..org.opensourcephysics.ejs.AbstractModel and so with the other java programs so i don what to do it just can't run without this org package"

is bugging you.

Suggestion:
Try downloading a fresh copy from www.um.es/fem/Ejs/
may solve your problem about
"I can't compile and run it coz the main class which is Collision2D_e, extends this right ..org.opensourcephysics.ejs.AbstractModel and so with the other java programs so i don what to do it just can't run without this org package"

remember to attribute your derived work like one of these
This work is licensed under a Creative Commons Attribution 2.5 Taiwan License.  ;)