[quote]
i think i know what is your problem.

file name too long.

D:\EasyJavaSimulation\EJS_4.3.0_100613\EJS_4.3.0\workspace\source\users\sgeducation\lookang\users_sgeducation_lookang_ejs_EarthAndMoon3D_EarthAndMoon3D.xml

rename the file to EarthAndMoon3D.xml before you save it to your PC. Do not change file name in Ejs editor mode, the file is already not read correctly so it will not work still.

i think java has some number of character restriction from the root directory so how i solve this problem is rename file to a short name.
try it
[/quote]
I really do it from first time i change however i will wait answer see with prof Hwang what is the problem in my system