I cant extend a class from the CurveController class and override its update method because its fields are private .
Why is that ? why shouldn't be fields of such important classes be protected so the user can extend it ? all i can do is to copy
the source of the CurveController into a NewCurveController and make its fields protected so i can extend from it later .
The world isn't fair, right!? 
Well, if you want something changed make a topic in jme2-contribution with a patch that is changing the CurveController…
For patching with eclipse have a look here:
http://www.ibm.com/developerworks/java/library/j-subversion/
until then just change it locally…
ttrocha said:
until then just change it locally...
OP was talking about copy/pasting the class and using the newly created one in their packages.. ttrocha's path is the generally more accepted approach. Rather than using the jME jar's you would check out the sources into your IDE of choice and link that to your project.
That way when you need to make a change like this all the code is there to be modified and you can post it for inclusion in the engine :D
IDE Checkout Tutorials: Eclipse
NetBeans
right