I'm going to edit the Opera Mini v6.5 server because it is blocked in our country.
Now I have unpacked the .apk file extracted classes.Dex then converted it via dex2jar.bat, now modified the server.
My problem is I want to repack the .jar or .class to classes.Dex. How do I do it?

Here is a solution that was helpful in my case...
Suppose .jar file sits in "c:\temp\in.jar". In command prompt window cd to ..\android-sdk\platform-tools. To get .apk execute:
To get .dex file execute: