Reobfuscate and extract modified classes

[DelofJ]

Hi, I modded Minecraft a bit, but now I want to reobfuscate and extract the modified classes so I can reinject these classes into the official jar like in the old days of modding (opening the jar with a zip archiver, deleting the META-INF, replace the classes with the mod) to run the game with the mod, how can I do that ?