Hey, I was just wandering if there was a way of obfuscating classes, because In this game i’m making I don’t want modders finding out how to, well mod the classes.
Thanks 
You shouldn’t want to do that. It’s evil.
If you still want to, this looks helpful.
Some other items on JGO answering your question, or at least, looking for answers:
http://www.java-gaming.org/topics/obfuscating-code-and-references-to-java-standard-apis/29868/view.html
http://www.java-gaming.org/topics/proguard-gui-don-t-obfuscate-1-class/25632/view.html
By the way, what makes you want modders to not be able to mod? Likely your game won’t get popular enough to be modded, anyway, so why bother? That was not meant as an insult; I’m sure the majority of people’s games here will never get modded.
Obfuscating isn’t a bad thing at all, its just a way to keep your source closed.
No, it just makes it harder to read. I good reverse engineering guy does not stop because of the classes and types named with just a letter 
Just look at Minecraft. it is obfuscated yet there are mods.
That is pointless.
Scenario 1: (Most likely) No-one will care about your game and so will not even think to mod it.
Scenario 2: (unlikely) The game will get really popular and so people will get around obfuscation anyway.
Either way, you waste you time.
Ouch bro.
----> Mission complete.
The sad truth of starting out as a game developer.
(side note: “No-one” was meant more as “almost no-one”)
And in most cases, no-one will care enough to mod your game.
Its not really about caring to mod it. Its about wanting to mod it
I concur.
It can make a big difference trying to decompile code obfuscated vs unobfuscated. It is still possible, just harder. It also makes the JARs smaller. There is nothing wrong with obfuscation.
Yepp that’s the good thing (Although the most size from your game will be the assets not the code). Tools like ProGuard also optimize stuff afair.
True, though it depends on the game (eg, 4k games). An obfuscater can rip out all the stuff you don’t use, which might be a decent chunk if only using small portions of relatively large libraries. FWIW, Spine is ~43k LOC on it’s own, not including dependencies. The JAR including that and all the dependencies (libgdx, LWJGL) is 2.2MB, without natives. Kind of scary how much effort goes into something so small. 
Unobfuscated it’s 3.9MB, so a 44% reduction. The JGLFW version of Spine is < 1.5MB obfuscated, which goes to show LWJGL could be a bit smaller.