Undo Terminal Commands! Help!

I was trying to download something for a game the other day, and I entered some code that I was told to into Terminal. Now the game freezes every time I start it. I was wondering if I could somehow undo those commands even after Terminal has been closed. Here is the code that I entered line by line:

cd ~
mkdir mctmp
cd mctmp
jar xf ~/Library/Application\ Support/minecraft/bin/minecraft.jar

rm META-INF/MOJANG_C.*
jar uf ~/Library/Application\ Support/minecraft/bin/minecraft.jar ./
cd ..
rm -rf mctmp