This is if batch doesn't work.

Make a file called *.zip

Add a folder called META-INF.
Add a file in that folder called MANIFEST.MF(open it with notepad)
MAKE SURE IT ENDS ON A BLANK LINE!!!

Main-Class: the class that will be executed first.
Created-By: YOUR JDK VERSION

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Put all those files in *.zip

Rename to *.jar
Execute.

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In case you didn't figure it out already, *.zip means whatever you want to call it.

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Jar is the same compression as Zip.