Can't host an Agrarian Skies Server?

[gpg5]

So every time I try to host Agrarian Skies, I get an error *check bottom of post*. I've downloaded the server 3 times and it's still having problems.

Link: http://pastebin.com/nUZDdpSc

 

[GhoulHater]

Concurrent modification exception usually means outdated java, but in this case it could be that it won't run on java 8? Try using java 7 and see if that works any better.