Help with error in plugin.

[john.]

I have an error in my plugin and I cannot find out why it's throwing an error.

Error in console: http://prntscr.com/kf2b8h

Lines that the error is: http://prntscr.com/kf2bg5 , http://prntscr.com/kf2bm2

help a nig out

Notifyz

 

[john.]

StaffOnlineGUI.class -> whats on line 27

http://prntscr.com/kf2cqf

 

[john.]

Make this;

for (Player StaffOnline :
core.
StaffOnline) {

so each has line and let's see what's wrong.

http://prntscr.com/kf2e3e

 

[Overshower]

core.staffOnline is null, where do you define/add values to it?