Thread: Java UML diagram question

I have a java program to write and the professor gave us a UML diagram to follow. It all makes sense except for the part where there are dollar signs. What do these dollar signs mean? Here's what it looks like:

Wrestler
- firstName : String The wrestler’s first name.
- lastName : String The wrestler’s last name.
- weight : double The wrestler’s weight.
- grade : int The wrestler’s grade expressed as a number.
$sortKey int A class-level variable used to specify how all Wrestler objects should be sorted.
$COMPARE_BY_NAME : int = 1 A class-level constant used to specify that Wrestlers should be sorted by last name.

Do these dollar signs indicate constants? If so, then why does this method have a dollar sign in front of it too?
$setKey(int):void A class-level method used to set the sort key for all Wrestler objects.