They might look tacky in first place, but I assume they are related to the dollar signs in the stacktraces of code with threading and anonymous functions. :)

    ...
    at com.company.IdentityVerifier$$anonfun$go$2$$anonfun$apply$2.apply$mcII$sp(IdentityVerifier.scala:19)
    ...
    at com.company.UserCreatorMain$1.run(UserCreatorMain.java:37)
    ...