Error while parsing custom services jar file

after watching this tutorial
i stuck with these error

Make sure to put your service into a package. See the video at 2:53.

For anyone having a similar problem:

I had this error message, too, no details given. I was using CodeRunner 3.0.12, which was part of the ZIP I downloaded from the Backendless console (Business Logic -> Code Generation).
I then downloaded CodeRunner 3.0.19 from the website, which then provided me a Stacktrace of a ClassNotFoundException.

So in the end I had to add a dependency - problem solved.