what "concern metrics" means in Software Engineering

Recently, I was reading a paper whose name is "On the Effectiveness of Concern Metrics to Detect Code Smells: An Empirical Study".

I come from a non-English speaking country, and I can not quite understand what Concern Metrics means in the field of software engineering.

It is not referring to the relationship between objects?

I have some understanding of java and c #, some people may be able to use java to give me an example.

Thanks.