The primary usecase of any directory scanner is for filesystem-based, and other usecases are secondary. I had considered adding an interface, but java lacks Duck-Typing,  and since the primary users will be using java.io.File, requiring some interface would require anyone trying to use java.io.File to somehow wrap their files in a new wrapper class that implements the interface.  

So I'd be very open to hearing suggestions for this. Forcing clients to wrap java.io.File in some other interface would seem to be very inefficient. Though I do have some ideas, I guess.