Java - how can I use interface outside my package in class in the package?

I have a class within a package that test if an interface is implemented in a class, but the problem is that the interface is not in the package and therefore I cant compile. (Its an assignment and the interface is not allowed to be moved into the package to solve this).

Can I somehow use the interface in the class in the package with the interface outside the package? (The interface and the package will be in the same directory)