This is the second part of our exploration into co- and contravariance. In part one, we covered the basic concepts and intuitions behind variance in type systems. Hopefully it already helped you to gain better understanding in the various co- and contravariance concepts. If you still struggle and change minusses to plusses or vice versa (or super to extend clauses) then this second part is for you.
With a simple example, the concept of co- and contravariance is understood. Forever and for everybody! With examples for scala and java developers.