Java using generics with lists and interfaces

Question

Ok, so here is my problem:

I have a list containing interfaces - List a - and a list of interfaces that extend that interface: Li

Answer 1

There's no way to do it that is type safe.

A List cannot have arbitrary Interfaces added to it. It is a list of SubInterfaces after all.

If you are convinced that this is safe to do even though it is not type safe you can do

@SuppressWarnings("unchecked")
void yourMethodName() {
  ...
  List a = (List) b;
  ...
}