Why use a wild card capture helper method?

Question

Referring to : Wildcard Capture Helper Methods

It says to create a helper method to capture the wild card.

public void foo(List i) {
    fo         


        

Answer 1

I agree: Delete the helper method and type the public API. There's no reason not to, and every reason to.

Just to summarise the need for the helper with the wildcard version: Although it's obvious to us as humans, the compiler doesn't know that the unknown type returned from l.get(0) is the same unknown type of the list itself. ie it doesn't factor in that the parameter of the set() call comes from the same list object as the target, so it must be a safe operation. It only notices that the type returned from get() is unknown and the type of the target list is unknown, and two unknowns are not guaranteed to be the same type.