What is the difference between A and A<? extends B>?

Question

I am a new java learner. Recently I was reading Generic programming and got my self confused with this...

A and A
         


        

Answer 1

? is what is called a wildcard. It means anything that extends B.

When you write List, your List can contains only elements of type T.

When you write List, your List can contains any element that extends String

I hope I'm clear, since these concepts are complicated.