Java generics - ArrayList initialization

Question

It is known that arraylist init. should be like this

ArrayList a = new ArrayList();
ArrayList a = new ArrayList

        

Answer 1

Think of the ? as to mean "unknown". Thus, "ArrayList" is to say "an unknown type that (or as long as it)extends Object". Therefore, needful to say, arrayList.add(3) would be putting something you know, into an unknown. I.e 'Forgetting'.