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

ArrayList a = new ArrayList(); 

Does not work because the fact that Number is a super class of Integer does not mean that List is a super class of List. Generics are removed during compilation and do not exist on runtime, so parent-child relationship of collections cannot be be implemented: the information about element type is simply removed.

ArrayList a1 = new ArrayList