Java List vs ArrayList

Question

As a C++ oldtimer I have managed to solve my problem but I can not wrap my head around the underlying Java mechanisms here:

Vector<Object> x = new Vector<Object>();        // OK
ArrayList<Object> y = new ArrayList<Object>();  // OK
List<Object> zzz = new ArrayList<Object>();     // OK solves problem below but question remains
List<Object> z = new List<Object>();            // WHY? Compiler error: Cannot instantiate 

Answer 1

The List is an interface. You cannot create in instance of an interface using new operator. That's why the line List<Object> z = new List<Object>(); gives error. Only classes can be instantiated.

Answer 2

Yes. Because List is an Interface and in Java you cannot instantiate an Interface. You can only instantiate a class.

ArrayList is a class that's implementing List<> that's why you can instantiate it. :)