What do you call the superclass and subclass when initializing? [duplicate]

Answer 1

Difference:

• First one, Only methods of the interface List can be invoked on the list object. polymorphisme is present here.
• Second one, methods of ArrayList class can be invoked on the list object.

Advantages of the first one:

Even if you change the implementation to:

List list = new LinkedList();

or

List list = new Vector();

You have not to change the rest your code.