Why is List not simply defined as an abstract class rather than being an interface?

Question

We have something like

List lst = new LinkedList();

which shows that List is some sort of Class. So, why call it an Interface? We can simply call it an Abstract class which implements Collection.

Answer 1

Interfaces and Abstract classes are used for different purposes. See this question.

A List defines a set of behaviour we want list-type objects to have, not the basis for a hierarchy of data structures. It doesn't need to specify any shared behaviour or anything like that. It just has the simple job of saying "everything that wants to call itself a List should be able to do these things"