Why do you assign an objects to an interface?

Question

I have heard several times that when instantiating objects you should do:

\"Interface\" name = new \"Class\"();

For example for the class linkedlist that imp

Answer 1

This isn't as simple as it looks. If you use:

List name = new LinkedList();

if you ever wanted to switch from linked lists to arraylists it would be less maintenance.

About the redundancy, List name = new LinkedList() declares name of type List and invokes the LinkedList constructor. You could have as follows:

List name = someRandomObject.someRandomHelperMethod();

This helper method "just happens" to return a list, so there is no redundancy.

With Java 7 the apparently-redundant generic args can be skipped:

List someL = new ArrayList<>();

as opposed to

List someL = new ArrayList();