how Interface supports polymorphism?

[kiran nyala]

hi

i understand that an interface can implement by any number of classes so that we can say that interface supports polymorphism.
is my view correct?

Why we assign subclass object to super class reference in case of class inheritance and also in case of interface implementation? could you please explain

[Wouter Oet]

Please use text colouring only for highlighting.

[Jesper de Jong]

Your second question is a frequently asked question on the forums here. Look at the following example:

// Why would you want to write this:
List<String> names = new ArrayList<String>();

// Instead of this:
ArrayList<String> names = new ArrayList<String>();

The good thing about the first version is that the rest of the application that uses the list does not need to know what kind of list exactly it is - the only thing that's important is that it is a list. Because of this, you could easily change the exact type of the list if you later find out that that would be more efficient, for example:

List<String> names = new LinkedList<String>();

For the rest of the application, names is still a List<String>, so you would not have to change anything in the rest of the application.

It's the principle of program to an interface, not an implementation.