What is the benefit of polymorphism using Collection interface to create ArrayList object?

Question

I studied polymorphism and understand that it can do dynamic method binding like below.

Assuming that class Animal is abstract class.

public class An         


        

Answer 1

If you're declaring an ArrayList, I wouldn't ever use ArrayList as the type on the left side. Instead, program to the interface, be it List or Collection.

Note that if you declare a method as taking a Collection, it can be passed a List or Set.

As a side note, consider using Generics.

Edit: Having said that, Generics also introduces some Gotchas.

List could store an ArrayList, but not an ArrayList. You'd need List to store an ArrayList.