Covariant, Contravariant and Invariant (class invariant) in Java

Type variance is another feature which defines the flexibility in code writing every of programming language. Let me show you some of the variant type jargon's which explains the type variance.

When ever we are talking about type variance,

Programming with interface and programming to interface

Another good habit that every programmer adopt is programming to interfaces, rather than programming to implementations. It is clearly not about using interfaces in your application, though you are using interfaces at design level, it is very hard to make coders to get benefit out it. There is a very big difference between programming with interfaces and programming to interfaces. The main difference is that