Covariance, Invariance, and Contravariance in Java: What's the Difference and Why Should I Care?

Covariance, Invariance, and Contravariance Explained in Plain English

Introduction:
Understanding covariance, invariance, and contravariance can be challenging, but it's essential for comprehending type transformations and relationships in Java. This article aims to simplify these concepts and provide real-world examples to enhance understanding.

Covariance:
Covariance describes a type transformation where the subtype relation is preserved. If type A is a subtype of type B, then the transformation f(A) will result in f(B) being a subtype of f(A).

Example:
Consider a transformation f(List) = List