There are three major features in object-oriented programming that makes them different than non-OOP languages: encapsulation, inheritance and polymorphism. Encapsulation Enforces Modularity ...

Learn the four types of polymorphism in Java, then start using subtype polymorphism to execute different forms of the same Java method.

Compare inheritance and composition, the two fundamental ways to relate Java classes, then practice debugging ClassCastExceptions in Java inheritance.