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

Get started with polymorphism in Java and how to do method invocation in polymorphic method calls.

Sealed classes in Java let developers limit the creation and use of subclasses and preserve the class hierarchy. Here is how sealed classes in Java work.

The original definition uses the word extension, which in Java implies inheritance. However, inheritance isn't the best way to implement the open-closed principle in Java. Open-closed principle ...