Use Java's extends keyword to derive a child class from a parent class, invoke parent class constructors and methods, override methods, and more.

Polymorphism in method overriding. It’s possible to change the return type of an overridden method if it is a covariant type. A covariant type is essentially a subclass of the return type. Here ...

Sealed classes make Java an even more powerful and expressive language and set the stage for even more sophisticated techniques such as pattern matching, which we'll explore in a subsequent article. A ...