In object-oriented programming, we can use inheritance when we know there is an “is a” relationship between a child and its parent class. Some examples would be: A person is a human.

The main thing to keep in mind is that polymorphism requires an inheritance or an interface implementation. You can see this in the example below, featuring Duke and Juggy: ...

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.