The more familiar you are with Object and its methods, the more you can do with your Java programs.

The first half of this introduction to Java inheritance teaches you how to use the extends keyword to derive a child class from a parent class, invoke parent class constructors and methods, and ...

It's not good enough to simply use inheritance and apply the rules of polymorphism to your code. To write SOLID code, and properly implement the Liskov substitution principle in Java, your code must ...