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 ...

When to use inheritance in Java When to use composition in Java Differences between inheritance and composition Method overriding with Java inheritance Using constructors with inheritance Type ...

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