It’s a good idea to use an abstract class when you need to implement mutable state. As an example, the Java Collections Framework includes the AbstractList class, which uses the state of variables.

That means you cannot create new instances of an abstract class. It works as a base for subclasses. You should learn about Java Inheritance before attempting this challenge. Following is an example of ...

In Java Abstraction is achieved using Abstract classes and Interface.An abstract class is a class which is incomplete. You cannot create an instance of an abstract class in Java. They are provided to ...