What is the meaning of!?

Question

- An abstract class cannot be instantiated

Answer 1

It simply means that you cannot create an object of that abstract class type but you can use it as a reference to create an object of the concrete class extending it.

More discussions on abstract classes.
https://www.sololearn.com/discuss/2092438/?ref=app
https://www.sololearn.com/discuss/2123978/?ref=app