Why can't we instantiate an abstract class in Java?

Question

I understand:

1. Since an abstract class is nothing on its own, e.g. vehicle, we want to create an object of an concrete implementation, like Car, Bike, etc.
2. The constructor of an abstract class gets called during object chaining.
3. We can never directly create an object of an abstract class, even if it contains a constructor and all methods are implemented.

But from the compiler's perspective, why does Java enforce these rules?

Answer 1

An abstract class is not complete! The author marked it abstract to tell you that some implementation is missing in the code. The author has done some of the work, but you must fill in some bits yourself to get it working. The abstract keyword ensures that no one would accidentally initiate this incomplete class.

Think of repairing a car. Someone has removed the brake pads and is going to replace them in the next day. Now, to prevent someone accidentally driving this car(which has no brakes installed), the mechanic installs a lock on the steering wheel. It's a fail-safe measure.

Answer 2

This is not a technical limitation, rather (as you have pointed out) a logical one. Java (and many other languages) enforce various rules not because they are impossible to break, but because this is an intentional part of the language.