Java: Rationale of the Object class not being declared abstract

Question

Why wasn\'t the java.lang.Object class declared to be abstract ?

Surely for an Object to be useful it needs added state or behaviour, an Object class is

Answer 1

I'll just throw in another reason that I've found Object to useful to instantiate on its own. I have a pool of objects I've created that has a number of slots. Those slots can contain any of a number of objects, all that inherit from an abstract class. But what do I put in the pool to represent "empty". I could use null, but for my purpose, it made more sense to insure that there was always some object in each slot. I can't instantiate the abstract class to put in there, and I wouldn't have wanted to. So I could have created a concrete subclass of my abstract class to represent "not a useful foo", but that seemed unnecessary when using an instance of Object was just as good..in fact better, as it clearly says that what's in the slot has no functionality. So when I initialize my pool, I do so by creating an Object to assign to each slot as the initial condition of the pool.

I agree that it might have made sense for the original Java crew to have defined a Placeholder object as a concrete subclass of Object, and then made Object abstract, but it doesn't rub me wrong at all that they went the way they did. I would then have used Placeholder in place of Object.