Why not fix Java to have compile-time checked not-null types? Given that not-null is a strict subset of nullable, it wouldn't break code to annotate the standar

Why not fix Java to have compile-time checked not-null types? Given that not-null is a strict subset of nullable, it wouldn't break code to annotate the standard library with not-nulls. Then we can avoid these run-time checks entirely. Oh and while you're about it, please re-parent InterruptedException onto RuntimeException, and make Object's default toString method use reflection to print the contents of all fields in a readable format with recursive toString calls.