How about something like Final by Default about nopen HOT 4 CLOSED

If it's not @Open or abstract though then what is it? Isn't final all that's left?

from nopen.

Fair point. Just avoiding the keyword final. It should be declared @Open or abstract. In the current check Non-final, Non-abstract classes without the @Open annotation will be marked with an error.. How about just treating them as final. All things are final by default and you have to mark @Open to make it subclassable.

from nopen.

That still allows their subclassing by downstream libraries. I suppose if the type isn't effectively public then perhaps the check shouldn't apply?

from nopen.

Oh. Didn't think of this use case.

from nopen.