Nothing really stopping you. You would have to set your an access level of "protected" or "public" if you want the subclass to be able to access the inherited attributes/methods
It's a good line of questioning! Read into Uncle Bob's OO Principles. The last few are about "packages." While he doesn't necessarily mean "Java packages" the concepts are very good and can be applied to packages or larger components and subsystems.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
Don't get me started about those stupid light bulbs.