The JLS is more confusing than usual on this topic. Campbell summarizes it correctly - the supertypes and subtypes of a class include the class itself, but the superclasses and subclasses do not. Which seems stylistically inconsistent, but logically consistent, in the sense that the JLS
does use the terms precisely and consistently, even if they
seem inconsistent.
So if you're using the JLS definitions, a class is
not a subclass of itself, but it is a subtype of itself.
If you're using some other definitions, well, the answer would depend on the definitions used.