Since marker interfaces do not contain methods, there's no implementation to point to. See
this FAQ entry for some more information on marker interfaces.
clone is defined in the Object class, but it is not part of the Cloneable interface. Cloneable merely governs whether clone may or may not be called. (That of course begs the question: why wasn't clone made part of Cloneable, and that interface implemented by all cloneable classes, instead of adding the method to the Object class?)
[ January 10, 2008: Message edited by: Ulf Dittmer ]