Findbugs identifies 2 places:
FI: Finalizer nulls fields (FI_FINALIZER_NULLS_FIELDS)
This finalizer nulls out fields. This is usually an error, as it does not aid garbage collection, and the object is going to be garbage collected anyway.
FI: Finalizer only nulls fields (FI_FINALIZER_ONLY_NULLS_FIELDS)
This finalizer does nothing except null out fields. This is completely pointless, and requires that the object be garbage collected, finalized, and then garbage collected again. You should just remove the finalize method.