code: public static <E, S extends Set<E>> SynchronizedMutableSet<E> of(S set)
      {
          return new SynchronizedMutableSet<E>(SetAdapter.adapt(set));
      }
docs: This method will take a MutableSet and wrap it directly in a SynchronizedMutableSet.  It will
  take any other non-GS-collection and first adapt it will a SetAdapter, and then return a
  SynchronizedMutableSet that wraps the adapter.