code: public boolean containsAll(Collection<?> c) {
          if (!(c instanceof JumboEnumSet))
              return super.containsAll(c);
  
          JumboEnumSet<?> es = (JumboEnumSet<?>)c;
          if (es.elementType != elementType)
              return es.isEmpty();
  
          for (int i = 0; i < elements.length; i++)
              if ((es.elements[i] & ~elements[i]) != 0)
                  return false;
          return true;
      }
docs: Returns <tt>true</tt> if this set contains all of the elements
  in the specified collection.
  
  @param c collection to be checked for containment in this set
  @return <tt>true</tt> if this set contains all of the elements
  in the specified collection
  @throws NullPointerException if the specified collection is null