code: public boolean addAll(Collection<? extends E> c) {
          if (!(c instanceof JumboEnumSet))
              return super.addAll(c);
  
          JumboEnumSet<?> es = (JumboEnumSet<?>)c;
          if (es.elementType != elementType) {
              if (es.isEmpty())
                  return false;
              else
                  throw new ClassCastException(
                      es.elementType + " != " + elementType);
          }
  
          for (int i = 0; i < elements.length; i++)
              elements[i] |= es.elements[i];
          return recalculateSize();
      }
docs: Adds all of the elements in the specified collection to this set.
  
  @param c collection whose elements are to be added to this set
  @return <tt>true</tt> if this set changed as a result of the call
  @throws NullPointerException if the specified collection or any of
  its elements are null