code: void addAllForOTreeSet(SortedSet<? extends K> set, V defaultVal) {
      try {
        buildFromSorted(set.size(), set.iterator(), null, defaultVal);
      } catch (java.io.IOException cannotHappen) {
      } catch (ClassNotFoundException cannotHappen) {
      }
    }
docs: Intended to be called only from OTreeSet.addAll