code: public long[] keySetLong() {
      long[] dom = new long[size()];
      IteratorLong i=(IteratorLong)keySet().iterator();
      int j=0;
      while( j < dom.length && i.hasNext() )
        dom[j++] = i.nextLong();
      return dom;
    }
docs: Keys as a long array.  Array may be zero-padded if keys are concurrently deleted.