code: public int[] getTags() {
          int[] tags = new int[fieldIndex.size()];
          Enumeration e = fieldIndex.keys();
          int i = 0;
          
          while (e.hasMoreElements()) {
              tags[i++] = ((Integer)e.nextElement()).intValue();
          }
          
          return tags;
      }
docs: Returns an ordered array of ints indicating the tag
  values.