code: public static int[] getSplit(int docId) {
          if (docId <= 0) {
              throw new IllegalArgumentException("docId must be positive");
          }
          int[] ret = new int[3];
          ret[0] = docId / 1000000;
          ret[1] = (docId % 1000000) / 1000;
          ret[2] = docId % 1000;
          return ret;
      }
docs: @param docId
  @return an array with 3 elements, the last 2 elements have 3 digits,
  e.g.:
  <ul>
  <li>2345678 -> {2, 345, 678}</li>
  <li>78 -> {0, 0, 78} (no leading 0es, just 78!)</li>
  </ul>