code: private void prepare(SolrParams solrParams, SortedSet<String> gids,
        String name, String[] positions, String[] prefixes) throws IOException {
      if (!gids.isEmpty()) {
        int tmpSubCounter = 0;
        for (String gid : gids) {
          positions[tmpSubCounter] = solrParams.get(
              name + "." + gid + "." + NAME_MTAS_GROUP_GROUPING_POSITION, null);
          prefixes[tmpSubCounter] = solrParams.get(
              name + "." + gid + "." + NAME_MTAS_GROUP_GROUPING_PREFIXES, null);
          if (positions[tmpSubCounter] == null) {
            throw new IOException("no position for " + gid);
          } else if (prefixes[tmpSubCounter] == null) {
            throw new IOException("no prefix for " + gid);
          }
          tmpSubCounter++;
        }
      }
    }
docs: Prepare.
  
  @param solrParams the solr params
  @param gids the gids
  @param name the name
  @param positions the positions
  @param prefixes the prefixes
  @throws IOException Signals that an I/O exception has occurred.