/*
   *  listTermVectors displays the term vectors for all of the fields
   *  in a document in an index (specified by reader).
   */
  static void listTermVectors(IndexReader reader, String docidString) throws IOException {

    System.out.println("\nTermVector:  docid " + docidString);

    int docid = Integer.parseInt(docidString);

    if ((docid < 0) || (docid >= reader.numDocs())) {
      System.out.println("ERROR:  " + docidString + " is a bad document id.");
      return;
    }
    ;

    /*
     *  Iterate over the fields in this document.
     */
    Fields fields = reader.getTermVectors(docid);
    Iterator<String> fieldIterator = fields.iterator();

    while (fieldIterator.hasNext()) {
      String fieldName = fieldIterator.next();
      System.out.println("  Field: " + fieldName);

      Terms terms = fields.terms(fieldName);
      termVectorDisplay(terms);
    }
    ;
  }