protected List<Pair<String, String>> createQuery(Random rndGen) {
    if (rndGen.nextInt(2) == 0) {
      return null;
    } else {
      List<Pair<String, String>> query = new ArrayList<Pair<String, String>>();

      int size = rndGen.nextInt(5);

      for (int i = 0; i < size; i++) {
        query.add(
            new Pair<String, String>(
                Util.createSimpleRandomString(rndGen, rndGen.nextInt(10) + 1, 'a', 'z'),
                Util.createComplexRandomString(rndGen, rndGen.nextInt(30))));
      }

      return query;
    }
  }
 public ComplexType(Random r) {
   name = Util.createSimpleRandomString(r, 10);
   age = r.nextInt(80);
 }