// Replace immutable empty list with mutable list.
          extras = new ArrayList<>();
        }
        extras.add(other.element);
        extras.addAll(other.extras);
        if (extras.size() > MAX_EXTRAS) {
          extras.subList(MAX_EXTRAS, extras.size()).clear();
          throw multiples(true);
        }
        return this;
      }
    }

      int minCopiesOfEachGoodQuery = numGoodQueries / size;
      int extras = numGoodQueries % size;

      for (int i = 0; i < minCopiesOfEachGoodQuery; i++) {
        queryList.addAll(elementsInSet);
      }
      List<Element> tmp = Lists.newArrayList(elementsInSet);
      Collections.shuffle(tmp, random);
      queryList.addAll(tmp.subList(0, extras));
    }

    // now add bad queries

      int minCopiesOfEachGoodQuery = numGoodQueries / size;
      int extras = numGoodQueries % size;

      for (int i = 0; i < minCopiesOfEachGoodQuery; i++) {
        queryList.addAll(elementsInSet);
      }
      List<Element> tmp = Lists.newArrayList(elementsInSet);
      Collections.shuffle(tmp, random);
      queryList.addAll(tmp.subList(0, extras));
    }

    // now add bad queries