Multiset<String> result = TreeMultiset.create(NullsBeforeB.INSTANCE);
                    Collections.addAll(result, elements);
                    return result;
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    sort(insertionOrder, NullsBeforeB.INSTANCE);
                    return insertionOrder;
                  }

    }

    @Override
    public int hashCode() {
      return justAfterNull.hashCode();
    }
  }

  public static final class NullsBeforeB extends NullsBefore {
    public static final NullsBeforeB INSTANCE = new NullsBeforeB();

    private NullsBeforeB() {
      super("b");
    }
  }

  public static final class NullsBeforeTwo extends NullsBefore {