code: @Override
    @SuppressFBWarnings(value = "EQ_COMPARETO_USE_OBJECT_EQUALS",
      justification = "OK for this use-case")
    public int compareTo(final Group that) {
      return that.count - count; //decreasing
    }
docs: Note: this class has a natural ordering that is inconsistent with equals.
  Ignore FindBugs warning on this issue.
  @param that the Group to compare to