code: @Override
      public int compareTo(YearWeek other) {
          int cmp = (year - other.year);
          if (cmp == 0) {
              cmp = (week - other.week);
          }
          return cmp;
      }
docs: Compares this year-week to another
  <p>
  The comparison is based first on the value of the year, then on the value of the week.
  It is "consistent with equals", as defined by {@link Comparable}.
  
  @param other  the other year-week to compare to, not null
  @return the comparator value, negative if less, positive if greater