code: protected int handleGetMonthLength(int extendedYear, int month) {
          int thisStart = handleComputeMonthStart(extendedYear, month, true) -
              EPOCH_JULIAN_DAY + 1; // Julian day -> local days
          int nextStart = newMoonNear(thisStart + SYNODIC_GAP, true);
          return nextStart - thisStart;
      }
docs: Override Calendar method to return the number of days in the given
  extended year and month.
  
  <p>Note: This method also reads the IS_LEAP_MONTH field to determine
  whether or not the given month is a leap month.