Method next

src/main/java/com/nlf/calendar/SolarWeek.java:191–235

周推移 @param weeks 推移的周数，负数为倒推 @param separateMonth 是否按月单独计算 @return 推移后的阳历周

(int weeks, boolean separateMonth)

   * @return 推移后的阳历周
   */
  public SolarWeek next(int weeks, boolean separateMonth) {
    if (0 == weeks) {
      return new SolarWeek(year, month, day, start);
    }
    Solar solar  = Solar.fromYmd(year, month, day);
    if (separateMonth) {
      int n = weeks;
      SolarWeek week = new SolarWeek(solar.getYear(), solar.getMonth(), solar.getDay(), start);
      int month = this.month;
      boolean plus = n > 0;
      while (0 != n) {
        solar = solar.next(plus ? 7 : -7);
        week = new SolarWeek(solar.getYear(), solar.getMonth(), solar.getDay(), start);
        int weekMonth = week.getMonth();
        if (month != weekMonth) {
          int index = week.getIndex();
          if (plus) {
            if (1 == index) {
              Solar firstDay = week.getFirstDay();
              week = new SolarWeek(firstDay.getYear(), firstDay.getMonth(), firstDay.getDay(), start);
              weekMonth = week.getMonth();
            } else {
              solar = Solar.fromYmd(week.getYear(), week.getMonth(), 1);
              week = new SolarWeek(solar.getYear(), solar.getMonth(), solar.getDay(), start);
            }
          } else {
            if (SolarUtil.getWeeksOfMonth(week.getYear(), week.getMonth(), start) == index) {
              Solar lastDay = week.getFirstDay().next(6);
              week = new SolarWeek(lastDay.getYear(), lastDay.getMonth(), lastDay.getDay(), start);
              weekMonth = week.getMonth();
            } else {
              solar = Solar.fromYmd(week.getYear(), week.getMonth(), SolarUtil.getDaysOfMonth(week.getYear(), week.getMonth()));
              week = new SolarWeek(solar.getYear(), solar.getMonth(), solar.getDay(), start);
            }
          }
          month = weekMonth;
        }
        n -= plus ? 1 : -1;
      }
      return week;
    } else {
      solar = solar.next(weeks * 7);
      return new SolarWeek(solar.getYear(), solar.getMonth(), solar.getDay(), start);
    }
  }

  /**
   * 获取本周第一天的阳历日期（可能跨月）