日期计算工具类：根据时间区间获取中间间隔了多少周，输出每周的第一天和最后一天

话不多说，直接上代码

计算周期内间隔多少周，返回数字

 /**
     * 根据时间区间获取中间间隔了多少周
     * @param startDate
     * @param endDate
     * @return
     */
    public static Long getNumOfWeek(Date startDate, Date endDate) {
        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();

        c1.setTime(startDate);
        c2.setTime(endDate);

        long cc1 = From(c1).getTimeInMillis() / (1000 * 3600 * 24);
        long cc2 = To(c2).getTimeInMillis() / (1000 * 3600 * 24);

        return (cc2 - cc1 + 1) / 7;
    }

获取每周的第一天和最后一天

public List<WeekEntity> getTimeList(){
	Long numWeek = this.getNumOfWeek(Date date1,Date date2);
	List<WeekEntity> weekList=new ArrayList();
	 //遍历数据获取每周的第一天和最后一天
	for (int i = 0; i < numWeek; i++) {
	    //根据日期获取当前周的数据列表
	    List<Date> dateList = this.getDateListOfWeek(i, date1);
	
	    WeekEntity week = new WeekEntity ();
	    week.setStartDate(dateList.get(0));
	    week.setEndDate(dateList.get(dateList.size() - 1));
	    weekList.add(week);
	}
	 return conditionBOList;
}

计算开始时间的日期

 private static Calendar From(Calendar c) {
        switch (calculate(c)) {
            case 1:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 0);
                break;
            case 2:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 1);
                break;
            case 3:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 2);
                break;
            case 4:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 3);
                break;
            case 5:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 4);
                break;
            case 6:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 5);
                break;
            case 7:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) - 6);
        }
        return c;

    }

计算结束时间的日期

private static Calendar To(Calendar c) {
        switch (calculate(c)) {
            case 1:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 6);
                break;
            case 2:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 5);
                break;
            case 3:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 4);
                break;
            case 4:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 3);
                break;
            case 5:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 2);
                break;
            case 6:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 1);
                break;
            case 7:
                c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 0);
        }
        return c;

    }

日期计算工具

private static int calculate(Calendar c) {
        int dayForWeek;
        if (c.get(Calendar.DAY_OF_WEEK) == 1) {
            dayForWeek = 7;
        } else {
            dayForWeek = c.get(Calendar.DAY_OF_WEEK) - 1;
        }
        return dayForWeek;
    }

获取当前周的所有日期

 /**
     * 获取当前周的所有日期
     *
     * @param n      -1代表上一周 +1代表下一周
     * @param myDate 当前日期
     */
    public static List<Date> getDateListOfWeek(int n, Date myDate) {
        List<Date> date = new ArrayList<Date>();
        try {
            Calendar calendar = Calendar.getInstance();
            calendar.setFirstDayOfWeek(Calendar.MONDAY);
            Calendar cal = Calendar.getInstance();
            cal.setTime(myDate);
            //判断要计算的日期是否是周日，如果是则减一天计算周六的，否则会出问题，计算到下一周了，获得当前日期是一个星期的第几天
            int dayWeek = cal.get(Calendar.DAY_OF_WEEK);
            if (1 == dayWeek) {
                cal.add(Calendar.DAY_OF_MONTH, -1);
            }
            //设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
            cal.setFirstDayOfWeek(Calendar.MONDAY);
            //获得当前日期是一个星期的第几天
            int day = cal.get(Calendar.DAY_OF_WEEK);
            //根据日历的规则，给当前日期减去星期几与一个星期第一天的差值
            cal.add(Calendar.DATE, (cal.getFirstDayOfWeek() - day + 7 * n));
            date.add(cal.getTime());
            for (int i = 1; i < 7; i++) {
                cal.add(Calendar.DATE, 1);
                date.add(cal.getTime());
            }

        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
        return date;
    }