通过Calendar来取星期几
//weekOfMonth = 0为当周；dayOfWeek = 1 为本周第一天；以此类推
public static Date getWeekDay(int weekOfMonth, int dayOfWeek) throws ParseException {
Calendar cal = Calendar.getInstance();
cal.add(Calendar.WEEK_OF_MONTH, weekOfMonth);
cal.set(Calendar.DAY_OF_WEEK, dayOfWeek);
return DateUtils.parseDate(DateFormatUtils.format(cal, "yyyy-MM-dd"), new String[] {"yyyy-MM-dd"});
}