獲取本周第一天和最后一天，按周一至周日計算

/**
 * 獲取本周的第一天
 * @return String
 * **/
public static String getWeekStart(){
    Calendar cal=Calendar.getInstance();
    cal.setFirstDayOfWeek(Calendar.MONDAY);
    cal.setTime(new java.util.Date());
    cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek()); // Monday
    java.util.Date time=cal.getTime();
    return new SimpleDateFormat("yyyy-MM-dd").format(time)+" 00:00:00";
}

/**
 * 獲取本周的最后一天
 * @return String
 * **/
public static String getWeekEnd(){
    Calendar cal=Calendar.getInstance();
    cal.setFirstDayOfWeek(Calendar.MONDAY);
    cal.setTime(new java.util.Date());
    cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek() + 6); // Sunday
    java.util.Date time=cal.getTime();
    return new SimpleDateFormat("yyyy-MM-dd").format(time)+" 23:59:59";
}