爪哇 如果日期在 11 月的第一个星期日之前，我如何获得

Question

我正在做一个复合 if 语句来计算某个日期是否是夏令时日期，但是在试图找到一种方法来计算该日期是在 11 月的第一个星期日之前还是之后时，我陷入了困境。有人可以帮助我吗？这是我现在的代码：

public class Lab5 {
/**
* Return true if the given date/time is daylight savings.
* Daylight savings time begins 2am the second Sunday of March and ends 2am the first     Sunday of November.
* 
* @param month - represents the month with 1 = January, 12 = December
* @param date - represents the day of the month, between 1 and 31
* @param day - represents the day of the week with 1 = Sunday, 7 = Saturday
* @param hour - represents the hour of the day with 0 = midnight, 12 = noon
* 
* Precondition: the month is between 1 and 12, the date is between 1 and 31, the day is between 1 and 7
*                and the hour is between 0 and 23.
*/
public static boolean isDayLightSavings (int month, int date, int day, int hour) {
  if (month == 1 || month == 2 || month == 12)
    return false;
  else if (month == 11) {
    if (day == 1 && hour < 2 && date < 8)
      return true;
    else            
      return false;
  }
  else
    return true;    
 }
}

编辑：我相信我的问题还不够清楚。我知道如何找到十一月的第一个星期日

else if (month == 11) {
if (day == 1 && hour < 2 && date < 8)

我似乎无法做的是确定我的日期是在十一月的第一个星期日之前还是之后。我需要使用 if 语句来做到这一点，而不是预加载的库、方法或类。

Answer 1

请参阅我的内联评论

public class Lab5 {
/**
* Return true if the given date/time is daylight savings.
* Daylight savings time begins 2am the second Sunday of March and ends 2am the first     Sunday of November.
* 
* @param month - represents the month with 1 = January, 12 = December
* @param date - represents the day of the month, between 1 and 31
* @param day - represents the day of the week with 1 = Sunday, 7 = Saturday
* @param hour - represents the hour of the day with 0 = midnight, 12 = noon
* 
* Precondition: the month is between 1 and 12, the date is between 1 and 31, the day is between 1 and 7
*                and the hour is between 0 and 23.
*/
public static boolean isDayLightSavings (int month, int date, int day, int hour) {
  if (month == 1 || month == 2 || month == 12)
    return false;
  else if (month == 11) {
    if (date > 7)  // after 7th, it would be second week'day' of the month
      return false;
    else if ((date - day) >= 0) { 
      // As we ruled out all dates above 7, we would get only 1-7
      // here. Now, lets take 3rd as Monday, date == 3, day == 2
      // so we know that 2 is Sunday. that means if date - day is positive or zero,
      // Sunday is already past. one border case is, when Sunday falls on the date entered and we
      // we need to consider the first 2 hours of the day
      if((day == 1) && (hours < 2))
        return true;
      else
        return false;
    }
    else {
      // we will come here if date - day is less than zero
      // example, 3rd came on Thursday, 3 - 5 = -2 and so
      // first sunday is not yet past
      return true;
    }            
  }
  else
    return true;    
 }
}

Answer 2

与其重新发明轮子，我建议您使用 joda time ，它考虑了夏令时 （DST）。

http://joda-time.sourceforge.net/faq.html