GregorianCalendar: Jumping from Tuesday to Sunday
I have a GregorianCalendar instance for Tuesday September 2nd. The badge is checked in milliseconds and is ok. I want another calendar to be next Sunday (7) at 23:59:59. So:
GregorianCalendar currentCalendar = MyClock.INSTANCE.getCurrentCalendar();
GregorianCalendar nextSunday =
(GregorianCalendar)currentCalendar.clone();
// GregorianCalendar uses Sunday as first day of week, so we must
// advance one week
int currentWeek = nextSunday.get(GregorianCalendar.WEEK_OF_YEAR);
nextSunday.set(GregorianCalendar.WEEK_OF_YEAR,
currentWeek + this.THIS_WEEK);
nextSunday.set(GregorianCalendar.DAY_OF_WEEK, GregorianCalendar.SUNDAY);
nextSunday.set(GregorianCalendar.HOUR_OF_DAY, 23);
nextSunday.set(GregorianCalendar.MINUTE, 59);
nextSunday.set(GregorianCalendar.SECOND, 59);
nextSunday.set(GregorianCalendar.MILLISECOND, 0);
So, since Sunday is day # 1 of the week for GregorianCalendar and I am in week of year 36, I add one week and then set the day to Sunday.
The real problem is now: when running on my development machine with OpenJDK 1.7.0_55, it works fine. If I go to my test machine with OpenJDK 1.7.0_51, everything goes wrong:
Adds one week to day 9 and then ships on Sunday 14th instead of Sunday 7th.
I don't know if I'm doing it right or wrong: what really kills me is that the result is machine dependent, and I didn't find a difference in GregorianCalendar in these versions of OpenJDK. Any explanation for this behavior?
PD: Please stick to GregorianCalendar. I know, a little shitty, but I don't want to use Joda calendar or any other currently in development.
EDIT: I found the setWeekDate method (year, week_of_year, day_of_week). One would think that setting the year, week, and day of the week to the same method would give it success. It doesn't happen: it still goes from 2nd to 14th. What did the monkey write this?
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I changed your code a bit:
SimpleDateFormat sdf = new SimpleDateFormat("dd MM yyyy - HH:mm:ss.SSSS Z");
GregorianCalendar currentCalendar = (GregorianCalendar) Calendar.getInstance();
currentCalendar.set(Calendar.DAY_OF_MONTH, 2);
System.out.println(sdf.format(currentCalendar.getTime()));
GregorianCalendar nextSunday = (GregorianCalendar) currentCalendar.clone();
// GregorianCalendar uses Sunday as first day of week, so we must
// advance one week
int currentWeek = nextSunday.get(GregorianCalendar.WEEK_OF_YEAR);
nextSunday.set(GregorianCalendar.WEEK_OF_YEAR, currentWeek + 1);
nextSunday.set(GregorianCalendar.DAY_OF_WEEK, GregorianCalendar.SUNDAY);
nextSunday.set(GregorianCalendar.HOUR_OF_DAY, 23);
nextSunday.set(GregorianCalendar.MINUTE, 59);
nextSunday.set(GregorianCalendar.SECOND, 59);
nextSunday.set(GregorianCalendar.MILLISECOND, 0);
System.out.println(sdf.format(nextSunday.getTime()));
Output:
02 12 2014 - 19:40:46.0250 +0200
07 12 2014 - 23:59:59.0000 +0200
It is right. However, I have two reasons:
- check the value of this.THIS_WEEK. I replaced it with a value of 1 and it works fine on my machine.
- check timezone on both machines (GMT + 2 in my case). Since both machines use the same code that both initializes the values and uses them, there should be no problem. But if you use millisecond values on another computer (for example, expose the value through a web service or something else), you may run into problems.
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