milliseconds until next 5th second

So I want to do some monitoring and I want it to be on every fifth minute, so for example if the application starts at 1:47 monitor everything until 1:50 and then reset. I currently have this working for hour but I need to cut it down to every fifth minute and I'm having a little trouble coming up with the math.

I get all of the current time information

  Calendar currentCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
  long currentTimeInMillis = current开发者_高级运维Calendar.getTimeInMillis();
  int hr = currentCalendar.get(Calendar.HOUR_OF_DAY);
  int min = currentCalendar.get(Calendar.MINUTE);
  int sec = currentCalendar.get(Calendar.SECOND);
  int millis = currentCalendar.get(Calendar.MILLISECOND);

Now I need to find the next fifth minute, for hour I have this which works.

  millisUntilNextHour = currentTimeInMillis + ((60L - min) * SECONDS_IN_MINUTE * 1000L) + ((60 - sec) * 1000L) + (1000L - millis);

Can anybody think of a way similar to above to get the milliseconds to the closest fifth minute?

Every fifth minute is 5 minutes * 60 seconds/minute * 1000 millisecond/second = 300,000 milliseconds.

Try this then:

millisUntilNextHour = (min*60*1000 + sec*1000 + millis + 299999)/300000*300000 - (min*60*1000 + sec*1000 + millis)

The +299999)/300000*300000 rounds up to the nearest 300,000. Then you get the difference between that and the current millisecond to find out how many milliseconds you are away from it.

Using the same approach as described in the question:

 Calendar currentCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
 int min = currentCalendar.get(Calendar.MINUTE);
 currentCalendar.set(Calendar.MINUTE, 5 * (min / 5 + 1));
 currentCalendar.set(Calendar.SECOND, 0);
 currentCalendar.set(Calendar.MILLISECOND, 0);

 millisUntilNextHour = currentCalendar.getTimeInMillis();

Update: Reverted to my initial variant. It works as a charm. Lenient calendar (currentCalendar is lenient) works perfectly as expected when setting as minutes value greater than 60. From javadoc:

/**
 * With lenient interpretation, a date such as "February 942, 1996" will be
 * treated as being equivalent to the 941st day after February 1, 1996.
 * With strict (non-lenient) interpretation, such dates will cause an exception to be
 * thrown. The default is lenient.
 */

Why not use Quartz, which can handle this sort of thing easily. For the above you could specify a cron-type expression.

It may seem a bit heavyweight for your initial requirements but it's scaleable so it'll handle any future requirements.

Add five minutes to the current time, then set the seconds and millis to zero.

Note that the important thing is to use the .add(field, amount) method, as it will roll correctly into the next hour, etc. (including daylight savings, etc).

 Calendar currentCalendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
 // store off the milliseconds from the epoch
 int startTime = currentCalendar.getTime().getTime();
 currentCalendar.add(Calendar.MINUTE, 5);
 currentCalendar.set(Calendar.SECOND, 0);
 currentCalendar.set(Calendar.MILLISECOND, 0);

 // calculate the milliseconds difference.
 int difference = currentCalendar.getTime().getTime() - startTime;
 System.out.println("The number of milliseconds till " + currentCalendar.getTime() + " is " + startTime);