Rounding up milliseconds when printing with Joda Time

Question

I'm implementing a count-down using Joda Time. I only need a display accuracy of seconds.

However when printing the time, the seconds are displayed as full seconds, so when the count down reaches, for example, 900ms, then "0" seconds is printed, but as a count-down it would make more sense to display "1" second, until the time actually reaches 0ms.

Example:

void printDuration(Duration d) {
  System.out.println(
    d.toPeriod(PeriodType.time()).toString(
      new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter()
    )
  );
}

printDuration(new Duration(5000)); // Prints "5" => OK
printDuration(new Duration(4900)); // Prints "4" => need "5"
printDuration(new Duration(1000)); // Prints "1" => OK
printDuration(new Duration(900));  // Prints "0" => need "1"
printDuration(new Duration(0));    // Prints "0" => OK

Basically I need to the seconds to be display rounded up from milliseconds and not rounded down. Is there a way to achieve this with Joda without needing to write my own formatter?

Answer 1

The simplest way would be to take the existing duration, round the milliseconds appropriately to create a new duration, and format that:

private static Duration roundToSeconds(Duration d) {
  return new Duration(((d.getMillis() + 500) / 1000) * 1000);
}

(Note that this assumes positive durations, otherwise the rounding will be odd.)

Answer 2

Are you interested in printing only durations of a few seconds ?

If not, your printDuration method is wrong (it prints 0 for Duration(60000) - ie, prints only the seconds fractions)

(BTW, it makes me uncofortable to see that formatter instantiated in each call)

If yes, (or if you are satisfied with printing "3600" for a Duration of one hour) you actually don't need time intelligence, it would be more simple to do the formatting yourself:

static void printDuration(Duration d) {
      int secs = (int)((d.getMillis()+999)/1000); 
      System.out.println(secs);
}

As Jon points out, this only makes sense for positive durations.

Answer 3

import java.math.BigDecimal;

private Duration round(Duration d) {
  return Duration.standardSeconds(new BigDecimal(d.getMillis()).divide(1000, 0, BigDecimal.ROUND_up));
}

and then:

void printDuration(Duration d) {
    System.out.println(
        round(d).toPeriod(PeriodType.time()).toString(
            new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter()
        )
    );
}