Any way to convert a JodaTime Period to a decimal number of hours?

Question

I have a JodaTime Period that I've created from two DateTime instants. Is there a good way to convert that Period into a decimal number of hours?

For instance, I have a Period that goes from 1pm to 1:30pm on Jan 1, 2010. How can I get that Period as 1.5 hours.

In the past I've manually converted using seconds and BigDecimals such as this:

int seconds = myPeriod.toStandardSeconds().getSeconds();
BigDecimal d = new BigDecimal((double) seconds / 3600);
// Round to two decimals
BigDecimal correctResult = d.setScale(2, RoundingMode.HALF_DOWN);

This kind of feels like a hack, not to mention awkward when I start adding Periods together. It seems like there should be a better way.

Any ideas? Thanks

Answer 1

A bit old but I was looking at this recently and you can use the DateTimeFormatterBuilder to do this. It has a series of methods called appendFraction... which will append a fraction of an hour, minute, second etc.

This is not exactly what you were asking as you were using a Period but you can work around this by making a new DateTime at midnight.

This formatter should parse your DateTime:

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
    .appendHourOfDay(1)
    .appendLiteral(".")
    .appendFractionOfHour(1, 2).toFormatter();

You could then do something like this to convert your period:

    DateMidnight midnight = new DateTime("2012-12-13T21:39:45.618").toDateMidnight();
    LocalTime localTime = new LocalTime(midnight);
    localTime.plus(period);
    formatter.print(localTime);

Answer 2

Using the Jon Skeet example, you have a Non-terminating decimal expansion Exception from divide BigDecimal divide(MILLIS_PER_HOUR), for fix error alter code for this:

private static final BigDecimal MILLIS_PER_HOUR = 
    BigDecimal.valueOf(DateTimeConstants.MILLIS_PER_HOUR);




    DateTime t = new DateTime();
    DateTime t1 = new DateTime();
    DateTime dt1 = t;
    DateTime dt2 = t1.plusMinutes(46); 
    Duration duration = new Duration(dt1, dt2);
    BigDecimal result = BigDecimal.valueOf(duration.getMillis())
                          .divide(MILLIS_PER_HOUR, 2, RoundingMode.CEILING) // <--- Add scale and RoundingMode.CEILING
                          .setScale(2); 

Answer 3

If you've got two DateTimes, I'd expect you to have a Duration between them rather than a Period... but other than that and Mike's comments, that looks correct:

private static final BigDecimal SECONDS_PER_HOUR = 
    BigDecimal.valueOf(DateTimeConstants.SECONDS_PER_HOUR);
...
DateTime dt1 = ...;
DateTime dt2 = ...;
Duration duration = new Duration(dt1, dt2);
BigDecimal result = BigDecimal.valueOf(duration.toStandardSeconds().getSeconds())
                              .divide(SECONDS_PER_HOUR)
                              .setScale(2, RoundingMode.HALF_DOWN);

Note that you can avoid the toStandardSeconds().getSeconds() using Duration.getMillis() instead:

private static final BigDecimal MILLIS_PER_HOUR = 
    BigDecimal.valueOf(DateTimeConstants.MILLIS_PER_HOUR);
...
DateTime dt1 = ...;
DateTime dt2 = ...;
Duration duration = new Duration(dt1, dt2);
BigDecimal result = BigDecimal.valueOf(duration.getMillis())
                              .divide(MILLIS_PER_HOUR)
                              .setScale(2, RoundingMode.HALF_DOWN);