Convert duration to String in JodaTime

Question

I have a duration, e.g. like this:

PT-27900S = -27900000 milliseconds

and I want to convert this into a String with format (+/-HH:mm) Ich I convert the a negativ duration to String with:

final PeriodFormatter hoursAndMinutesFormatter = new PeriodFormatterBuilder()
                                                .printZeroAlways()
                                                .minimumPrintedDigits(2)
                                                .appendHours()
                                                .appendSeparator(":")
                                                .appendMinutes()
                                                .toFormatter();

I get e.g. this result:

-07:-45

but I want like this.

-07:45

Is there any possibility to format it like this?

Answer 1

Well, there is no format support in Joda-Time for the way you want to see negative durations. The nearest what I can see per documentation (indicated by the name) might be the method rejectSignedValues(). I have tested it in every possible configuration (inserted it at the begin, directly before appendMinutes(), directly behind, with the undocumented argument false or true in all cases), but it does not do anything in my tests (see updated side-note).

So there are logically only two options left:

a) Write this hack:

PeriodFormatter hoursAndMinutesFormatter = new PeriodFormatterBuilder()
.printZeroAlways()
.minimumPrintedDigits(2)
.appendHours()
.appendSeparator(":")
//.rejectSignedValues(true) // no effect ?!
.appendMinutes()
.toFormatter();     

long millis = -27900000;
Duration d =  new Duration(millis);
Period p = d.toPeriod();
String s;
if (millis < 0) {
    s = "-" + hoursAndMinutesFormatter.print(p.negated());
} else {
    s = hoursAndMinutesFormatter.print(p);
}

System.out.println("Joda-Time: " + s); // -07:45

b) Alternatively switch to another library which has better support for negative durations.

=> Example for built-in XML-duration which has better sign handling but no real formatter beyond XML-Schema compatible representation (although you are free to query the single components of duration and format it with let's say java.util.Formatter).

long millis = -27900000;
javax.xml.datatype.Duration xmlDuration = 
    DatatypeFactory.newInstance().newDuration(millis);
System.out.println("XML: " + xmlDuration.toString()); // -P0Y0M0DT7H45M0.000S
System.out.println(
    String.format(
        "%1$s%2$02d:%3$02d", 
        xmlDuration.getSign() < 0 ? "-" : "+", 
        xmlDuration.getHours(), 
        xmlDuration.getMinutes())); // -07:45

=> Or use my library Time4J which has a pattern-based duration formatter:

long millis = -27900000;
Duration<ClockUnit> duration = Duration.of(millis, ClockUnit.MILLIS); // create
duration = duration.with(Duration.STD_CLOCK_PERIOD); // normalization to hours and minutes
String s = Duration.formatter("-hh:mm").format(duration);
System.out.println("Time4J: " + s); // -07:45

---

Side notes:

1. The new Java-8 classes Duration and Period have the same sign handling as Joda-Time (preferring signs not in front but before every single component). You can see it when you watch the output of method toString(). Any special duration formatter is not offered.

2. The sign handling of Joda-Time is not compatible with XML-Schema v1.1 (look especially at the section: 3.3.6.2 Lexical Mapping).

3. Now I have found out what the method rejectSignedValues() is for. It is relevant for parsing only and just controls the exception behaviour (configurable via its boolean argument). However, parsing a value like "-07:45" would yield an unexpected millis-value different from your input (-22500000 != -27900000).