I am trying to parse durationString= P10YT10M using java.time.Duration.parse() method but its failing with "Text cannot be parsed to a Duration "

try {
    String durationString = "P5YT30M";
    Duration duration = Duration.parse(durationString);
} catch ( Exception e) {
    System.err.println( e.getMessage());

Its working for durationStrings like PT5M, but not able to parse durationStrings Similar to P5YT30M, P5Y8M4W3D

I am trying to parse durationString= P10YT10M using java.time.Duration.parse() method but its failing with "Text cannot be parsed to a Duration "

try {
    String durationString = "P5YT30M";
    Duration duration = Duration.parse(durationString);
} catch ( Exception e) {
    System.err.println( e.getMessage());

Its working for durationStrings like PT5M, but not able to parse durationStrings Similar to P5YT30M, P5Y8M4W3D

• java
• java-time
• duration
• iso8601

• 1 The PeriodDuration class of ThreeTen Extra can parse that string and similar strings. – Anonymous Commented 2 days ago

4 Answers 4

No, that text can't be parsed to a Duration. The documentation for Duration.parse is clear about what it will handle:

Obtains a Duration from a text string such as PnDTnHnMn.nS.

[...] There are then four sections, each consisting of a number and a suffix. The sections have suffixes in ASCII of "D", "H", "M" and "S" for days, hours, minutes and seconds, accepted in upper or lower case. The suffixes must occur in order.

P10YT10M isn't in that format, so it can't be parsed by Duration.parse. There's a good reason for this: a Duration is a fixed length of time (and the Duration.parse docs call out that parse treats a day as 24 hours). Years and months are not fixed lengths of time - should "P1M" be equivalent to 28 days? 29? 30? 31?

You can use Period.parse for non-time-based ISO durations, but that still won't handle P5YT30M for example. If you really need this, I'd suggest you:

• Split the input into "days and bigger" and "hours and smaller" (so basically at the T)
• Parse the days-and-bigger part as a Period and the hours-and-smaller part as a Duration
• Figure out what you want your Duration to be for non-uniform parts like years and months. (For example, you could add the period to 2000-01-01 and work out the days since then in the result.)
• Add the two Duration results together

But before you write any code, it's worth figuring out your precise requirements. What do you want to do with the result? If you want to add it to a LocalDateTime for example, it would be better to keep the Period and Duration separate.

java.time.Duration.parse() does not support ISO-8601 duration strings that include years (Y) or months (M).

This is because Duration only supports time-based durations, not calendar-based durations. There is ambiguity in calendar-based durations e.g. years or months have different lengths, so it is not precise to use them for durations.

According to the docs, parse method:

Obtains a Duration from a text string such as PnDTnHnMn.nS.

If you want to parse something like "P5Y8M4W3D", you should use java.time.Period. Period represents years, months, days - calendar-based units.

Refer to Javadoc for Class Duration; it says

This class models a quantity or amount of time in terms of seconds and nanoseconds. It can be accessed using other duration-based units, such as minutes and hours. In addition, the DAYS unit can be used and is treated as exactly equal to 24 hours, thus ignoring daylight savings effects. See Period for the date-based equivalent to this class.

This means that PT5M is meant to work, but P5Y8M4W3D needs to be handled by Period instead.

Unfortunately, P10YT10M isn't handled by either of these classes.

PeriodDuration from ThreeTen-Extra

As the other answers say, your strings don’t fit with the Duration class since it is for time-based durations, durations of hours, minutes, seconds and fraction of second. Most of them also don’t fit with the other class for an amount of time, the Period class, which is date-based: for years, months and days. It cannot hold hours, minutes or seconds.

The solution is the PeriodDuration class from the ThreeTen-Extra project. A PeriodDuration combines a Period and a Duration, so holds all of years, months, days, etc., down to nanoseconds. The ThreeTen Extra project was developed alongside java.time and like java.time was inspired from Joda-Time. Just like Period and Duration PeriodDuration parses ISO 8601 format.

import .threeten.extra.PeriodDuration;

public class App  {
    public static void main(String[] args<) {
        String[] input = { "P10YT10M", "P5YT30M", "P5Y8M4W3D" };
        System.out.println("Input      PeriodDuration  Period    Duration");
        for (String i : input) {
            PeriodDuration pd = PeriodDuration.parse(i);
            System.out.format(Locale.ENGLISH, "%-9s  %-14s  %-8s  %s%n",
                    i, pd, pd.getPeriod(), pd.getDuration());
        }
    }
}

Output:

Input      PeriodDuration  Period    Duration
P10YT10M   P10YT10M        P10Y      PT10M
P5YT30M    P5YT30M         P5Y       PT30M
P5Y8M4W3D  P5Y8M31D        P5Y8M31D  PT0S

There’s a lot of things you can do with the PeriodDuration. There’s probably no need to take it apart into a Period and a Duration like I do. I only do it for demonstration. See the documentation link at the bottom for options.

In the last output line we observe that PeriodDuration (just like Period) converts 4 weeks to 28 days and that the absence of any hours or smaller causes the period to be accompanied by a zero-length duration.

Maven dependency:

    <dependency>
      <groupId>.threeten</groupId>
      <artifactId>threeten-extra</artifactId>
      <version>1.8.0</version>
    </dependency>

Links:

• ThreeTen Extra
• PeriodDuration API documentation