[java] How to format a duration in java? (e.g format H:MM:SS)

This is a working option.

public static String showDuration(LocalTime otherTime){          
    DateTimeFormatter df = DateTimeFormatter.ISO_LOCAL_TIME;
    LocalTime now = LocalTime.now();
    System.out.println("now: " + now);
    System.out.println("otherTime: " + otherTime);
    System.out.println("otherTime: " + otherTime.format(df));

    Duration span = Duration.between(otherTime, now);
    LocalTime fTime = LocalTime.ofNanoOfDay(span.toNanos());
    String output = fTime.format(df);

    System.out.println(output);
    return output;
}

Call the method with

System.out.println(showDuration(LocalTime.of(9, 30, 0, 0)));

Produces something like:

otherTime: 09:30
otherTime: 09:30:00
11:31:27.463
11:31:27.463