java - Difference in time - from before midnight to after midnight without date

Question

I am struggling to calculate time when going after midnight:

String time = "15:00-18:05"; //Calculating OK
    //String time = "22:00-01:05"; //Not calculating properly
    String[] parts = time.split("-");

    SimpleDateFormat format = new SimpleDateFormat("HH:mm");
    Date date1 = null;
    Date date2 = null;
    Date dateMid = null;


    String dateInString = "24:00";
    try {
        dateMid = format.parse(dateInString);
    } catch (ParseException e1) {
        e1.printStackTrace();
    }

    try {
        date1 = format.parse(parts[0]);
        date2 = format.parse(parts[1]);
    } catch (ParseException e) {
        e.printStackTrace();
    }

    long difference = date2.getTime() - date1.getTime();


    if (date2.getTime()<date1.getTime()) //in case beyond midnight calculation
    {
        difference = dateMid.getTime()-difference;
    }



    int minutes = (int) ((difference / (1000*60)) % 60);
    int hours   = (int) ((difference / (1000*60*60)) % 24);

    String tot = String.format("%02d:%02d", hours,minutes);
    System.out.println("dif2: "+tot);

Answer 1

If you don't care about daylight saving changes and you assume the world is ideal (which it isn't), you can just subtract the duration between end and start (treating end as the start and start as the end) from 24 hours:

String time = "22:00-01:05";
String[] parts = time.split("-");

LocalTime start = LocalTime.parse(parts[0]);
LocalTime end = LocalTime.parse(parts[1]);
if (start.isBefore(end)) { // normal case
    System.out.println(Duration.between(start, end));
} else { // 24 - duration between end and start, note how end and start switched places
    System.out.println(Duration.ofHours(24).minus(Duration.between(end, start)));
}