Android Java : How to subtract two times?

Question

I use some kind of stopwatch in my project and I have

start time ex: 18:40:10 h
stop time  ex: 19:05:15 h

I need a result from those two

Answer 1

If you have strings you need to parse them into a java.util.Date using java.text.SimpleDateFormat. Something like:

        java.text.DateFormat df = new java.text.SimpleDateFormat("hh:mm:ss");
        java.util.Date date1 = df.parse("18:40:10");
        java.util.Date date2 = df.parse("19:05:15");
        long diff = date2.getTime() - date1.getTime();

Here diff is the number of milliseconds elapsed between 18:40:10 and 19:05:15.

EDIT 1:

Found a method online for this (at http://www.javaworld.com/javaworld/jw-03-2001/jw-0330-time.html?page=2):

  int timeInSeconds = diff / 1000;
  int hours, minutes, seconds;
  hours = timeInSeconds / 3600;
  timeInSeconds = timeInSeconds - (hours * 3600);
  minutes = timeInSeconds / 60;
  timeInSeconds = timeInSeconds - (minutes * 60);
  seconds = timeInSeconds;

EDIT 2:

If you want it as a string (this is a sloppy way, but it works):

String diffTime = (hours<10 ? "0" + hours : hours) + ":" + (minutes < 10 ? "0" + minutes : minutes) + ":" + (seconds < 10 ? "0" + seconds : seconds) + " h";

EDIT 3:

If you want the milliseconds just do this

long timeMS = diff % 1000;

You can then divide that by 1000 to get the fractional part of your seconds.