How to correct calculate the running time

Question

I want to calculate the total running time of my program from start to end and refresh running time in JFrame, but when I run my program I get excess 70 years, 1 day and 2 hours. Why ? What wrong ?

private void setMachineTime(){
    Timer timer = new Timer();
    long startTime = new Date().getTime();
    timer.scheduleAtFixedRate(new TimerTask() {
       @Override
       public void run() {
           long endTime = new Date().getTime();
           long diffTime = endTime - startTime ;
           String time = new SimpleDateFormat("yy:mm:dd:HH:mm:ss").format(diffTime);
           System.out.println(time);
       }
    }, 0, 1000);
}

actual result

UPD: I rewrote code with my own format time method. Now I got what I want. Thanks to all of you.

private void setMachineTime(){
    Timer timer = new Timer();
    long startTime = new Date().getTime();
    timer.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {

            long endTime = new Date().getTime();
            long diffTime = endTime - startTime;
            String diffSeconds = formatTime(diffTime / 1000 % 60);
            String diffMinutes = formatTime(diffTime / (60 * 1000) % 60);
            String diffHours = formatTime(diffTime / (60 * 60 * 1000) % 24);
            System.out.println(diffHours + ":" + diffMinutes + ":" + diffSeconds);
        }
    }, 0, 1000);
}

private String formatTime(long diff){
    long t;
    t = diff;
    if(t < 10){
        return String.valueOf("0"+t);
    } else {
        return String.valueOf(t);
    }
}

You're not getting 70 years. You're making a string based on a date that is interpreted as the amount of time since 12:00 AM 1 January 1970. Then you're printing the year, which is 1970, or '70'. See what happens if you try `String time = new SimpleDateFormat("yy:mm:dd:HH:mm:ss").format(0);` - it will say that it's that exact date. Also check out http://stackoverflow.com/questions/17940200/how-to-find-the-duration-of-difference-between-two-dates-in-java — childofsoong, May 16 '16 at 18:40
Actually, now that I think about it, it's probably not going to say that exact date, but instead adjust for your time zone. Same general principle, though. — childofsoong, May 16 '16 at 18:41
[How to format an elapsed time interval in hh:mm:ss.SSS format in Java?](http://stackoverflow.com/questions/6710094/how-to-format-an-elapsed-time-interval-in-hhmmss-sss-format-in-java) — shmosel, May 16 '16 at 19:36

amal · Answer 1 · 2016-05-16T19:31:35.547

You are formatting the time difference as yy:mm:dd:HH:mm:ss. Just printing out diffTime would give you the milliseconds, divide by 1000 if you need seconds.

EDIT: I think i see what you are trying to do, but you are dealing with a time interval, which cannot be formatted as a date. You'll need to roll your own formatting for displaying the time as seconds, minutes, hours etc. or use an external library.

score 0 · Answer 2 · answered May 16 '16 at 18:43

getTime return number of milliseconds from 1.1.1970...and same is for SimpleDateFormat converting number to date (and then formating it). It means when your diffTime = 0, SimpleDateFormat will try to format Date 1.1.1970 0:00:00 and with your formating string it will be 70:01:01:00:00:00. Try to use http://joda-time.sourceforge.net/api-release/org/joda/time/Interval.html instead.

And by the way, your formating string is wrong anyway...you use mm where I supouse you wanted month...but mm are minutes.

How to correct calculate the running time

2 Answers2