timespan false?

[nimo frey]

I have two date objects - I want to get the timespan between the two dates:

return ((endTime.getTime() - startTime.getTime()) / 60*1000);


but it returns for example: 13000 (even it endures only approx 1 second). So I guess, 13000 means 1,3 sec. Is my formula false?

Should I use something like the examples described here: http://code.hammerpig.com/find-time-difference-dates-java.html:

http://code.hammerpig.com/find-time-difference-dates-java.html

public static double DifferenceInSeconds(Date date1, Date date2)
    {
	return DifferenceInMilliseconds(date1, date2) / 1000.0;
    }
 
    private static double DifferenceInMilliseconds(Date date1, Date date2)
    {
	return Math.abs(GetTimeInMilliseconds(date1) - GetTimeInMilliseconds(date2));
    }
 
    private static long GetTimeInMilliseconds(Date date)
    {
	Calendar cal = Calendar.getInstance();
	cal.setTime(date);
	return cal.getTimeInMillis() + cal.getTimeZone().getOffset(cal.getTimeInMillis());
    }

Why is my formula false?

[Jesper de Jong]

That code from Hammerpig looks horrible and it does strange and unnecessary stuff with timezones.

Your formula looks correct. Are you sure your numbers are correct? What do you see if you print the content of the two Date objects:

DateFormat df = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS");
System.out.println("Start time: " + df.format(startTime));
System.out.println("End time: " + df.format(endTime));

Date.getTime() returns a number measured in milliseconds. If you divide that by 60 * 1000 you get a value in minutes. So 13000 means 13000 minutes.

[Rob Spoor]

Jesper Young wrote:If you divide that by 60 * 1000 you get a value in minutes.

Ah, but Nimo doesn't divide by 60 * 1000.

((endTime.getTime() - startTime.getTime()) / 60*1000)

This will first calculate endTime.getTime() - startTime.getTime(); the difference in milliseconds. This is then divided by 60; the difference in milliminutes. That is then multiplied by 1000. Remember, / and * have the same operator precedence, and are therefore evaluated from left to right.

To calculate the difference in minutes the following are two options:

((endTime.getTime() - startTime.getTime()) / 60 / 1000)

(first divide by 60, then divide by 1000)

((endTime.getTime() - startTime.getTime()) / (60 * 1000))

(really divide by 60 * 1000 by ensuring it is evaluated before the division)

These days you should check out TimeUnit though:

TimeUnit.MILLISECONDS.toMinutes(endTime.getTime() - startTime.getTime())

[nimo frey]

hello jesper,

thanks - yes that was my fault.


hello rob,

thank you!! I did not know the TimeUnit-Class. I will use it for my problem as it works like a charm:-)

thanks!!

[Jesper de Jong]

Ah, my mistake. Thanks Rob, I didn't know the TimeUnit class - learned something today!

[Campbell Ritchie]

I thought TimeUnit is an enum.

[Rob Spoor]

It is.

[Jesper de Jong]

Nitpickers!