Calculate the amount of seconds between start and end in Java?

I'm trying to solve a task that I have to do that is to calculate the amount of seconds between a star time and a end time like a race. In the format hhmmss. With the amount of seconds finally calculate the result in hours minutes and seconds. This is a beginners course with non-objective programming, 开发者_运维问答so the code I use must be simple and without any extra classes to handle time. The reason why I ask is because my calculation sometimes calculate a wrong result. I have done it like this:

totalAmountOfSecondsPerHour = (endHour - startHour) * 3600;
totalAmountOfMinutesPerMinutes = Math.abs((endMinutes - startMinutes) * 60);
totalAmountOfSeconds = Math.abs(endSeconds - startSeconds));

I use Math.abs to get rid of negative numbers.

To get the total amount in seconds I add all variables. Finally to get the result time in hhmmss I do like this:

resultHour = totalAmountOfSeconds / 3600;
rest totalAmountOfSeconds % 3600;

resultMinutes = rest / 60;
resultSeconds = rest % 60;

When I enter a starting time like 150030 and end time like 165015 the result is 1 hour 50 minutes an 15 seconds. I guess i should be more correct if it was 45 seconds!? What could be wrong in my calculation? Is there a better way or could I modify or simplify my code the make a correct result? Preciate some help! Thanks!

It's because you use the Math.abs()

let give you a small example: The app start at 00:00:59 and finish 2 seconds later so at 00:01:01

totalAmouneOfMinutesPerMinutes = Math.abs(1 - 0) * 60  = 60
totalAmountOfSeconds = Math.abs(1 - 59) = 58   

so 60 + 58 = 118 seconds instead of 2. If we remove the Math.abs, we'll have:

totalAmouneOfMinutesPerMinutes = (1 - 0) * 60  = 60
totalAmountOfSeconds = (1 - 59) = -58   

60 + (-58) = 2 seconds (like it's suppose).

For your seconds calc you are essentially doing

15 - 30 = -15 ABS(-15) = 15

So there's your problem.

You may want to try IF the seconds are negative THEN add 60.

Take the example of start time: 1:10:10 and end time 1:11:05 obviously the difference should be 55 seconds.

But you do abs(5-10) for the seconds and get 5 seconds. And you get 1 minute 5 seconds.

You have two approaches to fix this: Get rid of the abs and instead if you get a negative result add that (negative) amount to the amount of the next 'higher' value.

So in the example instead of adding abs(-5) to 1 minute you add -5 to 1 minute, resulting in 0 minutes and 55 seconds.

While this will work it will get quite confusing.

A better approach would be: convert start and end time into seconds. Take the difference. Convert the result back into hours, minutes and seconds

Those Math.abs tripped you up... Convert the time to seconds, do substraction and then convert back to hhmmss format.