Store numerical value in form of HH:MM (Not time)

Question

I need to figure out how to store times like 12:45, 13:45 etc.. so in format of HH:MM It is NOT NECESSARY to use date functionality in java, these will not be used to time an event or anything of that matter, all I need them for is to perform operations like 13:45 - 12:45 and get output which in this case is 01:00 I tried doing this with doubles, however ran into issue of something like 13.45 + 00.35 = 13.80; as there are only 60 minutes in a hour, expected output should be 14.20

I'm trying to figure out how to do this with date as well, but remember at the moment I do not need to be concerned about things like time zones, calendar dates etc.. I need to figure out how to make numbers behave like hours and minutes.

Sorry if this is confusing.

If you want numbers to behave like times, treat them as such. Then you won't have to bother with wrapping around 60 and stuff like that. — Jeroen Vannevel, Nov 02 '13 at 13:40
@JeroenVannevel That's totally what I just wrote, but you were faster ;-) — L.Butz, Nov 02 '13 at 13:43
@JeroenVannevel could you expand on your comment, as now even if I treat a double like 12.30 as a time adding lets say 45 minutes, so 00.45 to it will result in 12.75, and that is not time at all, I probably don't get the idea just yet. — Ilja, Nov 02 '13 at 13:48
@ilya: just create two dates and use those objects (`Calendar`). You don't care about the date aspect, just the time. — Jeroen Vannevel, Nov 02 '13 at 14:00
"there are only 60 minutes in a hour" = The reason you should time data as time rather than as decimal numbers. [Joda-Time](http://www.joda.org/joda-time/) provides the time-based objects you need. — Basil Bourque, Nov 03 '13 at 07:23

score 1 · Answer 1 · answered Nov 02 '13 at 13:57

You should create an object. Call it HHMM. It would look something like this

public class HHMM {

  private int HH;
  private int MM;

  public HHMM(HH, MM) {

    this.HH = HH
    this.MM = MM

  }

  public toStr() {
    return HH + ":" + MM
  }

  public minus(HHMM hhmm){
    //write code here that subtracts the passed HHMM from this HHMM
  }

  //make a plus method too, and any other methods, etc.


}

score 1 · Accepted Answer · answered Nov 02 '13 at 14:05

Alright, here's my comment written out:

Calendar end = new GregorianCalendar(2013, 05, 05, 12, 40, 0);
Calendar start = new GregorianCalendar(2013, 05, 05, 12, 15, 0);

Calendar diff = end - start;
int minutes = diff.get(Calendar.Minutes);
int seconds = diff.get(Calendar.Seconds);

You don't have to use the date part to use the time part.

matsev · Answer 3 · 2013-11-02T14:41:08.420

1

Joda-Time has already implemented what you are looking for in the LocalTime class:

LocalTime start = LocalTime.parse("12:45");
LocalTime end = LocalTime.parse("13:45");
Period period = new Period(start, end);

and

LocalTime start = new LocalTime(13, 45);
LocalTime later = start.plusMinutes(35);

edited Nov 02 '13 at 14:41

answered Nov 02 '13 at 14:16

matsev

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Correct answer by matsev. With a Period object in hand, you can calculate elapsed time. See [How to calculate elapsed time from now with Joda Time?](http://stackoverflow.com/questions/2179644/how-to-calculate-elapsed-time-from-now-with-joda-time). – Basil Bourque Nov 03 '13 at 07:29

initramfs · Answer 4 · 2013-11-02T14:01:25.500

Store all numbers in minutes then. Using a single integer, you can do simple time manipulation by doing integer math. Mod all your operations by 1440 (60*24) if you don't care about what day it is:

Example:

int time = 600;

//Example time operation
time = (5000 + time) % 1440; //Day-insensitve

//Perform this check if you suspect time will become negative.
if(time < 0){
    time = 1440 + time;
}

//Display time
int hours = time / 60; //Integer division of 60, get the maximum number of "perfect 60s" in your time component.
int minutes = time % 60; //Integer mod, get the remainder since the last "perfect 60"

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

Note how most time keeping constructs simply store time/date or whatever as a single numerical value with a base unit. Take for example: System.currentTimeMillis() which returns time as a number of milliseconds since the epoch.

If you require only simple manipulation operations with something like time, you need only understand how to parse a single value into your desired components (e.g seconds, minutes, hours). Operations on this numerical value is same like traditional mathematics.

score 0 · Answer 5 · edited Nov 03 '13 at 07:33

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One way I use to make transactions with date and hours in java, I use a framework, called Joda-Time, he is very good. Only you just download the. Jar, and looks at the ways how to do operations with més, years and days. Using this framework vc saves a lot of headaches by doing more complex codes.

edited Nov 03 '13 at 07:33

Basil Bourque

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answered Nov 02 '13 at 14:00

Johnatan Dantas

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Store numerical value in form of HH:MM (Not time)

5 Answers5