Question

i’m trying to solve a seemingly simple problem, but just can’t quite get my mind around it.

i have two times startTime and stopTime, which can be considered to be in the format: hh:mm:ss [24hr format].

Now given a third time – timeToTest – i need to find out if timeToTest lies between startTime and stopTime. There is no date information involved, other than just the times.

So for example – if i have startTime = '22:30:00' and stopTime = '03:30:00', then for timeToTest = '01:14:23', the test should return true.

I’ve tried a solution with java.util.Date by converting the times to milliseconds using getTime(), but with any interval which rolls over the 24 hr barrier, the logic fails.

I’m trying to build a solution using Java – but i believe the logic is language independent.

Answer 1

So the simplest solution i could come up with, sticking to plain old java.util.Date, is shown below:

    String d1 = "21:00:00";
    String d2 = "04:00:00";
    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
    String dToTest = "16:00:00";
    boolean isSplit = false, isWithin = false;

    Date dt1 = null, dt2 = null,  dt3 = null;

    dt1 = sdf.parse(d1);
    dt2 = sdf.parse(d2);
    dt3 = sdf.parse(dToTest);

    isSplit = (dt2.compareTo(dt1) < 0);
    System.out.println("[split]: " +isSplit);

    if (isSplit)
    {
        isWithin = (dt3.after(dt1) || dt3.before(dt2));
    }
    else
    {
        isWithin = (dt3.after(dt1) && dt3.before(dt2));
    }

    System.out.println("Is time within interval? " +isWithin);

feel free to point out any mistakes – would love to work and fix it.