Java finding difference between times

问题:

i have some problem while finding difference between times, if i try to find difference in todays time (say t1 = "08:00:00" and t2 = "10:00:00" then it is giving correct output,)but when i try to find the difference like t1 = "20:00:00"(which is todays time) and t2 ="08:00:00"(which is next day morning),i want the output as 12 hours but i a getting wrong outputs. kindly help me.

    String t1 = "20:00:00"; 
    String t2 = "12:00:00";
    String t3 = "24:00:00";
    SimpleDateFormat sDf = new SimpleDateFormat("HH:mm:ss");
    Date d1 = sDf.parse(t1);
    Date d2 = sDf.parse(t2);
    Date d3 = sDf.parse(t3);
    long s1,s2,s3,s4,dif1,dif2,dif3,minutes,hrs;
    dif1 = d2.getTime() - d1.getTime();
    s1 = dif1/1000;
    System.out.println("s1 "+s1);
    if(s1<0){
        dif2 = d3.getTime() - d1.getTime();
        s2 = dif2/1000;
        System.out.println("s2 "+s2);
        dif3 = d2.getTime();
        s3 = dif3/1000;
        System.out.println("s3 "+s3);
        s4 = s2+s3;
        minutes = s4 / 60;
        s4 = s4 % 60;
        hrs = minutes / 60;
        minutes = minutes % 60;
        System.out.println("time difference is : "+hrs+": "+minutes+" :"+s4);
    }else{
        minutes = s1 / 60;
        s1 = s1 % 60;
        hrs = minutes / 60;
        minutes = minutes % 60;
        System.out.println("time difference is : "+hrs+": "+minutes+" :"+s1);
    }

回答1:

Any date/time manipulation/calculation should be done though the use of well defined and tested APIs like Java 8's Time API or Joda Time

Java 8

public class TestTime {

    public static void main(String[] args) {
        // Because of the ability for the time to roll over to the next
        // day, we need the date component to make sense of it, for example
        // 24:00 is actually 00:00 of the next day ... joy
        LocalDateTime t1 = LocalTime.of(20, 00).atDate(LocalDate.now());
        LocalDateTime t2 = LocalTime.of(12, 00).atDate(LocalDate.now());
        LocalDateTime t3 = LocalTime.MIDNIGHT.atDate(LocalDate.now()).plusDays(1);

        if (t1.isAfter(t2)) {
            System.out.println("Before");
            Duration duration = Duration.between(t2, t3);
            System.out.println(format(duration));
        } else {
            System.out.println("After");
            Duration duration = Duration.between(t2, t1);
            System.out.println(format(duration));
        }
    }

    public static String format(Duration duration) {
        long hours = duration.toHours();
        duration = duration.minusHours(hours);

        return String.format("%02d hours %02d minutes", hours, duration.toMinutes());
    }

}

Which outputs

12 hours 00 minutes

The question I can't seem to answer in your code is why you did this s4 = s2+s3;, basically adding 12:00 to 24:00

回答2:

See some options here

such as :

     LocalDate today = LocalDate.now()
     LocalDate yeasterday = today.minusDays(1);
     Duration oneDay = Duration.between(today, yesterday);
     Duration.between(today.atTime(0, 0), yesterday.atTime(0, 0)).toDays()   // another option

回答3:

String time1 = "08:00:00";
String time2 = "17:00:00";

SimpleDateFormat format = new SimpleDateFormat("HH:mm:ss");
Date date1 = format.parse(time1);
Date date2 = format.parse(time2);
long difference = date2.getTime() - date1.getTime(); 

回答4:

Not using Java 8 or Joda-Time, and ensuring that local time zone DST is not involved.

public static void printDiff(String time1, String time2) throws ParseException {
    SimpleDateFormat df = new SimpleDateFormat("HH:mm:ss");
    df.setTimeZone(TimeZone.getTimeZone("UTC"));
    int seconds = (int)(df.parse(time2).getTime() - df.parse(time1).getTime()) / 1000;
    if (seconds < 0)
        seconds += 24 * 60 * 60;
    int minutes = seconds / 60;
    int hours = minutes / 60;
    seconds %= 60;
    minutes %= 60;
    System.out.printf("There are %d hours %d minutes %d seconds from %s to %s%n",
                      hours, minutes, seconds, time1, time2);
}

Test

public static void main(String[] args) throws Exception {
    printDiff("08:00:00", "10:00:00");
    printDiff("20:00:00", "08:00:00");
    printDiff("15:47:22", "11:12:38");
    printDiff("08:00:00", "07:59:59");
    printDiff("08:00:00", "08:00:00");
}

Output

There are 2 hours 0 minutes 0 seconds from 08:00:00 to 10:00:00
There are 12 hours 0 minutes 0 seconds from 20:00:00 to 08:00:00
There are 19 hours 25 minutes 16 seconds from 15:47:22 to 11:12:38
There are 23 hours 59 minutes 59 seconds from 08:00:00 to 07:59:59
There are 0 hours 0 minutes 0 seconds from 08:00:00 to 08:00:00