How do you subtract Dates in Java? [duplicate]

Question

My heart is bleeding internally after having to go so deep to subtract two dates to calculate the span in number of days:

    GregorianCalendar c1 = new GregorianCalendar();     GregorianCalendar c2 = new GregorianCalendar();     c1.set(2000, 1, 1);     c2.set(2010,1, 1);     long span = c2.getTimeInMillis() - c1.getTimeInMillis();     GregorianCalendar c3 = new GregorianCalendar();     c3.setTimeInMillis(span);     long numberOfMSInADay = 1000*60*60*24;     System.out.println(c3.getTimeInMillis() / numberOfMSInADay); //3653 

where it's only 2 lines of code in .NET, or any modern language you name.

Is this atrocious of java? Or is there a hidden method I should know?

Instead of using GregorianCalendar, is it okay to use Date class in util? If so, should I watch out for subtle things like the year 1970?

Thanks

Answer 1

It's indeed one of the biggest epic failures in the standard Java API. Have a bit of patience, then you'll get your solution in flavor of the new Date and Time API specified by JSR 310 / ThreeTen which is (most likely) going to be included in the upcoming Java 8.

Until then, you can get away with JodaTime.

DateTime dt1 = new DateTime(2000, 1, 1, 0, 0, 0, 0); DateTime dt2 = new DateTime(2010, 1, 1, 0, 0, 0, 0); int days = Days.daysBetween(dt1, dt2).getDays(); 

Its creator, Stephen Colebourne, is by the way the guy behind JSR 310, so it'll look much similar.

Answer 2

You can use the following approach:

SimpleDateFormat formater=new SimpleDateFormat("yyyy-MM-dd");  long d1=formater.parse("2001-1-1").getTime(); long d2=formater.parse("2001-1-2").getTime();  System.out.println(Math.abs((d1-d2)/(1000*60*60*24)));