Check if one date is exactly 24 hours or more after another

Question

I am using the compareTo method in Java to try and check if a certain date is greater than or equal than 24 hours after another date.

How do I determine what integer to compare the date to?

Answer 1

Use the Calendar class. If you already have a Date object, you can still use Calendar:

Date aDate = . . .
Calendar today = Calendar.getInstance();
today.setTime(aDate);
Calendar tomorrow = Calendar.getInstance();
tomorrow.setTime(aDate);
tomorrow.add(Calendar.DAY, 1);
Date tomorrowDate = tomorrow.getTime(); // if you need a Date object

Answer 2

Answer depends on what you want to achieve.

One way, could be checking difference in milliseconds. 24 h in milliseconds can be calculated via

24  *  60  *  60  *  1000   =  86400000
h      min    sec    millis  

(in code you can also write TimeUnit.HOURS.toMillis(24) which IMO is more readable)

So now you can just check if difference between two dates (expressed in milliseconds) is greater than 86400000.