A leap year is exactly divisible by 4 except for century years (years ending with 00). The century year is a leap year only if it is perfectly divisible by 400.

Example: Java Program to Check a Leap Year

1. public class LeapYear {
3. public static void main(String[] args) {
5. int year = 1900;
6. boolean leap = false;
8. if(year % 4 == 0)
9. {
10. if( year % 100 == 0)
11. {
12. // year is divisible by 400, hence the year is a leap year
13. if ( year % 400 == 0)
14. leap = true;
15. else
16. leap = false;
17. }
18. else
19. leap = true;
20. }
21. else
22. leap = false;
24. if(leap)
25. System.out.println(year + " is a leap year.");
26. else
27. System.out.println(year + " is not a leap year.");
28. }
29. }

When you run the program, the output will be:

1900 is not a leap year.

When you change the value of year to 2012, the output will be:

2012 is a leap year.

In the above program, given year 1900 is stored in the variable year.

Since 1900 is divisble by 4 and is also a century year (ending with 00), it has be divisble by 400 for a leap year. Since it’s not divisible by 400, 1900 is not a leap year.

But, if we change year to 2000, it is divisible by 4, is a century year and is also divisible by 400. So, 2000 is a leap year.

Likewise, If we change year to 2012, it is divisible by 4 and is not a century year, so 2012 a leap year. We don’t need to check if 2012 is divisible by 400 or not.