- Recall: Leap year description (Wikipedia):
- In the Gregorian calendar, the current standard calendar
in most of the world, most years that
are evenly divisible by 4 are leap years.
- Years that are evenly divisible by 100 are not leap years, unless they are also evenly divisible by 400, in which case they are leap years
- In the Gregorian calendar, the current standard calendar
in most of the world, most years that
are evenly divisible by 4 are leap years.
- Constructing a Boolean expression for "leap year":
- (most) years that
are evenly divisible by 4 are leap years:
Year is leap year if: year % 4 == 0 (divisible by 4) - Years that are evenly divisible by 100
are not leap years:
Years that are evenly divisible by 100 ==> (year % 100 == 0) They are NOT leap years !!! So: a year is leap if: divisible by 4 AND not divisible by 100 Conclusion (so far): (year % 4 == 0) && !(year % 100 == 0) - Continued: unless
they are
also evenly divisible by 400,
in which case they are leap years
Meaning: a year is divisible by 400 is ALWAYS leap So a year is leap year if: (whatever makes it leap) OR (divisible by 400) Result: ( (year % 4 == 0) && !(year % 100 == 0) ) || (year % 400 == 0)
BTW, because && has a higher priority than ||, we do not need the brackets:
(year % 4 == 0) && !(year % 100 == 0) || (year % 400 == 0)
- (most) years that
are evenly divisible by 4 are leap years:
- Java program:
import java.util.Scanner; public class LeapYear02 { public static void main(String[] args) { int year; boolean leap; Scanner in = new Scanner(System.in); // Construct Scanner object System.out.print("Enter year:"); year = in.nextInt(); // Read in year if ( (year % 4 == 0) && !(year % 100 == 0) || (year % 400 == 0) ) { System.out.println("It is a leap year"); } else { System.out.println("It is NOT a leap year"); } } }
- Example Program:
(Demo above code)
- Prog file: click here
How to run the program:
- Right click on link and
save in a scratch directory
- To compile: javac LeapYear02.java
- To run: java LeapYear02