javaleap-yearacm-java-libraries

Java Code for calculating Leap Year


I am following "The Art and Science of Java" book and it shows how to calculate a leap year. The book uses ACM Java Task Force's library.

Here is the code the books uses:

import acm.program.*;

public class LeapYear extends ConsoleProgram {
    public void run()
    {

        println("This program calculates leap year.");
        int year = readInt("Enter the year: ");     

        boolean isLeapYear = ((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0));

        if (isLeapYear)
        {
            println(year + " is a leap year.");
        } else
            println(year + " is not a leap year.");
    }

}

Now, this is how I calculated the leap year.

import acm.program.*;

public class LeapYear extends ConsoleProgram {
    public void run()
    {

        println("This program calculates leap year.");
        int year = readInt("Enter the year: ");

        if ((year % 4 == 0) && year % 100 != 0)
        {
            println(year + " is a leap year.");
        }
        else if ((year % 4 == 0) && (year % 100 == 0) && (year % 400 == 0))
        {
            println(year + " is a leap year.");
        }
        else
        {
            println(year + " is not a leap year.");
        }
    }
}

Is there anything wrong with my code or should i use the one provided by the book ?

EDIT :: Both of the above code works fine, What i want to ask is which code is the best way to calculate the leap year.


Solution

  • The correct implementation is:

    public static boolean isLeapYear(int year) {
      Calendar cal = Calendar.getInstance();
      cal.set(Calendar.YEAR, year);
      return cal.getActualMaximum(Calendar.DAY_OF_YEAR) > 365;
    }
    

    But if you are going to reinvent this wheel then:

    public static boolean isLeapYear(int year) {
      if (year % 4 != 0) {
        return false;
      } else if (year % 400 == 0) {
        return true;
      } else if (year % 100 == 0) {
        return false;
      } else {
        return true;
      }
    }