// LeapYear.java - Tells whether a give year is leap year or not.
// Michael Maus, 22 Sept 2004

import javax.swing.*;

public class LeapYear {
    
    //===================================================================== main
    public static void main(String[] args) {
        //... Variables
        String yearStr;    // String version of year before conversion to int.
        int    year;       // year
        String leapResult; // Tell's whether it's a leap year or not.
        
        //... Input
        yearStr = JOptionPane.showInputDialog(null, "Enter a year.");
        year = Integer.parseInt(yearStr);
        
        //... Computation and output
        if (isLeapYear(year)) {
            leapResult = " is a leap year";
        } else {
            leapResult = year + " isn't a leap year";
        }
        
        //... Output
        JOptionPane.showMessageDialog(null, leapResult);
        
        System.exit(0);  // Stop GUI program
    }
    
    //=============================================================== isLeapYear
    static boolean isLeapYear(int yr) {
        return (yr%400 == 0) || ((yr%4 == 0) && (yr%100 != 0));
    }
}