/*
  File:  LeapYearTester.java

  Purpose:  Indicates whether or not a year - entered by the user - is a
  leap year.  A year is a leap year if either one of the following is true:
     1.  the year is divisible by 4 and not by 100
     2.  the year is divisible by 400

  Demonstrates all things boolean - operators and expressions, variables, 
  assignments, and methods
*/
import javax.swing.JOptionPane;

/**
 * A class thats tests whether a given year is a leap year
 */
public class LeapYearTester 
{
    // instance var
    private int year;	// 4-digit year being tested

    /**
     * Create a LeapYearTester object.
     * @param inputYear the year being tested
     * Precondition: inputYear >= 1583
     */
    public LeapYearTester(int inputYear) {
        year = inputYear;
    }

    /**
     * Is a year a leap year?
     * @return true if year is a leap year, false if not
     */
    public boolean isLeapYear() 
    {
        boolean regularLeap ;   // true if "regular" leap year (every 4 years
                                // except for years ending in 00)
        boolean leap400 ;  	// true if "century" leap year (every 400 years)

        regularLeap = (year % 4 == 0) && !(year % 100 == 0);
        leap400 = (year % 400 == 0);

        return regularLeap || leap400;   // true if either is true
    }

    public static void main(String[] args) 
    {
        String input = JOptionPane.showInputDialog("Enter a year >= 1583");

        int inputYear = Integer.parseInt(input);

        LeapYearTester testYear = new LeapYearTester(inputYear);

        // Is it a leap year?

        if (testYear.isLeapYear()) // calls boolean method
        {
            System.out.println(inputYear + " is a leap year.");
        } 
        else 
        {
            System.out.println(inputYear + " is not a leap year.");
        }
    }
}

/* sample output from 4 runs:

2010 is not a leap year.

2020 is a leap year.

2100 is not a leap year.

2000 is a leap year.

*/