/*
    Method3.java
    CIS 160
    10/18/04

    user-defined methods returning values
*/

import java.io.*;

public class Method3 {
    private static BufferedReader kbd = new BufferedReader(
        new InputStreamReader(System.in));

    public static void main(String[] args) throws IOException {
        int year;
        boolean more = true;
        do {
            System.out.println("This program determines whether a given year is a leap year");
            year = getYear();
            if (isLeap(year)) {
                System.out.println(year + " is a leap year.");
            } else {
                System.out.println(year + " is not a leap year.");
            }
            System.out.println();
            more = moreData();
        } while (more);
    }

    private static int getYear() throws IOException {
        int y = 0;
        boolean valid = false;
        do {
            System.out.print("Enter a year: ");
            String s = kbd.readLine();
            try {
                y = Integer.parseInt(s);
                valid = true;
            } catch (NumberFormatException e) {
                System.out.println("Invalid year entry. Try again!");
            }
        } while (!valid);
        return y;
    }

    private static boolean isLeap(int y) {
        boolean leap = false;
        if (y % 4 == 0) leap = true;
        if (y % 100 == 0) leap = false;
        if (y % 400 == 0) leap = true;
        return leap;
    }

    private static boolean moreData() throws IOException {
        boolean go_on = false;
        char c;
        do {
            System.out.print("Do you want to enter more data? y/n: ");
            c = kbd.readLine().toUpperCase().charAt(0);
            if (c == 'Y') go_on = true;
            else if (c != 'N') System.out.println("Invalid response. Try again!");
        } while (c != 'Y' && c != 'N');
        return go_on;
    }
}