Counting Sundays Problem : Euler Project : Problem 19

Counting Sundays : Problem 19 Euler Project

You are given the following information, but you may prefer to do some research for yourself.

• 1 Jan 1900 was a Monday.
• Thirty days has September,
  April, June and November.
  All the rest have thirty-one,
  Saving February alone,
  Which has twenty-eight, rain or shine.
  And on leap years, twenty-nine.
• A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.

How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

JAVA Code

import java.util.*;
import java.io.*;
public class euler19 {
    public static void main(String[] args) throws IOException {
        int day=1,month=1,year=1900;
        int day1=31,month1=12,year1=2000;
        DaysCalculation date = new DaysCalculation();
        DaysCalculation date1 = new DaysCalculation();
        date.setDate(day,month,year);   
        System.out.println("Number of Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000):"+date.countDays(day1,month1,year1));       
        }
    }
class DaysCalculation {
    public void setDate(int d, int m, int y ){
        day = d;
        month = m;
        year = y;
        sundayCount = 0;
        }
    public int countDays(int day1, int month1, int year1 ){
        boolean small = false;
        int weekDpointer=0;
        if (year == year1)
            if (month == month1)
                if (day < day1)
                    small = true;
                else
                    small = false;       
            else if ( month < month1)
                small = true;
            else
                small = false;           
        else if( year < year1)
            small = true;
        else
            small = false;
        if (small == false) {
            int td,tm,ty;
            td = day;
            day = day1;
            day1 = td;
            tm = month;
            month = month1;
            month1 = tm;
            ty = year;
            year = year1;
            year1=ty;
            }   
        while (year < year1+1) {
            /*if(weekDpointer == 6 && day == 1) {
                System.out.println(day+"/"+month+"/"+year+weekDays[weekDpointer]);
                sundayCount++;
            }*/
            day++;
            weekDpointer++;
            if(weekDpointer >= 7)
                weekDpointer %=7;
            if (checkLeap(year) == true) {
                if (day > ldays[month-1]) {
                    day = 1;
                    month ++;
                    if(weekDpointer == 6 && day == 1 && year != 1900) {
                        System.out.println(day+"/"+month+"/"+year+"~~"+weekDays[weekDpointer]);
                        sundayCount++;
                        System.out.println();
                    }
                    if (month > 12) {
                    month = 1;   
                    year++;
                    }
                }
            }   
            else {
                if (day > mdays[month-1]) {
                    day = 1;
                    month ++;
                    if(weekDpointer == 6 && day == 1 && year != 1900) {
                        System.out.println(day+"/"+month+"/"+year+"~~"+weekDays[weekDpointer]);
                        sundayCount++;
                        System.out.println();
                    }
                    if (month > 12) {
                    month = 1;   
                    year++;
                    }
                }   
            }
        } // end of while   
        return sundayCount;       
        }
    private boolean checkLeap(int year) {
        if(year%400==0)
           leap=true;
        else if (year%100==0)
           leap=false;
        else if (year%4==0)
           leap=true;
        else
           leap=false;
           return leap;
        }    
    private boolean flag;
    private static boolean leap;   
    private int day,month,year;
    private int sundayCount;
    String[] weekDays ={"Mon","Tue","Wed","Thu","Fri","Sat","Sun"};
    int[] mdays={31,28,31,30,31,30,31,31,30,31,30,31};
    int[] ldays={31,29,31,30,31,30,31,31,30,31,30,31};   
    }