I have a problem with a task, I need to add a method to a class that returns the name of the day of the week for a given date. You have to do it in two ways, using the methods of shifting by a week (comparing to the selected reference date, e.g. May 14, 2023 is Sunday) and by determining using the modulo operation (https://en.wikipedia.org/w/index.php?title=Zeller%27s_congruence&oldid=1033222037.
my code shows wrong results using both methods, i don't understand why. e.g. when given 3/17/2030, the reference method displays Wednesday, and the Zeller algorithm displays Friday, when the correct result is Sunday. please help me find the error. I don't want to use any built-in classes or functions
import java.util.Scanner;
import java.util.Comparator;
class DateComparator implements Comparator<Date>{
@Override
public int compare(Date date1, Date date2){
int yearComparison = Integer.compare(date1.getYear(), date2.getYear());
if( yearComparison != 0){
return yearComparison;
}
int monthComparison = Integer.compare(date1.getMonth(), date2.getMonth());
if(monthComparison != 0){
return monthComparison;
}
return Integer.compare(date1.getDay(), date2.getDay());
}
}
class Month{
private int monthNumber;
private String name;
private int days;
public Month(int monthNumber, String name, int days){
this.monthNumber = monthNumber;
this.name = name;
this.days = days;
}
public int getMonthNumber() {
return monthNumber;
}
public int getDays() {
return days;
}
public void setDays(int days){
this.days = days;
}
}
public class Date {
Months monthsObj = new Months();
private int year;
private int month;
private int day;
public Date() {
}
public Date(int year, int month, int day){
this.year = year;
this.month = month;
this.day = day;
}
public int getYear(){
return year;
}
public void setYear(int year){
this.year = year;
}
public int getMonth(){
return month;
}
public void setMonth(int month){
this.month = month;
}
public int getDay(){
return day;
}
public void setDay(int day){
this.day = day;
}
public void printDate(){
System.out.println(year + "-" + month + "-" + day);
}
public void incrementWeek(){
int daysInMonth = monthsObj.getDaysInMonth(year, month);
day += 7;
if(day > daysInMonth){
day -= daysInMonth;
month++;
if(month > 12){
year++;
month = 1;
}
}
}
public void decrementWeek(){
int daysInPreviousMonth;
int daysToRemove = 8 - day;
if(daysToRemove <= 0){
day -= 7;
}else{
month--;
if(month == 0){
month = 12;
year--;
}
daysInPreviousMonth = monthsObj.getDaysInMonth(year, month);
day = daysInPreviousMonth + 1 - daysToRemove;
}
}
public void whatDay() {
int h = (day + 13 * (month + 1) / 5 + year % 100 + (year % 100) / 4 + (year / 100) / 4 - 2 * (year / 100)) % 7;
String[] days = { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
System.out.println(days[h]);
}
public void moveWeek(Date reference, Date calendar, int result){
String[] days = { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};
if(result > 0){
while((reference.getYear() != calendar.getYear()) || (reference.getMonth() != calendar.getMonth()) || (reference.getDay()-calendar.getDay() >= 7)){
calendar.incrementWeek();
calendar.printDate();
}
}
if(result < 0){
while((reference.getYear() != calendar.getYear()) || (reference.getMonth() != calendar.getMonth()) || ((reference.getDay()-calendar.getDay() >= 7)||(reference.getDay()- calendar.getDay()<0))){
calendar.decrementWeek();
calendar.printDate();
}
}
int difference = reference.getDay() - calendar.getDay();
System.out.println(days[6-difference]);
}
public static void main(String[] args) {
DateComparator comparator = new DateComparator();
Scanner sc = new Scanner(System.in);
System.out.println("podaj dzien, miesiac i rok:");
int day = sc.nextInt();
int month = sc.nextInt();
int year = sc.nextInt();
Date reference = new Date(2023, 5, 14);
Date calendar = new Date(year, month, day);
calendar.moveWeek(reference, calendar, comparator.compare(reference, calendar));
calendar.whatDay();
}
}
class Months{
private static final Month[] months = {
new Month(1, "January", 31),
new Month(2, "February", 28),
new Month(3, "March", 31),
new Month(4, "April", 30),
new Month(5, "May", 31),
new Month(6, "June", 30),
new Month(7, "July", 31),
new Month(8, "August", 31),
new Month(9, "September", 30),
new Month(10, "October", 31),
new Month(11, "November", 30),
new Month(12, "December", 31)
};
public boolean isLeapYear(int year){
return (year % 4 == 0 && year % 100 !=0) || year % 400 == 0;
}
public int getDaysInMonth(int year, int month){
if(isLeapYear(year) && month == 2){
months[1].setDays(29);
}
return months[month-1].getDays();
}
}
