Creation and usage of a class

[Robert Richard]

I created a class that does various things with given dates. In that class I attempted to write a method the will calculate the month/day/year of the next day. What I have isn't working(keep getting an error message). If someone could take a look and tell me why it wont work and/or point me in the right direction, that would be awesome.

Date Class:

public class Date {
	public int day;
	public int month;
	public int year;
	Date(int m, int d, int y){
		day=d;
		month=m;
		year=y;
	}
	public String toString(){
		String dates=(month+"/"+day+"/"+year);
		return dates;
	}
	public boolean equals(Date date2){
		return day==date2.day&&month==date2.month&&year==date2.year;
		}
	public static boolean isLeapYear(int y){
		return y%400==0&&y%100==0&&y%4==0;
	}
	public static int daysInMonth(int m, int y) {
		final int monthDays[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
		if (m == 2 && isLeapYear(y))
			return 29;
		return monthDays[m];
	}
	public static Date nextDay(){
		int m=4;
		int d=30;
		int y=2012;
		if(d<=daysInMonth(m,y)){
			d=d+1;
			m=m+0;
			y=y+0;
			return nextDay();
		}else
			if(d>daysInMonth(m,y)){
				m=m+1;
				d=1;
				y=y+0;
				return nextDay();
			}else
				if(m>12)
					d=1;
					m=1;
					y=y+1;
				return nextDay();
	}
}

Date Tester:

public class DateTester {

	public static void main(String[] args) {
		Date today=new Date(04,24,2012);
		Date myBDay=new Date(01,05,2012);
		Date myBrosBDay=new Date(07,20,2012);
		Date xMas=new Date(12,25,2012);
		Date today2 = new Date(04,24,2012);
		System.out.println("Today's date is " +today);
		System.out.println("My birthday is "+myBDay);
		System.out.println("My brother's birthday is "+myBrosBDay);
		System.out.println("Christmas is on "+xMas);
		System.out.println(today + " equals " + today2 + " " + today.equals(today2) );
		System.out.println(today + " equals " + xMas + " " + today.equals(xMas) );
		System.out.println("Is 2000 a leap year? " +Date.isLeapYear(2000));
		System.out.println("Is 2001 a leap year? " +Date.isLeapYear(2001));
		System.out.println("Is 1600 a leap year? " +Date.isLeapYear(1600));
		System.out.println("Is 2012 a leap year? " +Date.isLeapYear(2012));
		System.out.println("Tomorrow is "+Date.nextDay());
	}

}

Output:
Today's date is 4/24/2012
My birthday is 1/5/2012
My brother's birthday is 7/20/2012
Christmas is on 12/25/2012
4/24/2012 equals 4/24/2012 true
4/24/2012 equals 12/25/2012 false
Is 2000 a leap year? true
Is 2001 a leap year? false
Is 1600 a leap year? true
Is 2012 a leap year? false
Exception in thread "main" java.lang.StackOverflowError
at Date.daysInMonth(Date.java:22)
at Date.nextDay(Date.java:31)<--This keeps repeating for quite a few more lines

Again if someone could help me out that would awesome! In the mean time I'll keep at it.

[Mohamed Sanaulla]

In your nextDay method you are recursively calling it- see return nextDay(). But I think your requirements is to return a new Date object. You have the date, month and year values calculated, instead of invoking nextDay() again you need to actually return a new Date object.

[Winston Gutkowski]

Robert Richard wrote:Again if someone could help me out that would awesome! In the mean time I'll keep at it.

Mohamed's basically done that, but a little tip for you:
If you use 1-based months, don't use arrays - or if you do, document why, for example, your array of day lengths has a '0' as its first element (you and I both know why, but it's a non-standard use of an array).

My slight preference would be to keep both months and days 0-based internally - you'll find it makes calculations a lot easier - although there's nothing to stop you accepting 1-based values in your constructor.
If you really feel you must use 1-based values everywhere, what about something like:

public static int daysInMonth(int m, int y) {
   switch(m) {
      case 2:
         return isLeapYear(y) ? 29 : 28;
      case 4:
      case 6:
      case 9:
      case 11:
         return 30;
      default:
         return 31;
   }
}

? Very clear, and no arrays needed.

HIH

Winston