datemain.java

A java program asking the user to enter a date, the program will calculate the julian date, and take

import java.util.Scanner ;

class Date {

   private long year  = 0 ;
	private long month = 0 ;
	private long days  = 0 ; 
	private long julianDate ;
	
   Date() {
	   year       = askForInt("Enter year: "); 
		month      = askForInt("Enter month: ") ;
		days       = askForInt("Enter day: ") ;
		julianDate = returnJulianDate(year, month, days) ;
	}	

   public static int askForInt(String message) {
	Scanner keyboard ;
	int aValue ;
	
	   keyboard = new Scanner(System.in) ;
		System.out.print(message) ;
		aValue = keyboard.nextInt() ;
		return aValue ;
	}
	
	public long getYear() {
	   return year ;
	}
	
	public long getMonth() {
	   return month ;
	}
	
	public long getDays() {
	   return days ;
	}
	
	public void setYear(long theYear) {
	   if (theYear >= 1900)
		   year = theYear ;
	}
	
	public void setMonth(long theMonth) {
	   if ((theMonth > 0) && (theMonth < 13))
		   month = theMonth ;
	}
	
	public void setDays(long theDays) {
	   if ((theDays > 0) && (theDays <= 31))
		   days = theDays ;
	}

   public boolean isLeapYear(long year) {
   boolean returnValue = false ;
	
      if ((year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0)))
	      returnValue = true ;
      return returnValue ;
   }
  
   public int returnDaysInYear(long year) {
	int returnValue = 365 ;
	
	   if (isLeapYear(year))
	      returnValue = 366;
	   return returnValue ;  
	}
	
	public int returnDaysInMonth(long year, long month) {
	int returnValue = 31 ;
	
	   if (month == 2)
		   if (isLeapYear(year))
			   returnValue = 29 ;
			else
			   returnValue = 28 ;
		if ((month == 4) || (month == 6) || (month == 9) || (month == 11))
		   returnValue = 30 ;
		return returnValue ;
	}
	
	public long returnJulianDate() {	
	   return julianDate ;
	}
	
	public long returnJulianDate(long year, long month, long day) {
	long aMonth = 0 ;
	long aYear = 0 ;
	long elapsedDaysInMonth = 0 ;
	long elapsedDaysInYear = 0 ;
	long julianDate = 0 ;

      aYear = 1900 ;
		while (aYear < (year)) {
		   elapsedDaysInYear = elapsedDaysInYear + returnDaysInYear(aYear) ;
			aYear++ ;
		}
		
		aMonth = 1 ;
	   while (aMonth < (month)) {
		   elapsedDaysInMonth = elapsedDaysInMonth + returnDaysInMonth(year, aMonth) ;
			aMonth++ ;
		} 
		
		julianDate = elapsedDaysInYear + elapsedDaysInMonth + day ;
		return julianDate ;		
	}
	
	public long returnYears() {
	long aYear ;
	long jd = julianDate ;
	
	   for (aYear = 1900 ; jd >= returnDaysInYear(aYear) ; aYear++)
		   jd = jd - returnDaysInYear(aYear) ;
			
		return aYear ;				
	}
	
	public long returnMonths() {
	long aMonth  ;
	long aYear = 1900 ;
	long jd = julianDate ;
	
	   for (aMonth = 1 ; jd >= returnDaysInMonth(aYear, aMonth) ; aMonth++) {
		   jd = jd - returnDaysInMonth(aYear, aMonth) ;
			if (aMonth == 12) {
			   aYear++ ;
			   aMonth = 0 ;
			}
		}	
			
		return aMonth ;
	}
	
	public long returnDays() {
	long aYear  ;
	long aMonth ;
	long day ;
	long jd = julianDate ;
	
	   for (aYear = 1900 ; jd >= returnDaysInYear(aYear) ; aYear++)
		   jd = jd - returnDaysInYear(aYear) ;
			
		for (aMonth = 1 ; jd >= returnDaysInMonth(aYear, aMonth) ; aMonth++)
		   jd = jd - returnDaysInMonth(aYear, aMonth) ;
	 		
		day = jd ;
		
		return day ;
	}
	
}   

public class DateMain {

   public static void main (String[] args) {
	Date aDate = null ;
	
	   aDate = new Date() ;
		
      System.out.println("Number of days since Jan 1,1900: " + aDate.returnJulianDate()) ; 
		System.out.println("Year of the julian date: " + aDate.returnYears()) ;
      System.out.println("Month of the julian date: " + aDate.returnMonths()) ;
		System.out.println("Day of the julian date: " + aDate.returnDays()) ;

	}
	
}