//An instance of this class represents a day of the Gregorian Calendar
//
public class CalendarDay
{
   //Class Constants
   public static final int MIN_DAY_NUMBER = 1;
   public static final int MAX_DAY_NUMBER = 31;
   
   //Instance (State) Variable
   private int number;  //1 .. 31
   
   //Constructor
   public CalendarDay(int number)
   {
      if ( false )   //Test for an invalid Day number
         throw new RuntimeException("Invalid Day # " + number);
      
   }
   
   //Accessor

}