1. The APCalendar class contains methods used to calculate information about a calendar. You will write two methods of the class.
public class APCalendar
{
 /** Returns true if year is a leap year and false otherwise. */
 private static boolean isLeapYear(int year)
 { /* implementation not shown */ }
 /** Returns the number of leap years between year1 and year2, inclusive.
 * Precondition: 0 <= year1 <= year2
 */
 public static int numberOfLeapYears(int year1, int year2)
 { /* to be implemented in part (a) */ }
 /** Returns the value representing the day of the week for the first day of year,
 * where 0 denotes Sunday, 1 denotes Monday, ..., and 6 denotes Saturday.
 */
 private static int firstDayOfYear(int year)
 { /* implementation not shown */ }
 /** Returns n, where month, day, and year specify the nth day of the year.
 * Returns 1 for January 1 (month = 1, day = 1) of any year.
 * Precondition: The date represented by month, day, year is a valid date.
 */
 private static int dayOfYear(int month, int day, int year)
 { /* implementation not shown */ }
 /** Returns the value representing the day of the week for the given date
 * (month, day, year), where 0 denotes Sunday, 1 denotes Monday, ...,
 * and 6 denotes Saturday.
 * Precondition: The date represented by month, day, year is a valid date.
 */
 public static int dayOfWeek(int month, int day, int year)
 { /* to be implemented in part (b) */ }
 // There may be instance variables, constructors, and other methods not shown.
}

(a) Write the static method numberOfLeapYears, which returns the number of leap years between year1 and year2, inclusive. In order to calculate this value, a helper method is provided for you.

  • isLeapYear(year) returns true if year is a leap year and false otherwise. Complete method numberOfLeapYears below. You must use isLeapYear appropriately to receive full credit. /** Returns the number of leap years between year1 and year2, inclusive.
    • Precondition: 0 <= year1 <= year2 */ public static int numberOfLeapYears(int year1, int year2)
public static int numberOfLeapYears(int year1, int year2)
{  
   int numLeapYears = 0;  //intializes the variable numLeapYears starting at 0
   for (int i = year1; i <= year2; i++) { //incriments the value by 1
       if (isLeapYear(i)) { 
           numLeapYears ++;  //checking how many leap years happen between the two years 
       }
   }
   return numLeapYears; //ends the function

}

(b) Write the static method dayOfWeek, which returns the integer value representing the day of the week for the given date (month, day, year), where 0 denotes Sunday, 1 denotes Monday, ..., and 6 denotes Saturday.

For example, 2019 began on a Tuesday, and January 5 is the fifth day of 2019. As a result, January 5, 2019, fell on a Saturday, and the method call dayOfWeek(1, 5, 2019) returns 6.

As another example, January 10 is the tenth day of 2019. As a result, January 10, 2019, fell on a Thursday, and the method call dayOfWeek(1, 10, 2019) returns 4.

In order to calculate this value, two helper methods are provided for you.

  • firstDayOfYear(year) returns the integer value representing the day of the week for the first day of year, where 0 denotes Sunday, 1 denotes Monday, ..., and 6 denotes Saturday. For example, since 2019 began on a Tuesday, firstDayOfYear(2019) returns 2.

  • dayOfYear(month, day, year) returns n, where month, day, and year specify the nth day of the year. For the first day of the year, January 1 (month = 1, day = 1), the value 1 is returned. This method accounts for whether year is a leap year. For example, dayOfYear(3, 1, 2017) returns 60, since 2017 is not a leap year, while dayOfYear(3, 1, 2016) returns 61, since 2016 is a leap year.

public static int dayOfWeek(int month, int day, int year)
 {  
    int firstDay = firstDayOfYear(year);  //initializes the firstDay as the firstDayOfYear
    int theDate = dayOfYear(month, day year); //finds the day of the year
    int theDay = (firstDay + theDate - 1) % 7; //calculates the day of the year from the first day
    return theDay; //ends the function
}

Complete method dayOfWeek below. You must use firstDayOfYear and dayOfYear appropriately to receive full credit. GO ON TO THE NEXT PAGE.

/** Returns the value representing the day of the week for the given date

  • (month, day, year), where 0 denotes Sunday, 1 denotes Monday, ...,
  • and 6 denotes Saturday.
  • Precondition: The date represented by month, day, year is a valid date. */ public static int dayOfWeek(int month, int day, int year)
public class APCalendar
{
 /** Returns true if year is a leap year and false otherwise. */
 private static boolean isLeapYear(int year)
 { /* implementation not shown */ }
 /** Returns the number of leap years between year1 and year2, inclusive.
 * Precondition: 0 <= year1 <= year2
 */
 public static int numberOfLeapYears(int year1, int year2)
 { /* to be implemented in part (a) */ 
    int numLeapYears = 0;
    for (int i = year1; i <= year2; i++) {
        if (isLeapYear(i)) {
            numLeapYears ++;
        }
    }
    return numLeapYears; 

}
 /** Returns the value representing the day of the week for the first day of year,
 * where 0 denotes Sunday, 1 denotes Monday, ..., and 6 denotes Saturday.
 */
 private static int firstDayOfYear(int year)
 { /* implementation not shown */ }

 /** Returns n, where month, day, and year specify the nth day of the year.
 * Returns 1 for January 1 (month = 1, day = 1) of any year.
 * Precondition: The date represented by month, day, year is a valid date.
 */
 private static int dayOfYear(int month, int day, int year)
 { /* implementation not shown */ }

 /** Returns the value representing the day of the week for the given date
 * (month, day, year), where 0 denotes Sunday, 1 denotes Monday, ...,
 * and 6 denotes Saturday.
 * Precondition: The date represented by month, day, year is a valid date.
 */
 public static int dayOfWeek(int month, int day, int year)
 {  
    int firstDay = firstDayOfYear(year);
    int theDate = dayOfYear(month, day year);
    int theDay = (firstDay + theDate - 1) % 7;
    return theDay;
 }
 // There may be instance variables, constructors, and other methods not shown.
}