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.

}

Part 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.

1. isLeapYear(year) returns true if year is a leap year and false otherwise. 

Complete method numberOfLeapYears. You must use isLeapYear appropriately to receive full credit.