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. }

1(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 leapYears = 0;
  
  for(int y = year1; y <= year2; y++)
    if(isLeapYear(y))
      leapYears++;
  
  return leapYears;
}

1.

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.

Class information for this question

• public class APCalendar
• private static boolean isLeapYear(int year)
• public static int numberOfLeapYears(int year1, int year2)
• private static int firstDayOfYear(int year)
• private static int dayOfYear(int month, int day, int year)
• public static int dayOfWeek(int month, int day, int year)

1(b)

Complete method dayOfWeek below. You must use firstDayOfYear and dayOfYear appropriately to receive full credit.

/** 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 static int dayOfWeek(int month, int day, int year)
{
  int weekday = firstDayOfYear(year);
  int additionalDays = dayOfYear(month, day, year) - 1;

  for(int d = 1; d <= additionalDays; d++)
  {
    weekday++;

    if(weekday == 7)
      weekday = 0;
  }
        
  return weekday;
}

• A for loop is a repetition control structure that allows you to efficiently write a loop that needs to be executed a specific number of times.
• A for loop is useful when you know how many times a task is to be repeated.