A. Implement a superclass called Appointment and subclasses OneTime, Daily, Weekly, and Monthly. An Appointment has a description (for example, “Meet with interviewer about jobâ€) and a date and time. Write a method occursOn(int year, int month, int day) that checks whether the appointment occurs on that date. For example, for a monthly appointment, you must check whether the day of the month matches. Then, in a TestAppointment class, fill an array of Appointment objects with a mixture of different kinds of appointments. Ask a user to enter a date and print out all appointments that occur on that date.

B. Improve your Appointment program by giving the user the option to add new Appointments. The user must specify the type of the appointment, the description, and the date and time.

C. Improve the program further by letting the user save the appointment data to a file and reload the data from a file. The saving part is straightforward: make a method saveApptData. In it, save the type, description, date, and time to a file. The loading part is not so easy. First determine the type of the appointment to be loaded, create an object of that type, and then call a loadApptData method to load the data.

As always, the source code must be indented properly and contain comments that describe important parts of the algorithm.