Calendar Class Problem

[Thomas338]

I'm trying to make an application to keep track of your appointments.
There are 2 classes, an Appointment class and a Calender class.
The Appointment class doesn't really matter for this question, so i'll just add the constructor of the Calender class.

public class Calender {


    private ArrayList<Appointment> appointments;
    private Calendar cal;
    private int date;
    private int month;
    private int year;


 public Calender() {
     appointments = new ArrayList<Appointment>();
     cal = Calendar.getInstance();
     this.date = cal.get(Calendar.DATE);
     this.year = cal.get(Calendar.YEAR);
     this.month = cal.get(Calendar.MONTH)+1;

The problem is I can't alter the date, and I need to do so for some of my methods.

simple example;

   public void addDay() {
       this.cal.add(Calendar.DATE, 1);
   }

i also tried, this.cal.roll(Calendar.DATE, true) and this.cal.set.(Calendar.DATE, 23)
asked my teacher why this doesn't work, but he doesn't seem to know either..

edit: I imported
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;

[KevinWorkman]

If you want help, you'll have to provide an SSCCE that demonstrates the problem. In other words, it should be as little code as possible while still being runnable (by simply copying and pasting the whole thing) and demonstrating the problematic behavior.

[hosscomp]

The problem is I can't alter the date, and I need to do so for some of my methods.

What you are showing will work if it is all in the right place. You need to show how you are calling it and the response you get.

[Tolls]

What are you trying this on?
Your Calender object, or a Calendar object?

From what you've posted your Calender class does not have an add() method, or a roll() method or a set() method.

Also when posting a problem you need to tell us the problem, including any error messages and stack traces you get.