How to properly display contents of a shared array within objects

Question

I'm having a difficult time figuring how to display the shared personArray with the appropriate course object. For example, I need to display a list of a course and the people that are in that course, and again for the next course. I feel that there's something wrong with my nested for loop or the personCount variable because not every course has the same amount of people so how do I deal with this?

Hopefully you all can get a clear picture of the stripped down code below.

Note* I must use aggregation and toStrings, and not allowed to use lists, arraylists, or scanner.

Thanks!

public class School {

    private static Course[] courseArray = new Course[5];

    public static void printList(){
        String print = "";
            for (int x = 0; x < courseCount; x++) {
                print += courseArray[x].getCourseName() + "\n";

                        for (int y = 0; y < personCount; y++){
                            print += courseArray[y].personArray[y].getPersonName()+ "\n";
                                               //^ I thought I could use the 1st forloop index to stay in the 1 course and print out all the people for that course(like the hardcode example below) but I get a nullpointer
                        }
                    }
                    JOptionPane.showMessageDialog(null,print);

/*      
  If I hardcode the print String like below I get the correct output. 
  So I know my objects are being stored properly, but I can't figure out how to get the correct display with a loop         
    print +=  courseArray[0].personArray[0].getPersonName(); //tim (bio)
    print +=  courseArray[0].peopleArray[1].getPersonName(); //bob (bio)
    print +=  courseArray[1].peopleArray[2].getPersonName(); //john (art)
*/          

    }                   
}
------------------------
public class Course { 

    private Person[] personArray = new Person[50]; 

    //constructor for course

    // get/set courseName methods

    public String toString(){
        // not sure how to use this the right way
    }
}
-----------------------------------
public class Person extends Course {

    //constructor for person

    // get/set personName methods

    public String toString(){
        return getPersonName();
    } 
}

Answer 1

Make sure that all 50 of the people in your personArray are initialized first; check to see if they are by printing out the entire array like so (you will need to import java.util.Arrays):

System.out.println(Arrays.toString(course[x].personArray));

If that gives back any "null" values then you know that not every single Person in the PersonArray was initialized first.

Answer 2

You should change courseCount to courseArray.length and personCount to courseArray.getPersonArraySize() and implement getPersonArraySize() in Course class to return length of personArray.

Answer 3

replace your loops with these below..

for (Course c : courseArray) {

   print += c.getCourseName() + "\n";

   for (Person p : c.personArray){

     print += p.getPersonName()+ "\n";

    }
}