problem with a program I wrote

[1student]

Hi,

I wrote a problem in Java - quite a long one.
I succeeded to compile it, but when I ran it there were run time exceptions.

Here are the messages I've got:

java.lang.NullPointerException
at SparseMatrix.addStudent(SparseMatrix.java:29)
at SparseMatrix.main(SparseMatrix.java:196)

java.lang.NullPointerException
at SparseMatrix.addCourse(SparseMatrix.java:37)
at SparseMatrix.main(SparseMatrix.java:203)


I would like you to help me find the cause of the problem...

The program I wrote is as follow:
(I indicated the lines Java didn't get).

 

[MrChad]

Why do you initialize the rows and columns arrays with new Cell objects and then set them to null?

for(int i=0; i<numC; i++)
...{
......rows[ I]=new Cell(i,0);
......rows[ I]=null;
......cols[ I]=new Cell(0,i);
......cols[ I]=null;
...}

 

[1student]

Is it super place?

Also when I delete it, it doesn't work..

 

[Yomicron]

Originally posted by: 1student
Is it super place?

Also when I delete it, it doesn't work..

Setting the rows and columns to null is only part of the problem. In your Cell class you never initilize Student 's' and Course 'c'.

 

[1student]

I tried to initialize the variables, but it doesn't work yet.
I get that message:

found : SparseMatrix.Course
required: int
c=new Course();
^
1 error

Where is the mistake now?
Here is the program: