Question

I have a problem with this piece of code:

PointerCoords[][]srodki = new PointerCoords[n2][];

for(int i = 0; i < n2; i++)
{
        srodki[i] = new PointerCoords[n2];
}

for(int i = 0; i < n2; i++)
{
        for(int j = 0; j < n2; j++)
        {
                srodki[i][j].y = r + j*k;
                srodki[i][j].x = r + i*k;
        }

}

Why do I get a NullPointerException?

Answer 1

The problem is that you didn’t initialize the content of
srodki[i][j] before performing the insertion:

srodki[i][j].y = r + j*k;
srodki[i][j].x = r + i*k;

So first, you need to perform:

srodki[i][j] = new PointerCoords();

and then it shall be ok.