I was trying to run a program but kept getting the error, NullPointerException. I simplified my code down to as simple as can be to see if I could figure out what the problem was but it still eludes me. I usually like to figure things out on my own but this is driving me crazy. Can any of you see the issue? The error appears in line which reads: "  rect(b.i, b.j, 100, 100); " inside the drawBox function.

void drawBox(thing b){
 
  rect(b.i, b.j, 100, 100);
 
}

class thing{
 
  int i;
  int j;
 
  thing(int ith, int jth){
    i = ith;
    j = jth;
  }
}

thing cube;

void setup(){
 
  size(600,600);
 
  thing cube = new thing(250, 250);
 
}

void draw(){
 
  drawBox(cube);
 
}