Newby question :Null Pointer Exception Error

Rouzbelious

Hey folks, I am trying to write a code that draws a circle on every point that mouse is pressed and when mouse is released the circle moves to center of screen and merges with a big circle in the center. I wrote its code without any class objects and it works fine( 1st code) but when I try to write it with class objects(2nd code in comments) I face Null Pointer Exception error and I am almost sure that I have initialized all variables. I would appreciate if you tell me what is wrong.

int r;
int R = 100;
int RL = 100;
int x;
int y;
void setup() {
  size(800, 800);
  smooth();
  background(255);
  noStroke();
  frameRate(30);
  ellipseMode(CENTER);
}
void draw() {
  background(255);
  fill(80);
  ellipse(width/2, height/2, R, R);
  if (mousePressed) {
    fill(0);
    r++;
    x = mouseX;
    y = mouseY;
    ellipse(x, y, r, r);
  } else {
    fill(80);
    x += (width/2-x)*.05;
    y += (height/2-y)*.05;
    ellipse(x, y, r, r);
    if (abs(x-(width/2))<20 && abs(y-(height/2))<20 && r>0) {
      R++;
      ellipse(width/2, height/2, R, R);
      if (R == RL+r) {
        RL = R;
        r = 0;
      }
    }
  }
  println(r);
}

Rouzbelious

And this a the code with problem:

int R = 100;
mCircle Circle;

void setup() {
  size(800, 800);
  smooth();
  background(255);
  noStroke();

  frameRate(30);
  ellipseMode(CENTER);
  ellipse(width/2, height/2, R, R);
}

void draw() {
  background(255);
  if (mousePressed) {

     Circle.create();
     Circle.move();
  }
}

class mCircle {
  int r = 1;
  int x;
  int y;
  void create() {
    x = mouseX;
    y = mouseY;
    ellipse(x, y, r, r);
    r++;
  }

  void move() {
    x += (width/2-x)*.05;
    y += (height/2-y)*.05;
    ellipse(x, y, r, r);
  }
}

koogs

edit post, highlight code, press ctrl-o to format.

Null Pointer Exception FAQ:

https://forum.processing.org/two/discussion/8071/why-do-i-get-a-nullpointerexception

koogs

where do you instantiate Circle?

Rouzbelious

where do you instantiate Circle?

In line 2 at the top.

koogs

no, that defines it, doesn't instantiate it. println(Circle); will show that it's null and so line 19 is a NPE.

somewhere (setup()) you need Circle = new mCircle();. read the link.

also, read up on java naming convention because you've got it all backwards.

Rouzbelious

Thank you koogs!