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# Newby question :Null Pointer Exception Error

edited August 2017

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);
}
``````
Tagged:

• edited August 2017

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);
}
}
``````
• 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

• where do you instantiate Circle?

• where do you instantiate Circle?

In line 2 at the top.

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.