# Problem in coding can't understand it
**URL:** https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363
**Category:** Coding Questions
**Created:** [December 13, 2019, 6:57am UTC](https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363 "2019-12-13T06:57:27Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@NourAdel205](https://discourse.processing.org/u/NourAdel205)
#### Post date: [December 13, 2019, 6:57am UTC](https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363/1 "2019-12-13T06:57:27Z")
## so i coded this to allow me to make planets around the sun but it gives me error
THE CODE:-
```auto
planet sun;
planet earth;
void setup(){
size (1000,1000);
sun= new planet(width/2,height/2,40,#FFBC13);
earth=new planet(sun,0,400,10,#159CEE);
}
void draw(){
background(0);
sun.display();
earth.display();
}
```
OTHER TAB:-
```auto
class planet{
planet other;
color average;
float diameter;
float distance;
float speed;
float x=other.x+cos(speed)*distance;
float y=other.y+sin(speed)*distance;
planet(float tempX,float tempY,float tempDiameter,color tempColor){
x=tempX;
y=tempY;
diameter=tempDiameter;
average=tempColor;
}
planet(planet tempOther,float tempSpeed,float tempDistance,float tempDiameter,color tempColor){
other=tempOther;
speed=tempSpeed;
distance=tempDistance;
diameter=tempDiameter;
average=tempColor;
}
void display(){
noStroke();
fill(average);
ellipse(x,y,diameter,diameter);
}
}
```
* * *
when i execute it
it gives me this error
> java.lang.NullPointerException: Attempt to read from field ‘float processing.test.planets2.Planets2$planet.x’ on a null object reference
> at processing.test.planets2.Planets2$planet.(Planets2.java:37)
> at processing.test.planets2.Planets2.setup(Planets2.java:23)
> at processing.core.PApplet.handleDraw(PApplet.java:1801)
> at processing.core.PSurfaceNone.callDraw(PSurfaceNone.java:471)
> at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:503)
> java.lang.NullPointerException: Attempt to read from field ‘float processing.test.planets2.Planets2$planet.x’ on a null object reference
> at processing.test.planets2.Planets2$planet.(Planets2.java:37)
> at processing.test.planets2.Planets2.setup(Planets2.java:23)
> at processing.core.PApplet.handleDraw(PApplet.java:1801)
> at processing.core.PSurfaceNone.callDraw(PSurfaceNone.java:471)
> at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:503)
---
### Author:  [@Waboqueox](https://discourse.processing.org/u/Waboqueox)
#### Post date: [December 13, 2019, 7:58am UTC](https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363/2 "2019-12-13T07:58:44Z")
🤔 You get the error because here:
> [@NourAdel205](#):
>
> float x=other.x+cos(speed)\*distance;
> float y=other.y+sin(speed)\*distance;
💡You are trying to create a class with parameters that doesn’t exit yet.
Here you are a possible solution, also the code formatted, remember to format your code with the \ button please 😃
> **Example running**
>
> ```auto
> Planet sun,earth;
>
> void setup(){
> size (1000,1000);
> sun= new Planet(width/2,height/2,40,#FFBC13);
> earth=new Planet(sun,0.01,400,10,#159CEE);
> }
>
> void draw(){
> background(0);
> sun.display();
> earth.display();
> }
>
> class Planet{
> Planet other;
> color average;
> float diameter;
> float distance;
> float speed;
> float x;//=other.x+cos(speed)*distance;
> float y;//=other.y+sin(speed)*distance;
>
> Planet(float tempX,float tempY,float tempDiameter,color tempColor){
> x=tempX;
> y=tempY;
> diameter=tempDiameter;
> average=tempColor;
> }
>
> Planet(Planet tempOther,float tempSpeed,float tempDistance,float tempDiameter,color tempColor){
> other=tempOther;
> speed=tempSpeed;
> distance=tempDistance;
> diameter=tempDiameter;
> average=tempColor;
> }
>
> void display(){
> noStroke();
> fill(average);
> ellipse(x,y,diameter,diameter);
> if(this.speed != 0){
> this.x = other.x+cos(speed)*distance;
> this.y =other.y+sin(speed)*distance;
> this.speed+=0.01;
> }
> }
> }
>
> ```
---
### Author:  [@NourAdel205](https://discourse.processing.org/u/NourAdel205)
#### Post date: [December 15, 2019, 6:04am UTC](https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363/3 "2019-12-15T06:04:32Z")
can you explain it more please
i cant understand how they dont exist yet
---
### Author:  [@Lexyth](https://discourse.processing.org/u/Lexyth)
#### Post date: [December 15, 2019, 8:54am UTC](https://discourse.processing.org/t/problem-in-coding-cant-understand-it/16363/4 "2019-12-15T08:54:47Z")
```auto
planet other; //this is null
color average; //null (or maybe just 0)
float diameter; //0
float distance; //0
float speed; //0
float x=other.x+cos(speed)*distance; //this is doing this :
//float x = null.x (which is nothing, not 0, nothing...) +... and the rest.
//you are trying to access the x of a planet that you never defined
//defining means other = new Planet(...); or other = jupiter; but you didn’t do this yet
//and your first constructor never actually does that , only the second one.
float y=other.y+sin(speed)*distance;
```
Also, @Waboqueox , i‘m not sure if the OP want the x and y to be updated, but maybe to only be relative to the other Planets first x and y when created.
```auto
class Planet{
Planet other;
color average;
float diameter;
float distance;
float speed;
float x;//=other.x+cos(speed)*distance;
float y;//=other.y+sin(speed)*distance;
Planet(float tempX,float tempY,float tempDiameter,color tempColor){
x=tempX;
y=tempY;
diameter=tempDiameter;
average=tempColor;
}
Planet(Planet tempOther,float tempSpeed,float tempDistance,float tempDiameter,color tempColor){
other=tempOther;
x=other.x+cos(speed)*distance;
y=other.y+sin(speed)*distance;
speed=tempSpeed;
distance=tempDistance;
diameter=tempDiameter;
average=tempColor;
}
void display(){
noStroke();
fill(average);
ellipse(x,y,diameter,diameter);
}
}
```