Hi there !

Still working on my li'll project and still getting lot's of errors, thanks to your help, I went throw a lot of them (and my code get lighter ^^), but there still new incomers -_-

so here it is, the new one : I get a NullPointException error on the boule[0].x=100 (and I think it's the same for all the other boule[0,1].y,r,m etc... above it). I looked for other thread about this error but didn't manage to find the solution in this case, so If you have some time, could you have a look please ?

Here is the code (if neeeded I can also display the boule class code, I don't know if it can be related to)

Code:

Boule[] boules = new Boule[20];


int width = 400 ;
int height = 400 ;


float gravite;



void setup() {
  size(width,height);
  smooth();
  
  boules[0].x=100;
  boules[1].x=150;
  
  boules[0].y=150;
  boules[1].y=220;
  
  boules[0].r=50;
  boules[1].r=12;
  
  boules[0].m=7;
  boules[1].m=1;
  
 
  
 
  gravite = .015;
}

void draw() {
  background(255);
}
  
void create(){
  for(int i=0; i<boules.length; i++){
     boules[i] = new Boule(boules[i].r,boules[i].x,boules[i].y,boules[i].m,i);
  }
}
  
void bounce(){
  for(int i=0; i<boules.length; i++){
     boules[i].action();
  
 }
}
 

actually just try this:

change
Boule[] boules = new Boule[20];
to
Boule[] boules;

and add in setup() this:
boules = new Boule[20];

Hi there ! thanks for your help

I modified the main code, in fact the create() wasn't needed I think (cause I already got a similar fonction in the class code) so I removed it for the draw part, and put a part of it in the setup to initialize correctly values, did I do it in the right way ? )
also, I modified my array declaration as you told me, but I still got the same error (NullPointerException) so I'm a bit lost °-° , anyway here the code :

Main Part :

Code:

Boule[] boules;



float gravite;



void setup() {
  size(400,400);
  smooth();
  boules = new Boule[20];
  
  boules[0].x=100;
  boules[1].x=150;
  
  boules[0].y=150;
  boules[1].y=220;
  
  boules[0].r=50;
  boules[1].r=12;
  
  boules[0].m=7;
  boules[1].m=1;
  
  for(int i=0; i<boules.length; i++){
  boules[i] = new Boule(boules[i].r,boules[i].x,boules[i].y,boules[i].m,i);
  }
  
  gravite = .015;
}

void draw() {
  background(255);
  for(int i=0; i<boules.length; i++){
     boules[i].action();
  
 }
} 

and Boule class Part :

Code:

class Boule {
  
  float r;    // rayon
  float x,y; // position
  
  int index;
 
  color c = color(0,0);
  
  float xv = 0;	 //vélocité actuelle le long de l'axe des x
  float yv = 0;	 //vélocité actuelle le long de l'axe des y
  
  float xd;	  
  float yd;	  
  float d;   
  
  float gAngle;   
  float gTheta;   //angle en radians
  float gxv;	// gravité en x
  float gyv;	// gravité en y
  float m;	// masse particule
  
  Boule(float r_init, float x_init, float y_init, float m_init, int i_init) {
   x	= x_init;
   y	= y_init;
   r	= r_init;
   
   index  = i_init;
   
   m	= m_init;
   } 

void action(){
  appliquerGravite();
  bouge();
  rebondir_ecran();
  allume();
  dessine();
}
  


void appliquerGravite(){
  for(int i=0; i<boules.length; i++){
    if (i != index ){
    gAngle     = calculAngle(x, y, boules[i].x, boules[i].y);
    gTheta     = (-(gAngle * PI))/180;
    gxv	  = cos(gTheta) * (-gravite/(r/6));
    gyv	  = sin(gTheta) * (-gravite/(r/6));
    
    
    boules[i].xv += m*boules[i].gxv;
    boules[i].yv += m*boules[i].gyv;
    xv += m*gxv;
    yv += m*gyv;
  }
  }
}
    
    void bouge(){
    
    x	 +=   xv; 
    y	 +=   yv;
    
  }
     
  void rebondir_ecran(){
  
	 if (x > width-50){
	   xv = xv-(4/r);}
	 if(x < 50){
	   xv = xv+(4/r);}
	  
	 if (y > height-50){ 
	   yv = yv-(4/r);}
	 if(y < 50){
	   yv = yv+(4/r);}
	 }
   
   

   void allume (){
     for(int i=0; i<boules.length; i++){
    if (i != index ){
   
  c = color(150,50);
  xd = x - boules[i].x; 
  yd = y - boules[i].y; 
    }
   }
  }
   
 
  
  void dessine () {
   
   noStroke();
   fill(c);
   ellipse(x,y,r*2,r*2);
   c = color(0,0,0,128);
	}
	
float calculDistance(float x1, float y1, float x2, float y2){ 
  xd = x1 - x2; 
  yd = y1 - y2; 
  d = sqrt(xd * xd + yd * yd); 
  return d; 
  
} 


 float calculAngle ( float x1, float y1, float x2, float y2){
    float  xd = x1 - x2  ;
    float  yd = y1 - y2   ;
  
float t = atan2 (yd,xd);
float a =(180 + (-(180*t) / PI));
return a;
}
} 

thanks for your answer ^^

I did just as you said, so now it's like this :

Code:

Boule[] boules;


float gravite;



void setup() {
  size(400,400);
  smooth();
  boules = new Boule[20];
  
   for(int i=0; i<boules.length; i++){
  boules[i] = new Boule(boules[i].r,boules[i].x,boules[i].y,boules[i].m,i);
  }
  
  boules[0].x=100;
  boules[1].x=150;
  
  boules[0].y=150;
  boules[1].y=220;
  
  boules[0].r=50;
  boules[1].r=12;
  
  boules[0].m=7;
  boules[1].m=1;
  
 
  
  gravite = .015;
}

void draw() {
  background(255);
  for(int i=0; i<boules.length; i++){
     boules[i].action();
  
 }
} 

but I still got a NullPointerException °_° but the error moved to this line :

Code:

boules[i] = new Boule(boules[i].r,boules[i].x,boules[i].y,boules[i].m,i); 

Am I cursed XD ?

in fact, what does mean the NullPointerException ?

edit :

finally I managed to make it work, but by removing some controls. I removed all the way to control values of each Boule object by doing this :

Code:

Boule[] boules;



float gravite;



void setup() {
  size(400,400);
  smooth();
  boules = new Boule[5];
  
   for(int i=0; i<boules.length; i++){
     float dr = random(5,50);
     float dx = random(width);
     float dy = random(height);
     float dm = random(1,10);
  boules[i] = new Boule(dr,dx,dy,dm,i);
  }
  
 
  
 
  
  gravite = .015;
}

void draw() {
  background(255);
  for(int i=0; i<boules.length; i++){
     boules[i].action();
  
 }
} 

but now I got to find a way to put back correctly controls on Boule object like boule[i].x = 100 etc... for the moment I didn't find out how to do it, and get back NullPointerException, Do You have any idea of the way to do it properly ?

for example, by restarting on the working version I tried this way but get back NullPointerException on the
Code:

float dr = boules[i].r; 

it seems that processing don't like boule[i]."some variable", but I don't know why.

here is it :
Code:

Boule[] boules;


float gravite;



void setup() {
  size(400,400);
  smooth();
  boules = new Boule[2];
  
   for(int i=0; i<boules.length; i++){
     float dr = boules[i].r;
     float dx = boules[i].x;
     float dy = boules[i].y;
     float dm = boules[i].m;
     
     boules[0].r = 10;
     boules[0].x = 100;
     boules[0].y = 10;
     boules[0].m = 3;
     
     boules[1].r = 25;
     boules[1].x = 250;
     boules[1].y = 300;
     boules[1].m = 3;
     
  boules[i] = new Boule(dr,dx,dy,dm,i);
  }
  
 
  
 
  
  gravite = .015;
}

void draw() {
  background(255);
  for(int i=0; i<boules.length; i++){
     boules[i].action();
  
 }
}
 

Ah, I was about to advise not to init your arrays this way, before seeing your question... :-D

Simple way: float[] x = new float[20]; // Adjust value, of course
By default, arrays of primitive values (int, long, float, double, boolean, char...) are initialized to 0 (false for booleans).

And to answer the second question: a NPE (NullPointerException) happens frequently. Particularly when you use a method or access a field of an object which hold a null value (ie. isn't set):
foo.x or foo.getX() will throw such exception because foo is null, and thus you cannot access anything in it.