Hi, here I share you a TINY class that simulate a urn object. I took (stole... as you wish lol) the idea from max/msp.

Urn is a random without duplication, thats it.

Here is the code, hope it'll be usefull for someone lol

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Urn __urn;

void setup(){
 __urn = new Urn(10);
}

void draw(){  
 int f = __urn.update();    
 if(f == -1) noLoop();//__urn.reset();  
 println(f); //print element took from urn  
}

class Urn{

 int maximum; //max array size
 int[] urn;
 int index; //current level

 Urn(int _maximum){
   maximum = _maximum;
   urn = new int[_maximum];
   for(int i = 0; i < maximum; i++) urn[i] = i;      
   reset();
 }

 void reset(){    
   index = maximum - 1;
 }

 int update(){
   if(index < 0) return -1;
   int randomIndex = floor(random(index));
   int returnValue = urn[randomIndex];
   urn[randomIndex] = urn[index];      
   urn[index] = returnValue;
   index--;
   return returnValue;
 }

}