int numObj = 10;
Objects[]obj = new Objects[numObj];

void setup(){
  background(255);
  size(800, 800);
  
}

void draw(){
  background(255);
  placeObj();
}

void placeObj(){
  for(int i = 0; i < numObj; i++){
    obj[i] = new Objects();
    obj[i].display();
  }
}

void keyPressed(){
  if(key == CODED){
    if(keyCode == UP){
	numObj++;
	obj = new Objects[numObj];
    }
    if(keyCode == DOWN){
	numObj--;
	if(numObj < 1){
	  numObj = 0;
	}
	obj = new Objects[numObj];
	
    }
  }
}

class Objects{
  float x, y;
  boolean drawn;
 
  
  void display(){
    if(drawn != true){
	chooseRndLoc();
    }
    noFill();
    smooth();
    pushMatrix();
    translate(x, y);
    ellipse(0,0,20,20);
    drawn = true;
    popMatrix();
  }
  void chooseRndLoc(){
	if(drawn != true){
	  float rndX = random(20, width -20);
	  float rndY = random(20, height - 20);
	  x = rndX;
	  y = rndY;
     }
  }
}