int numBoxes = 1000;
ArrayList boxes = new ArrayList();

void setup() { 
  size(600, 500, JAVA2D);
  for(int i = 0; i<numBoxes; i++)
    boxes.add(new Box(random(width),random(height)));
}
void draw() {
  background(128);
  for(int i = 0; i<boxes.size(); i++)
    ((Box)boxes.get(i)).step();
  if(frameCount % 10 == 0)
    println("frameRate="+frameRate+" frameCount="+frameCount);
}

class Box {
  color c = color(255,255,0);
  float x, y;
  Box(float x, float y) {
    this.x = x;
    this.y = y;
  }
  void step(){
    x = max(min(x+random(-1,1),width),0);
    y = max(min(y+random(-1,1),height),0);
    paint();
  }
  void paint(){
    noStroke();
    fill(c);
    rect(x-2,y-2,5,5);
  }
}

/**
 * Test of Processing with a very simple model. 
 * Create 1000 instances of a local Box class.  Every frame have each box jiggle by a random amount.
 */