Car[] cars = new Car[100];

void setup(){
  size(1000,600);
  smooth();
  
  for (int i = 0; i < cars.length; i++){
    cars[i] = new Car(color(i*2),0,i*2,i/20.0);
  }
}

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

class Car{
  color c;
  float xpos;
  float ypos;
  float xspeed;
  
  Car(color c_, float xpos_, float ypos_, float xspeed_){
    c = c_;
    xpos = xpos_;
    ypos = ypos_;
    xspeed = xspeed_;
  }
  
  void display(){
    rectMode(CENTER);
    stroke(0);
    fill(c);
    rect(xpos,ypos,20,10);
  }
  
  void move(){
    xpos = xpos + xspeed;
    if (xpos > width){
      xpos = 0;
    }
  }
}