while(!turtles.isEmpty()){

    for(Iterator<RaceTurtle> it = turtles.Iterator(); it.hasNext();){

            RaceTurtle turtle = it.next();

            RaceWindow.delay(10);

            if(turtle.getX()>=RaceWindow.X_END_POS){
                    turtles2.add(turtle);
                    it.remove();
            }
    }
}