var i: Iterator[Int] = Iterator.empty

  def poll() = {
    while (i.hasNext) {
      println(i.next())
    }
    println("No more elements")
  }

  poll()
  println("here we have join iterator")
  i = i ++ Seq(1, 2, 3)
  poll()
  println("here we have concat iterator")
  i = i ++ Seq(4, 5, 6)
  poll()
  println("append to empty concate iterator")
  i = i ++ Seq(7, 8, 9)
  poll()
  println(i.hasNext)