Simple linked list with tail addition

MyList.scala

package excercises

abstract class MyList {
  def head(): Int
  def tail(): MyList
  def isEmpty: Boolean
  def add(element: Int): MyList

  def printElements: String

  override def toString: String = "[" + printElements + "]"
}

object Empty extends MyList {
  override def head(): Int = throw new NoSuchElementException
  override def tail(): MyList = throw new NoSuchElementException
  override def isEmpty: Boolean = true
  override def add(element: Int): MyList = new Cons(element, Empty)
  override def printElements: String = ""
}

class Cons(head: Int, tail: MyList) extends MyList {
  override def head(): Int = head
  override def tail(): MyList = tail
  override def isEmpty: Boolean = false
  override def add(element: Int): MyList =
    if(tail.isEmpty) new Cons(head, new Cons(element, tail))
    else new Cons(head, tail.add(element))
  override def printElements: String =
    if(tail.isEmpty) "" + head
    else head + " " + tail.printElements
}

object CreatingLinkedList extends App {
  val list = new Cons(1, Empty)
  println(list.toString)
  val listTwo = list.add(2).add(3).add(4)

  println(listTwo.toString)
}