public class App {
  public static void main(String[] args) {
    // create the list 2 -> 1 -> 0
    List l = new List(0);
    for (int i = 1; i <= 4; i++) {
      l = l.prepend(i);
    }
    
    // recursively print elements of the list
    printList(l);
  }
  
  private static void printList(List l) {
    if (l != null) {
      System.out.println(l.getHead());
      printList(l.getTail());
    }
  }
}