public int numFives () {
    if (first.next == null) return 0;
    Node x = first;
    int result = 0;
    while (x.next != null) {
      if (x.item != 5.0) x = x.next;
      if (x.item == 5.0) {
        result = result + 1;
        x = x.next; 
      }
    }
    if (x.next == null && x.item == 5.0) {
      result = result + 1;
    }
    return result;
  }