public class ListTest {
  public static void main(String[] args) {
    SLL x = new SLL();
    x.prepend(new Integer(4));
    x.prepend(new Integer(3));
    x.prepend(new Integer(2));
    x.prepend(new Integer(1));
    x.display();
    
  }
}


class SLL {
    private ListNode head;

    public SLL() { }

    public String toString() {
        if (head==null) return null;
        return head.toString();
    }

    public void display() {
        System.out.println(head);
    }

    public ListNode getHead() { return head; }
    
    public void prepend(Object o) {
      if (head == null)
        head = new ListNode(o,null);
      else
        head = new ListNode(o,head);
    } 
}
class ListNode {    
    private Object item;
    private ListNode next;
    public ListNode(Object o, ListNode n) {
        item = o;
        next = n;
    }
    public Object getItem() { return item; }
    public ListNode getNext() { return next; }
    public void setItem(Object o) { item = o; }
    public void setNext(ListNode n) { next = n;  }
    public String toString() {
        String temp = item.toString();
        if (next != null) temp += "->" + next.toString();
        return temp;
    }
}