21.merge 2 sorted list

public ListNode mergeTwoList(ListNode l1,ListNode l2){
   ListNode dummy = new ListNode(0);
   ListNode cur  = dummy;
   while(l1!=null&&l2!=null){
   if(l1.val<l2.val){
      cur.next = l1;
      l1 = l1.next;
   }
   else{
      cur.next = l2;
      l2 = l2.next;
   }
      cur = cur.next;
   }
  cur.next = (l1!=null)?l1:l2;
  return dummy.next;

}