Merge two Sorted linked lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

代码如下：

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if(l1 == null) return l2;        if(l2 == null) return l1;                if(l1.val < l2.val){            l1.next = mergeTwoLists(l1.next,l2);            return l1;        }else{            l2.next = mergeTwoLists(l1,l2.next);            return l2;        }            }}