leetcode--Merge Two Sorted 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.

/** * 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) {        ListNode head = new ListNode(-1); ListNode p = head;     while(l1!=null && l2!=null){     if(l1.val<l2.val){     p.next = new ListNode(l1.val);     p = p.next;     l1 = l1.next;     }else{     p.next = new ListNode(l2.val);     p = p.next;     l2 = l2.next;     }     }     if(l1!=null){     p.next = l1;     }     if(l2!=null){     p.next = l2;     }     return head.next;    }}