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.

/**
* Created by ustc-lezg on 16/4/7.
*/
public class Solution {

public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
ListNode ptr = new ListNode(0);
ListNode head = ptr;
while (l1 != null && l2 != null) {
if (l1.val <= l2.val) {
ptr.next = l1;
l1 = l1.next;
}else {
ptr.next = l2;
l2 = l2.next;
}
ptr = ptr.next;
}
if (l1 != null) {
ptr.next = l1;
}
if (l2 != null) {
ptr.next = l2;
}
return head.next;
}

}