Merge Two Sorted Lists

Merge two sorted (ascending) linked lists and return it as a new sorted list. The new sorted list should be made by splicing together the nodes of the two lists and sorted in ascending order.

public class Solution {    /**     * @param ListNode l1 is the head of the linked list     * @param ListNode l2 is the head of the linked list     * @return: ListNode head of linked list     */    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        ListNode dummy = new ListNode(0);        ListNode lastNode = dummy;        while (l1 != null && l2 != null) {            if (l1.val < l2.val) {                lastNode.next = l1;                l1 = l1.next;            } else {                lastNode.next = l2;                l2 = l2.next;            }            lastNode = lastNode.next;        }        if (l1 != null) {            lastNode.next = l1;        }        if (l2 != null) {            lastNode.next = l2;        }        return dummy.next;    }}