LeetCode: 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.

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { *         val = x; *         next = null; *     } * } */public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        if(l1 == null && l2 == null) return null;        if(l1 != null && l2 == null) return l1;        if(l1 == null && l2 != null) return l2;        int lest = 0;        ListNode p1 = l1;        ListNode p2 = l2;        if(l1.val < l2.val) { lest = l1.val; p1 = p1.next; }        else { lest = l2.val; p2 = p2.next; }        ListNode list = new ListNode(lest);        ListNode node = list;        while(p1 != null || p2 != null) {            if(p1 != null && p2 != null) {                if(p1.val < p2.val) { lest = p1.val; p1 = p1.next; }                else { lest = p2.val; p2 = p2.next; }            }            else if(p1 != null && p2 == null) {                lest = p1.val;                p1 = p1.next;            }            else if(p1 == null && p2 != null) {                lest = p2.val;                p2 = p2.next;            }            node.next = new ListNode(lest);            node = node.next;        }        return list;    }}