21. Merge Two Sorted Lists

import jdk.management.resource.internal.inst.AbstractPlainDatagramSocketImplRMHooks;public class Solution {    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {        ListNode listNode = new ListNode(0);        ListNode tmp = listNode;        while (true) {            if(l1==null) {                if(l2==null) return tmp.next;                listNode.next = l2;                return tmp.next;            } else {                if(l2 ==null) {                    listNode.next = l1;                    return tmp.next;                } else {                    if(l1.val >= l2.val) {                        listNode.next = l2;                        listNode = listNode.next;                        l2 = l2.next;                    } else {                        listNode.next = l1;                        listNode = listNode.next;                        l1 = l1.next;                    }                }            }        }    }//    public static void main(String[] args) {//        ListNode node1 = new ListNode(1);//        ListNode node3 = new ListNode(10);//        node1.next = node3;//        ListNode node2 = new ListNode(2);//        ListNode node4 = new ListNode(4);//        node2.next = node4;//        ListNode node = (new Solution()).mergeTwoLists(node1, node2);//        while (node != null) {//            System.out.print(node.val + " ");//            node = node.next;//        }//    }}class ListNode {     int val;     ListNode next;     ListNode(int x) { val = x; } }