哑节点合并两个排序链表

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode Merge(ListNode list1,ListNode list2) {

        ListNode dummy = new ListNode(-1);
        ListNode temp = dummy;
        while(list1 != null && list2 != null){
            if(list1.val < list2.val){
                temp.next = list1;
                list1 = list1.next;
            }else{
                temp.next = list2;
                list2 = list2.next;
            }
            temp = temp.next;
        }
        temp.next = (list1 != null) ? list1 : list2;
        return dummy.next;
    }
}