反转链表的ACM

class ListNode{
    int val;
    ListNode next=null;
    ListNode(int val){
        this.val = val;
    }
}

//包括主函数建立链表和关键代码两部分
public class Main{
    public static void main(String[] args) {
        ListNode node = new ListNode(0);
        ListNode head = node ;
        for (int i = 1; i < 5; i++) {
            node.next = new ListNode(i);
            node = node.next;
        }
        //0 1 2 3 4
        ListNode listNode = power(head);
        while(listNode!=null){
            System.out.println(listNode.val);
            listNode=listNode.next;
        }
    }
    static ListNode power(ListNode head){
        ListNode pre=null;
        while(head!=null){
            ListNode temp=head.next;
            head.next=pre;
            pre=head;
            head=temp;
        }
        return  pre;
    }

}