反转一个单向链表。

public class ReversingLinkedList {

    static class Node {
        int val;
        Node next;

        public Node(int val) {
            this.val = val;
        }

        public boolean hasNext() {
            return next != null;
        }
    }

    public static void main(String[] args) {
        //构造
        Node head = null;
        Node shift = null;
        for (int i = 1; i <= 10; i++) {
            Node node = new Node(i);
            if (head == null) {
                head = node;
                shift = node;
            } else {
                shift.next = node;
                shift = node;
            }
        }
        print(head);

        //反转
        Node tail = null;
        while (head.hasNext()) {
            //a
            Node tmp = head;
            //b
            head = head.next;

            //c
            tmp.next = tail;
            //d
            tail = tmp;
        }

        head.next = tail;
        tail = head;
        print(tail);
    }

    static void print(Node node) {
        while (node.hasNext()) {
            System.out.print(node.val + " -> ");
            node = node.next;
        }
        System.out.println(node.val);
    }
}