public class CNode<T> {

    public CNode prev;

    public CNode next;

    public T data;

    public CNode() {

    }

    public CNode(T data) {

        this.data = data;

    }

}

public class DoubleLinkNode<T> {

    /**

     * 初始化

     *

     * @param head

     */

    public void init(CNode head) {

        head.prev = head;

        head.next = head;

    }

    /**

     * 插入

     *

     * @param head：插入对应链表

     * @param index：插入的位置

     * @param element:    对应位置插入的元素

     */

    public void insert(CNode head, int index, T element) {

        CNode temp = head;

        CNode<T> newnode = new CNode<>(element);

        int j = -1;

        while (temp.next != head && j < index - 1) {

            temp = temp.next;

            j++;

        }

        if (j != index - 1) {

            System.out.println("插入的下标有问题");

            return;

        }

        newnode.next = temp.next;//---->

        temp.next.prev = newnode;//<----

        newnode.prev = temp;//---->

        temp.next = newnode;//<---

    }

    /**

     * 删除

     * @param head：所要删除的链表

     * @param index ：删除的元素下标

     */

    public void delete(CNode head, int index) {

        CNode temp = head;

        int j = -1;

        if (temp.next == head) {

            System.out.println("链表为空，没有元素可删除");

            return;

        }

        while (temp.next.next != head && j < index - 1) {

            temp = temp.next;

            j++;

        }

        if (j != index - 1) {

            System.out.println("删除元素位置下标出错");

            return;

        }

        temp.next = temp.next.next;

        temp = temp.next.next.prev;

    }

    public void indexGetElement(CNode head,int index) {

        CNode temp = head;

        int j = -1;

        if (temp.next == head){

            System.out.println("为空，无法获取你要的值");

            return;

        }

        while (temp.next != head && j< index){

            temp = temp.next;

            j++;

        }

        if (j != index){

            System.out.println("您给的下标有问题");

            return;

        }

        System.out.println("您要获取的值："+temp.data);

    }

    /**

     * 求当前元素个数

     *

     * @param head

     */

    public void getLength(CNode head) {

        CNode temp = head;

        int length = 0;

        if (temp.next == head) {

            System.out.println("链表为空，长度为0");

            return;

        }

        while (temp.next != head) {

            temp = temp.next;

            length++;

        }

        System.out.println("长度为： " + length);

    }

    /**

     * 打印

     *

     * @param head

     */

    public void print(CNode head) {

        CNode temp = head;

        if (temp.next == head) {

            System.out.println("链表为空，没有可打印元素");

            return;

        }

        while (temp.next != head) {

            temp = temp.next;

            System.out.print(temp.data + " ");

        }

        System.out.println();

    }

    public static void main(String[] args) {

        CNode<Integer> cNode = new CNode<>();

        DoubleLinkNode doubleLinkNode = new DoubleLinkNode();

        doubleLinkNode.init(cNode);

        doubleLinkNode.indexGetElement(cNode,0);

        doubleLinkNode.insert(cNode, 0, 8);

        doubleLinkNode.insert(cNode, 0, 7);

        doubleLinkNode.getLength(cNode);

        doubleLinkNode.print(cNode);

        for (int i = 0; i < 5; i++) {

            doubleLinkNode.insert(cNode, i, i);

        }

        doubleLinkNode.print(cNode);

        doubleLinkNode.getLength(cNode);

        doubleLinkNode.delete(cNode,6);

        doubleLinkNode.print(cNode);

        doubleLinkNode.getLength(cNode);

        doubleLinkNode.indexGetElement(cNode,5);

    }

}

为空，无法获取你要的值

长度为： 2

7 8

0 1 2 3 4 7 8

长度为： 7

0 1 2 3 4 7

长度为： 6

您要获取的值：7