public class DoublyLinkedList {

    Node head; // head 節(jié)點(diǎn)

    //Node表示的是Linked list中的節(jié)點(diǎn)，包含一個(gè)data數(shù)據(jù)，上一個(gè)節(jié)點(diǎn)和下一個(gè)節(jié)點(diǎn)的引用
    class Node {
        int data;
        Node next;
        Node prev;
        //Node的構(gòu)造函數(shù)
        Node(int d) {
            data = d;
        }
    }
}

    //插入到linkedList的頭部
    public void push(int newData) {
        //構(gòu)建要插入的節(jié)點(diǎn)
        Node newNode = new Node(newData);
        //新節(jié)點(diǎn)的next指向現(xiàn)在的head節(jié)點(diǎn)
        //新節(jié)點(diǎn)的prev指向null
        newNode.next = head;
        newNode.prev = null;

        if (head != null)
            head.prev = newNode;

        //現(xiàn)有的head節(jié)點(diǎn)指向新的節(jié)點(diǎn)
        head = newNode;
    }

 //新節(jié)點(diǎn)插入到list最后面
    public void append(int newData) {
        //創(chuàng)建新節(jié)點(diǎn)
        Node newNode = new Node(newData);
        //如果list是空，則新節(jié)點(diǎn)作為head節(jié)點(diǎn)
        if (head == null) {
            newNode.prev = null;
            head = newNode;
            return;
        }

        newNode.next = null;
        //找到最后一個(gè)節(jié)點(diǎn)
        Node last = head;
        while (last.next != null) {
            last = last.next;
        }
        //插入
        last.next = newNode;
        newNode.prev = last;
        return;
    }

   //插入在第幾個(gè)元素之后
    public void insertAfter(int index, int newData) {
        Node prevNode = head;
        for (int i = 1; i < index; i++) {
            if (prevNode == null) {
                System.out.println("輸入的index有誤，請(qǐng)重新輸入");
                return;
            }
            prevNode = prevNode.next;
        }
        //創(chuàng)建新的節(jié)點(diǎn)
        Node newNode = new Node(newData);
        //新節(jié)點(diǎn)的next指向prevNode的下一個(gè)節(jié)點(diǎn)
        newNode.next = prevNode.next;
        //將新節(jié)點(diǎn)插入在prevNode之后
        prevNode.next = newNode;
        //將新節(jié)點(diǎn)的prev指向prevNode
        newNode.prev = prevNode;

        //newNode的下一個(gè)節(jié)點(diǎn)的prev指向newNode
        if (newNode.next != null)
            newNode.next.prev = newNode;
    }

 //刪除特定位置的節(jié)點(diǎn)
    void deleteNode(int index)
    {
        // 如果是空的，直接返回
        if (head == null)
            return;

        // head節(jié)點(diǎn)
        Node temp = head;

        // 如果是刪除head節(jié)點(diǎn)
        if (index == 1)
        {
            head = temp.next;
            return;
        }

        // 找到要?jiǎng)h除節(jié)點(diǎn)的前一個(gè)節(jié)點(diǎn)
        for (int i=1; temp!=null && i<index-1; i++)
            temp = temp.next;

        // 如果超出范圍
        if (temp == null || temp.next == null)
            return;

        // temp->next 是要?jiǎng)h除的節(jié)點(diǎn)，刪除節(jié)點(diǎn)
        Node next = temp.next.next;
        temp.next = next;
        Node prev = temp.next.prev;
        prev.prev = prev;
    }