无头双向链表的相关操作（Java实现）

package singleList;
//无头双向链表
public class DoubleLinkedList {

    class Node{
        private int data;
        private Node next;
        private Node prev;
        public Node(int data){
            this.data = data;
            this.next = null;
            this.prev = null;
        }
    }

    private Node head;
    private Node last;
    public DoubleLinkedList(){
        this.head = null;
    }

    //1.头插,head变，last不变
    public void addFirst(int data){
        Node node = new Node(data);
        if(head == null){
            this.head = node;
            this.last = node;
        }else {
            node.next = this.head;
            this.head.prev = node;
            this.head = node;
        }
    }
    //2.尾插，头不变，last变
    public void addLast(int data){
        Node node = new Node(data);
        if(this.last == null){
            this.last = node;
            this.head = node;
        }else {
            this.last.next = node;
            node.prev = this.last;
            this.last = node;
        }
    }
    //3.获取链表长度
    public int getLength(){
        Node cur = this.head;
        int len = 0;
        while(cur != null){
            len++;
            cur = cur.next;
        }
        return len;
    }
    //4.在指定索引位置插入数据，只能在[0,lenth]区间插入
    //如要在: 1->2->3->4->null 的index=2位置插入data=5，则为：1->2->5->3->4->null
    public boolean addIndex(int index, int data){
        if(index < 0 || index > this.getLength()){
            System.out.println("插入位置不合法！");
            return false;
        }
        if(index == 0){
            addFirst(data);
            return true;
        }
        if(index == this.getLength()) {
            addLast(data);
            return true;
        }
        Node node = new Node(data);
        Node cur = this.head;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        cur.prev.next = node;
        node.next = cur;
        node.prev = cur.prev;
        cur.prev = node;
        return true;
    }
    //5.是否包含key
    public boolean contains(int key){
        Node cur = this.head;
        while(cur != null){
            if(cur.data == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //6.移除链表中等于key的第一个元素节点
    public boolean remove(int key){
        if(this.head == null){
            return false;
        }
        // 1->2->4
        Node cur = this.head;
        while(cur != null){
            if(cur.data == key){
                if(cur == this.head){
                    //是头节点
                    if(cur.next == null){
                        //只有一个元素
                        this.head = this.last = null;
                    }else {
                        cur.next.prev = null;
                        this.head = cur.next;
                    }
                    return true;
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null){
                        //是尾节点
                        this.last = cur.prev;
                    }else {
                        cur.next.prev = cur.prev;
                        return true;
                    }
                }
                return true;
            }
            cur = cur.next;

        }
        return false;
    }
    //7.移除链表中所有等于key的节点
    public void removeAllKey(int key){
        if(this.head == null){
            return ;
        }
        Node cur = this.head;
        while (cur != null){
            if(cur.data == key){
                //移除头节点
                if(cur == this.head){
                    if(cur.next == null){
                        //只有一个元素
                        this.head = this.last = null;
                        return ;
                    }else {
                        cur.next.prev = null;
                        this.head = cur.next;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null){
                        this.last = cur.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }
    //8.清除链表
    public void clear(){
        while(this.head != null){
            Node cur = this.head.next;
            this.head.next = null;
            this.head.prev = null;
            this.head = cur;
        }
        this.last = null;
    }
    //9.打印双向链表
    public void display(){
        if(this.head == null){
            System.out.println("链表为空！");
        }else {
            Node cur = this.head;
            while(cur != null){
                System.out.print(cur.data);
                System.out.print("->");
                cur = cur.next;
            }
            System.out.println();
        }
    }

    public static void main(String[] args) {
        DoubleLinkedList linkedList = new DoubleLinkedList();

        linkedList.addLast(1);
        linkedList.addLast(2);
        linkedList.addLast(3);
        linkedList.addLast(3);
        linkedList.addLast(4);
        linkedList.addLast(5);
        linkedList.addLast(5);
        linkedList.addLast(6);
        linkedList.clear();
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }
}