java实现双向链表

利用java实现 带有头节点 尾节点的双向链表，以及基本的方法实现

/**
 * Created by pandap on 2017/8/4.
 * 双向链表的java实现
 */
public class MyList {
    /*
    内部节点类
     */
    private class Node{
        public Node pre;
        public Node next;
        public T data;

        public Node(){
            this.data = null;
            this.next = null;
            this.pre = null;
        }
        public Node(T data,Node pre, Node next){
            this.data = data;
            this.pre = pre;
            this.next = next;
        }
    }
    //链表的属性 大小 头节点 尾节点
    private int size;
    private Node header;
    private Node tail;

    //初始化链表
    public MyList(){
        this.size = 0;
        header = new Node(null,null,null);
        tail = new Node(null,header,null);
        header.next = tail;
        if(header == null){
            System.out.println("header is null");
        }
        if(tail == null){
            System.out.println("tail isi null");
        }
    }
//添加元素
    public void add(T item){
        Node newNode = new Node(item,null,null);
        tail.pre.next = newNode;
        newNode.pre = tail.pre;
        newNode.next = tail;
        tail.pre = newNode;
        size++;
    }
//判空
    public boolean isEmpty(){
        return size == 0;
    }

    public int size(){
        return size;
    }
//获取某个节点
    public T get(int idx){
        if(idx >= size || idx < 0){
            throw new IndexOutOfBoundsException();
        }
        Node current = header;
        for(int i=0; i<=idx; i++){
            current = current.next;
        }
        return (T)current.data;
    }
//输出链表
    public void print(){
        Node current = header.next;
        while(current.next != null){
            System.out.println(current.data.toString());
            current = current.next;
        }
    }
//    测试
    public static void main(String[] args) {
        MyList strs = new MyList();
        strs.add("first");
        strs.add("second");
        strs.add("three");
        System.out.println("size :" + strs.size);
        strs.print();
        System.out.println(strs.get(0));
    }

}

测试结果