双向链表

package hash_map.link;



//双向链表  
/**
 * 每个节点由3部分组成：指向前一个节点的引用，数据区，指向后一个节点的引用
 *
 */
public class TwoWay {
    
    Node first;
    Node last;
    
    class Node{
        long data;
        Node pre;
        Node next;
        public Node(long data) {
            this.data = data;
        }
        
    }
    
    //向头结点插入元素
    public void insertFirst(long data){
        Node node = new Node(data);
        if (first == null) {
            first = node;
        }else {
            first.pre = node;
            node.next = first;
        }
        last = node;
    }
    
    
    //向尾节点插入元素
    public void insertLast(long data){
        Node node = new Node(data);
        if (first == null) {
            first = node;
        }else {
            last.next = node;
            node.pre = last;
        }
        
        last = node;
    }
    
    public static void main(String[] args) {
        
    }

}