Java 最新环状链表

一、链表的节点类

package com.cache;
public class LinkedListNode {
    public LinkedListNode previous;//前一节点
    public LinkedListNode next;//后一节点
    public Object object;//节点中的数据
  
  

    public LinkedListNode(Object object, LinkedListNode next,
            LinkedListNode previous)
    {
        this.object = object;
        this.next = next;
        this.previous = previous;
    }
  
    public void remove() {//从链表中移去
        previous.next = next;
        next.previous = previous;
    }
  

    public String toString() {
        return object.toString();
    }
}
二、链表类

package com.cache;
import java.util.*;
public class LinkedList {
   
    private LinkedListNode head =
           new LinkedListNode("head", null, null);
 
    public LinkedList() {
        head.next = head.previous = head;//头节点
    }
  
    public LinkedListNode getFirst() ｛//返回头节点后的第一个节点
        LinkedListNode node = head.next;
        if (node == head) {
            return null;
        }
        return node;
    }
  
    public LinkedListNode getLast() {//返回最后一个节点
        LinkedListNode node = head.previous;
        if (node == head) {
            return null;
        }
        return node;
    }
   //将节点加到头节点后
    public LinkedListNode addFirst(LinkedListNode node) {
        node.next = head.next;
        node.previous = head;
        node.previous.next = node;
        node.next.previous = node;
        return node;
    }
  
    public LinkedListNode addFirst(Object object) {
        LinkedListNode node =
          new LinkedListNode(object, head.next, head);
        node.previous.next = node;
        node.next.previous = node;
        return node;
    }
　　//节点添加到链表最后
    public LinkedListNode addLast(Object object) {
        LinkedListNode node =
        new LinkedListNode(object, head, head.previous);
        node.previous.next = node;
        node.next.previous = node;
        return node;
    }

    public void clear() {//清空链表
        //Remove all references in the list.
        LinkedListNode node = getLast();
        while (node != null) {
            node.remove();
            node = getLast();
        }
        //Re-initialize.
        head.next = head.previous = head;
    }
    public String toString() {
        LinkedListNode node = head.next;
        StringBuffer buf = new StringBuffer();
        while (node != head) {
            buf.append(node.toString()).append(", ");
            node = node.next;
        }
        return buf.toString();
    }
}
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