java实现环形链表带哨兵

双向环形链表带哨兵，这时哨兵既作为头，也作为尾。

package com.tfq.arithmetic.linkedlist;

import java.util.Iterator;

/**
 * @author: fqtang
 * @date: 2024/05/22/8:40
 * @description: 环形链表
 */
public class DoublyLinkedListSentinel implements Iterable<Integer> {

	private static class Node {
		Node prev;//上一个节点指针
		int value;//值
		Node next;//下一个节点指针

		public Node(Node prev, int value, Node next) {
			this.prev = prev;
			this.next = next;
			this.value = value;
		}
	}

	/**
	 * 哨兵对象
	 */
	private Node sentinel = new Node(null, -1, null);

	public DoublyLinkedListSentinel() {
		sentinel.prev = sentinel;
		sentinel.next = sentinel;
	}

	/**
	 * 添加到第一个
	 *
	 * @param value -待添加值
	 */
	public void addFirst(int value) {
		Node a = sentinel;
		Node b = sentinel.next;
		Node added