如何在java中实现循环双向链表添加方法

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

class DoublyLinkedList {
    Node head;
    Node tail;
    
    public DoublyLinkedList() {
        this.head = null;
        this.tail = null;
    }
}

class DoublyLinkedList {
    // ...

    public void add(int data) {
        Node newNode = new Node(data);
        
        if (head == null) {
            head = newNode;
            tail = newNode;
        } else {
            tail.next = newNode;
            newNode.prev = tail;
            tail = newNode;
        }
        
        tail.next = head; // 将尾节点的next指针指向头节点，形成循环
        head.prev = tail; // 将头节点的prev指针指向尾节点，形成循环
    }
    
    // ...
}