Java中的双向链表问题

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;
    
    public DoublyLinkedList() {
        this.head = null;
    }
    
    // 在链表头部插入节点
    public void insertAtHead(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            newNode.next = head;
            head.prev = newNode;
            head = newNode;
        }
    }
    
    // 在链表尾部插入节点
    public void insertAtTail(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
            newNode.prev = current;
        }
    }
    
    // 在指定位置插入节点
    public void insertAtPosition(int data, int position) {
        if (position <= 0) {
            insertAtHead(data);
        } else {
            Node newNode = new Node(data);
            Node current = head;
            int currentPosition = 0;
            while (current != null && currentPosition < position) {
                current = current.next;
                currentPosition++;
            }
            if (current != null) {
                newNode.next = current;
                newNode.prev = current.prev;
                current.prev.next = newNode;
                current.prev = newNode;
            } else {
                insertAtTail(data);
            }
        }
    }
    
    // 删除指定位置的节点
    public void deleteAtPosition(int position) {
        if (head == null) {
            return;
        }
        if (position <= 0) {
            head = head.next;
            head.prev = null;
        } else {
            Node current = head;
            int currentPosition = 0;
            while (current != null && currentPosition < position) {
                current = current.next;
                currentPosition++;
            }
            if (current != null) {
                current.prev.next = current.next;
                if (current.next != null) {
                    current.next.prev = current.prev;
                }
            }
        }
    }
    
    // 打印链表
    public void printList() {
        Node current = head;
        while (current != null) {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
}