双向循环链表java

以下是一个双向循环链表的Java实现示例：

public class DoublyLinkedList {
    private Node head;
    private Node tail;

    private class Node {
        int val;
        Node prev;
        Node next;

        public Node(int val) {
            this.val = val;
        }
    }

    public DoublyLinkedList() {
        head = null;
        tail = null;
    }

    public boolean isEmpty() {
        return head == null;
    }

    public void insertAtHead(int val) {
        Node newNode = new Node(val);
        if (isEmpty()) {
            head = newNode;
            tail = newNode;
            newNode.next = newNode;
            newNode.prev = newNode;
        } else {
            newNode.next = head;
            newNode.prev = tail;
            head.prev = newNode;
            tail.next = newNode;
            head = newNode;
        }
    }

    public void insertAtTail(int val) {
        Node newNode = new Node(val);
        if (isEmpty()) {
            head = newNode;
            tail = newNode;
            newNode.next = newNode;
            newNode.prev = newNode;
        } else {
            newNode.next = head;
            newNode.prev = tail;
            tail.next = newNode;
            head.prev = newNode;
            tail = newNode;
        }
    }

    public void display() {
        Node cur = head;
        if (cur == null) {
            System.out.println("双向链表为空");
            return;
        }
        do {
            System.out.print(cur.val + " ");
            cur = cur.next;
        } while (cur != head);
        System.out.println();
    }
}

使用示例：

DoublyLinkedList list = new DoublyLinkedList();
list.insertAtHead(3);
list.insertAtHead(2);
list.insertAtHead(1);
list.insertAtTail(4);
list.insertAtTail(5);
list.display(); // 输出：1 2 3 4 5