java实现双向循环链表（附完整源码）

请参考以下代码：

public class DoublyLinkedList<T> {
    private Node<T> head;
    private Node<T> tail;

    private static class Node<T> {
        private T value;
        private Node<T> prev;
        private Node<T> next;

        public Node(T value) {
            this.value = value;
        }
    }

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

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

    public void addFirst(T value) {
        Node<T> newNode = new Node<>(value);
        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 addLast(T value) {
        Node<T> newNode = new Node<>(value);
        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;
            tail = newNode;
        }
    }

    public void removeFirst() {
        if (!isEmpty()) {
            if (head == tail) {
                head = null;
                tail = null;
            } else {
                head = head.next;
                head.prev = tail;
                tail.next = head;
            }
        }
    }

    public void removeLast() {
        if (!isEmpty()) {
            if (head == tail) {
                head = null;
                tail = null;
            } else {
                tail = tail.prev;
                tail.next = head;
                head.prev = tail;
            }
        }
    }

    public void print() {
        if (!isEmpty()) {
            Node<T> current = head;
            do {
                System.out.print(current.value + " ");
                current = current.next;
            } while (current != head);
            System.out.println();
        }
    }
}

使用示例：

public class Main {
    public static void main(String[] args) {
        DoublyLinkedList<Integer> list = new DoublyLinkedList<>();
        list.addFirst(10);
        list.addLast(20);
        list.addFirst(5);
        list.addLast(30);
        list.print();  // 5 10 20 30
        list.removeFirst();
        list.removeLast();
        list.print();  // 10 20
    }
}