带头结点的循环链表表示队列，并且只设一个指针指向队尾元素站点，不设头指针。试编写相应的置空队、判队空、入队和出队的java 算法。

public class QueueWithCircularLinkedList {
    private Node rear;  // 指向队尾元素的指针

    public QueueWithCircularLinkedList() {
        rear = null;  // 初始化为空队列
    }

    // 置空队
    public void clear() {
        rear = null;
    }

    // 判队空
    public boolean isEmpty() {
        return rear == null;
    }

    // 入队
    public void enqueue(int value) {
        Node newNode = new Node(value);
        if (rear == null) {  // 队列为空
            rear = newNode;
            newNode.next = newNode;  // 环形链表
        } else {
            newNode.next = rear.next;
            rear.next = newNode;
            rear = newNode;
        }
    }

    // 出队
    public int dequeue() throws Exception {
        if (isEmpty()) {
            throw new Exception("队列为空，不能出队");
        }
        int value;
        if (rear.next == rear) {  // 队列只有一个元素
            value = rear.data;
            rear = null;
        } else {
            Node front = rear.next;
            value = front.data;
            rear.next = front.next;
            front.next = null;
        }
        return value;
    }

    // 链表节点类
    private class Node {
        int data;
        Node next;

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