Circular Queue using Linked List in Java

class Node {
    int data;
    Node next;

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

public class CircularQueueLinkedList {

    private Node front;
    private Node rear;

    public CircularQueueLinkedList() {
        front = rear = null;
    }

    // Check if queue is empty
    public boolean isEmpty() {
        return front == null;
    }

    // Enqueue operation
    public void enqueue(int value) {

        Node newNode = new Node(value);

        if (isEmpty()) {
            front = rear = newNode;
            rear.next = front; // circular link
        } else {
            rear.next = newNode;
            rear = newNode;
            rear.next = front;
        }

        System.out.println(value + " inserted");
    }

    // Dequeue operation
    public int dequeue() {

        if (isEmpty()) {
            System.out.println("Queue is empty (Underflow)");
            return -1;
        }

        int value;

        // If only one element
        if (front == rear) {
            value = front.data;
            front = rear = null;
        } else {
            value = front.data;
            front = front.next;
            rear.next = front;
        }

        return value;
    }

    // Peek operation
    public int peek() {
        if (isEmpty()) {
            System.out.println("Queue is empty");
            return -1;
        }
        return front.data;
    }

    // Display queue
    public void display() {

        if (isEmpty()) {
            System.out.println("Queue is empty");
            return;
        }

        System.out.print("Circular Queue: ");

        Node temp = front;
        do {
            System.out.print(temp.data + " ");
            temp = temp.next;
        } while (temp != front);

        System.out.println();
    }

    // Main method
    public static void main(String[] args) {

        CircularQueueLinkedList queue = new CircularQueueLinkedList();

        queue.enqueue(10);
        queue.enqueue(20);
        queue.enqueue(30);

        queue.display();

        System.out.println("Removed: " + queue.dequeue());
        System.out.println("Removed: " + queue.dequeue());

        queue.display();

        queue.enqueue(40);
        queue.enqueue(50);

        queue.display();

        System.out.println("Front element: " + queue.peek());

        System.out.println("Removed: " + queue.dequeue());
        System.out.println("Removed: " + queue.dequeue());
        System.out.println("Removed: " + queue.dequeue());

        queue.display();  // underflow case
    }
}