CircularQueue.java

package queque.dsa.lab;

public class CircularQueue {
    private int capacity;
    private int[] queueArray;
    private int front;
    private int rear;
    private int size;

    // Constructor to initialize the queue
    public CircularQueue(int capacity) {
        this.capacity = capacity;
        queueArray = new int[capacity];
        front = -1;
        rear = -1;
        size = 0;
    }

    // Method to check if the queue is empty
    public boolean isEmpty() {
        return size == 0;
    }

    // Method to check if the queue is full
    public boolean isFull() {
        return size == capacity;
    }

    // Method to add an element to the rear of the queue
    public void enqueue(int item) {
        if (isFull()) {
            System.out.println("Queue is full. Cannot enqueue.");
            return;
        }
        if (front == -1) {
            front = 0;
        }
        rear = (rear + 1) % capacity;
        queueArray[rear] = item;
        size++;
        System.out.println(item + " enqueued to the queue");
    }

    // Method to remove an element from the front of the queue
    public int dequeue() {
        if (isEmpty()) {
            System.out.println("Queue is empty. Cannot dequeue.");
            return -1;
        }
        int dequeuedItem = queueArray[front];
        if (front == rear) {
            front = -1;
            rear = -1;
        } else {
            front = (front + 1) % capacity;
        }
        size--;
        return dequeuedItem;
    }

    // Method to get the front element of the queue without removing it
    public int peek() {
        if (isEmpty()) {
            System.out.println("Queue is empty.");
            return -1;
        }
        return queueArray[front];
    }

    // Method to get the size of the queue
    public int size() {
        return size;
    }

    // Method to display the elements of the queue
    public void display() {
        if (isEmpty()) {
            System.out.println("Queue is empty.");
            return;
        }
        System.out.print("Queue: ");
        int i = front;
        do {
            System.out.print(queueArray[i] + " ");
            i = (i + 1) % capacity;
        } while (i != (rear + 1) % capacity);
        System.out.println();
    }

    public static void main(String[] args) {
        CircularQueue queue = new CircularQueue(5);

        queue.enqueue(10);
        queue.enqueue(20);
        queue.enqueue(30);
        queue.enqueue(40);
        queue.enqueue(50);
        queue.enqueue(60); // Queue is full, this will not be enqueued

        queue.display(); // Display the queue

        System.out.println("Dequeued element: " + queue.dequeue());
        System.out.println("Front element: " + queue.peek());
        System.out.println("Queue size: " + queue.size());

        queue.display(); // Display the queue after dequeue
    }
}