A Queue is a linear data structure that follows the FIFO (First In, First Out) principle. The first element added to the queue is the first one to be removed.

Real-World Analogy

Imagine a line of people waiting at a movie ticket counter. The person who arrives first gets served first, and new people join at the end of the line (Rear). Core Operations

• Enqueue: Add an element to the rear of the queue.
• Dequeue: Remove and return the front element.
• Front/Peek: View the front element without removing it.
• Rear: View the last element.

Java Implementation (Array-Based)

Below is the Java code for a simple Queue .

class Queue {
    private int maxSize;
    private int[] queueArray;
    private int front;
    private int rear;
    private int currentSize;

    public Queue(int size) {
        this.maxSize = size;
        this.queueArray = new int[maxSize];
        this.front = 0;
        this.rear = -1;
        this.currentSize = 0;
    }

    // Enqueue: Add to rear
    public void enqueue(int value) {
        if (isFull()) {
            System.out.println("Queue is full! Cannot enqueue " + value);
            return;
        }
        rear = (rear + 1) % maxSize; // Handles wrapping for array
        queueArray[rear] = value;
        currentSize++;
        System.out.println("Enqueued: " + value);
    }

    // Dequeue: Remove from front
    public int dequeue() {
        if (isEmpty()) {
            System.out.println("Queue is empty! Cannot dequeue");
            return -1;
        }
        int value = queueArray[front];
        front = (front + 1) % maxSize;
        currentSize--;
        System.out.println("Dequeued: " + value);
        return value;
    }

    public int peek() {
        if (isEmpty()) {
            System.out.println("Queue is empty!");
            return -1;
        }
        return queueArray[front];
    }

    public boolean isEmpty() {
        return currentSize == 0;
    }

    public boolean isFull() {
        return currentSize == maxSize;
    }
}