SimpleQueue.java

class Queue {
    int front, rear, size, capacity;
    int array[];

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

    boolean isFull(Queue queue) {
        return (queue.size == queue.capacity);
    }

    boolean isEmpty(Queue queue) {
        return (queue.size == 0);
    }

    void enqueue(int item) {
        if (isFull(this))
            return;
        this.rear = (this.rear + 1) % this.capacity;
        this.array[this.rear] = item;
        this.size = this.size + 1;
    }

    int dequeue() {
        if (isEmpty(this))
            return Integer.MIN_VALUE;
        int item = this.array[this.front];
        this.front = (this.front + 1) % this.capacity;
        this.size = this.size - 1;
        return item;
    }

    int front() {
        if (isEmpty(this))
            return Integer.MIN_VALUE;
        return this.array[this.front];
    }

    int rear() {
        if (isEmpty(this))
            return Integer.MIN_VALUE;
        return this.array[this.rear];
    }

    void printQ(Queue queue) {
        for (int i = this.front; i <= this.rear; i++) {
            System.out.print(this.array[i] + " ");
        }
        // System.out.println("Sahil");
    }
}

public class SimpleQueue {
    public static void main(String[] args) {
        Queue q = new Queue(100);
        q.enqueue(1);
        q.enqueue(2);
        q.enqueue(3);
        q.enqueue(4);
        q.enqueue(5);
        q.printQ(q);
        System.out.println();
        q.dequeue();
        q.printQ(q);
    }
}