Queue Implementation

REF.

import java.util.*;

// Class for queue
public class Queue {
    private int[] arr; // array to store queue elements
    private int front; // front points to front element in the queue
    private int rear; // rear points to last element in the queue
    private int capacity; // maximum capacity of the queue
    private int count; // current size of the queue

    // Constructor to initialize queue
    Queue(int size) {
        arr = new int[size];
        capacity = size;
        front = 0;
        rear = 0;
        count = 0;
    }

    // Utility function to remove front element from the queue
    public void poll() {
        // check for queue underflow
        if (isEmpty()) {
            System.out.println("UnderFlow\nProgram Terminated");
            System.exit(1);
        }

        System.out.println("Removing " + arr[front]);

        front = (front + 1) % capacity;
        count--;
    }

    // Utility function to add an item to the queue
    public void offer(int item) {
        // check for queue overflow
        if (isFull()) {
            System.out.println("OverFlow\nProgram Terminated");
            System.exit(1);
        }

        System.out.println("Inserting " + item);

        arr[rear] = item;
        rear = (rear + 1) % capacity; 
        count++;
    }

    // Utility function to return front element in the queue
    public int peek() {
        if (isEmpty()) {
            System.out.println("UnderFlow\nProgram Terminated");
            System.exit(1);
        }
        return arr[front];
    }

    // Utility function to return the size of the queue
    public int size() {
        return count;
    }

    // Utility function to check if the queue is empty or not
    public Boolean isEmpty() {
        return (size() == 0);
    }

    // Utility function to check if the queue is full or not
    public Boolean isFull() {
        return (size() == capacity);
    }

}