CircQueue.java

//circular queue using array
public class CircQueue {
    static class Queue {
        static int arr[];
        static int size;
        static int front = -1;
        static int rear = -1;
 
 
        Queue(int size) {
            this.size = size;
            arr = new int[size];
        }
 
 
        public static boolean isEmpty() {
            return rear == -1 && front == -1;
        }
 
 
        public static boolean isFull() {
            return (rear+1)%size == front;
        }
 
 
        public static void add(int data) {
            if(isFull()) {
                System.out.println("Overflow");
                return;
            }
            //if it's the 1st element
            if(front == -1) {
                front = 0;
            }
 
 
            rear = (rear + 1)%size;
            arr[rear] = data;
        }
 
 
        public static int remove() {
            if(isEmpty()) {
                System.out.println("empty queue");
                return -1;
            }
            int res = arr[front];
 
 
            //if only 1 element is present
            if(front == rear) {
                front = rear = -1;
            } else {
                front = (front+1)%size;
            }
 
 
            return res;
        }
 
 
        public static int peek() {
            if(isEmpty()) {
                System.out.println("empty queue");
                return -1;
            }
           
            return arr[front];
        }
    }
    public static void main(String args[]) {
        Queue q = new Queue(5);
        q.add(1);
        q.add(2);
        q.add(3);
        q.add(4);
        q.add(5);
        System.out.println(q.remove());
        q.add(6);
        System.out.println(q.remove());
        q.add(7);
 
 
        while(!q.isEmpty()) {
            System.out.println(q.remove());
        }
    }
 }