Queue_byCircularArray.java

public class Queue_byCircularArray {
     static class Queue{
        static int arr[];
        static int size;
        static int rear = -1;
        static int front = -1;
        Queue(int n){
            arr = new int[n];
            this.size = n;
        }
        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("full queue");
                return;
            }
            // for adding very first 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 result = arr[front];
            // single element condition
            if(rear == front) {rear=front=-1;}
            else {front = (front+1)%size;}

            return result;
        }
        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(0);
        q.add(1);
        q.add(2);
        q.add(3);
        //q.remove();
        while(!q.isEmpty()){
            System.out.println(q.peek());
            q.remove();
        }
    }
}