QueueB.java

//queue using array
public class QueueB {
    static class Queue {
        static int arr[];
        static int size;
        static int rear;
 
 
        Queue(int size) {
            this.size = size;
            arr = new int[size];
            rear = -1;
        }
 
 
        public static boolean isEmpty() {
            return rear == -1;
        }
 
 
        public static boolean isFull() {
            return rear == size-1;
        }
 
 
        public static void add(int data) {
            if(isFull()) {
                System.out.println("Overflow");
                return;
            }
 
 
            arr[++rear] = data;
        }
 
 
        //O(n)
        public static int remove() {
            if(isEmpty()) {
                System.out.println("empty queue");
                return -1;
            }
            int front = arr[0];
            for(int i=0; i<rear; i++) {
                arr[i] = arr[i+1];
            }
          rear--;	
            return front;
        }
 
 
        public static int peek() {
            if(isEmpty()) {
                System.out.println("empty queue");
                return -1;
            }
           
            return arr[0];
        }
    }
    public static void main(String args[]) {
        Queue q = new Queue(5);
        q.add(1);
        q.add(2);
        q.add(3);
        System.out.println(q.remove());
        System.out.println(q.peek());
    }
 }