CustomQueue.java

package com.sarvesh.javabasics;

public class CustomQueue {
 int[] arr;
 int front; 
 int rear; 

 public CustomQueue(int size) {
 arr = new int[size];
 front = 0;
 rear = 0;
 }

 public void enqueue(int x) {
 if (rear == arr.length) {
 System.out.println("The line is full! Cannot add " + x);
 return;
 } 
 arr[rear] = x;
 rear++; 
 }

 public int dequeue() {
 if (front == rear) {
 System.out.println("The line is empty!");
 return -1;
 }
 int servedPerson = arr[front];
 front++; 
 return servedPerson;
 }

 public int peek() {
 if (front == rear) return -1;
 return arr[front];
 }

 public static void main(String[] args) {
 CustomQueue engine = new CustomQueue(5);
 
 engine.enqueue(10); 
 engine.enqueue(20); 
 engine.enqueue(30); 
 
 System.out.println("Served: " + engine.dequeue()); 
 System.out.println("Next up: " + engine.peek()); 
 }
}