Linear Queue Program Using Array

import java.util.Scanner;

class LinearQueueArray {

    int queue[], size, front, rear;

    public LinearQueueArray(int n) {

          size = n;

          queue = new int[size];

          front = rear = -1;

    }

    public int enqueue(int item) {

        if(front == -1)

              ++front;

          return queue[++rear] = item;

    }

    public int dequeue() {

        return queue[front++];

    }

    public int peek() {

          return queue[front];

    }

    public void display() {

          for(int i=front; i<=rear; i++)

              System.out.printf("%5d", queue[i]);

          System.out.println();

    }

    public boolean isEmpty() {

        return (front == rear + 1 || (front == -1 && rear == -1));

    }

    public boolean isFull() {

        return rear == size - 1;

    }

}

public class LinearQueue {

    public static void main(String[] ar) {

         

          Scanner input = new Scanner(System.in);

         

          System.out.print("\n Enter the length of queue : ");

          int size = input.nextInt();

          LinearQueueArray linearQueueArray = new LinearQueueArray(size);

         

          while(true) {

              System.out.println("\n 1. Enqueue \n 2. Dequeue \n 3. Peek \n 4. display \n Press 0 for exit.");

              System.out.print("\n Enter Your Choice : ");

              int ch = input.nextInt();

              switch(ch) {

                   case 0:                     

                       return;

                   case 1:

                    boolean full = linearQueueArray.isFull();

                    if(full) {

                        System.out.println(" Queue is Full.");

                        break;

                    }

                    System.out.print(" Enter the Element to Enqueue : ");

                    int enqueue = linearQueueArray.enqueue(input.nextInt());

                    System.out.println(" Enqueue Item : " + enqueue);

                       break;

                   case 2:

                    boolean empty = linearQueueArray.isEmpty();

                    if(empty) {

                        System.out.println(" Queue is Empty.");

                        break;

                    }

                    int dequeue = linearQueueArray.dequeue();

                    System.out.println(" Dequeue Item : " + dequeue);

                       break;

                   case 3:

                    boolean emp = linearQueueArray.isEmpty();

                    if(emp) {

                        System.out.println(" Queue is Empty.");

                        break;

                    }

                    int peek = linearQueueArray.peek();

                    System.out.println(" Front Element : " + peek);

                       break;

                   case 4:

                    boolean e = linearQueueArray.isEmpty();

                    if(e) {

                        System.out.println(" Queue is Empty.");

                        break;

                    }

                       linearQueueArray.display();

                       break;

                   default:

                       System.out.println("\n Wrong Choice Entered. ");

              }

          }

    }

}