Java Program for Queue Simulation

Program

import java.io.*;
import java.util.*;
class queue {
    private final int size = 5;
    private int front, rear;
    private int que[];
    queue() {
        front = 0;
        rear = -1;
        que = new int[size];
    }
    void insert(int item) {
        if (rear == size - 1) {
            System.out.println("Queue full");
            return;
        } else {
            que[++rear] = item;
            System.out.println("Element inserted is:\t" + que[rear]);
            return;
        }
    }
    void del() {
        if (front > rear) {
            System.out.println("Queue Empty");
            return;
        } else {
            System.out.println("Element deleted is:\t" + que[front]);
            front++;
        }
        if (front > rear) {
            front = 0;
            rear = -1;
        }
    }
    void display() {
        if (front > rear) {
            System.out.println("Queue Empty");
            return;
        } else {
            System.out.println("Contents of Queue:");
            for (int i = front; i <= rear; i++)
                System.out.println(que[i]);
            return;
        }
    }
}
public class QueueSimulation {
    public static void main(String[] args) {
        queue q = new queue();
        int choice;
        Scanner sc = new Scanner(System.in);
        System.out.println("QUEUES");
        while (true) {
            System.out.println("1. Insert\n2. Delete\n3. Display\n4. Exit");
            System.out.println("Enter choice");
            choice = sc.nextInt();
            switch (choice) {
            case 1:
                System.out.println("Enter the item to insert");
                int item = sc.nextInt();
                q.insert(item);
                break;
            case 2:
                q.del();
                break;
            case 3:
                q.display();
                break;
            case 4:
                sc.close();
                System.exit(0);
                break;
            default:
                System.out.println("Invalid choice");
            }
        }
    }
}

Output

QUEUES
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
10
Element inserted is:    10
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
20
Element inserted is:    20
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
30
Element inserted is:    30
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
40
Element inserted is:    40
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
50
Element inserted is:    50
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
1
Enter the item to insert
60
Queue full
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Element deleted is:     10
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Element deleted is:     20
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Element deleted is:     30
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
3
Contents of Queue:
40
50
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Element deleted is:     40
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Element deleted is:     50
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
2
Queue Empty
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
3
Queue Empty
1. Insert
2. Delete
3. Display
4. Exit
Enter choice
4