Queue : An easy Data Structure in java

import java.io.*;
public class Queue
{
    int Q[];
    int size;
    int front;
    int rear;
    Queue(int cap)
    {
        size = cap;
        Q = new int[size];
        front = 0;
        rear = 0;
    }

    void insert(int v)
    {
        if(rear == size)
        {
            System.out.println("OVERFLOW");
        }
        else
        {
            Q[rear] = v;
            rear = rear + 1;
        }
    }

    int delete()
    {
        if(front == 0 && rear == 0)
        {
            System.out.println("UNDERFLOW");
            return -999;
        }
        else
        {
            int val = Q[front];
            front = front + 1;
            if(front == rear)
            {
                front = 0;
                rear = 0;
            }
            return val;
        }
    }

    void display()
    {
        if(front == 0 && rear == 0)
        {
            System.out.println("The Queue is empty");
        }
        else
        {
            System.out.println("The elements in the queue are : ");
            for(int i=front; i<rear; i++)
            {
                System.out.println(Q[i]);
            }
        }
    }

    public static void main()throws IOException
    {
        System.out.println("************************************ Queue ***********************************");
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter size of Queue:"); int n=Integer.parseInt(br.readLine()); Queue obj=new Queue(n); int ch, gr, t;
        do
        {
            System.out.println("Enter 1 to push element");
            System.out.println("Enter 2 to remove element"); System.out.println("Enter 3 to print list"); System.out.println("Enter 0 to Exit"); System.out.println("Enter your choice"); ch=Integer.parseInt(br.readLine()); switch(ch)
            {
                case 1:
                System.out.println("Enter the value");
                gr=Integer.parseInt(br.readLine());
                obj.insert(gr);
                break;
                case 2:
                gr=obj.delete();
                System.out.println("Obtained Value:"+gr);
                System.out.println("Enter 1 to continue");
                t=Integer.parseInt(br.readLine());
                break;
                case 3:
                obj.display();
                System.out.println("Press 1 to continue");
                t=Integer.parseInt(br.readLine());
                break;
                case 0:
                System.out.println("Thanks For Operating"); break;
                default:
                System.out.println("Re-enter your choice");
            }
        }
        while(ch!=0);
}
}