Check whether a number is Prime or not

PrimeNum.java

import java.util.Scanner;
/**
 *
 * @author tech gokul
 */
public class PrimeNum {

    
    public static void main(String[] args) {
        
        int num, i = 2;
        boolean flag = false;
    System.out.println("Enter the number to check the number is prime or not: ");
        Scanner in= new Scanner(System.in);
        num= in.nextInt();


        while(i <= num/2)
        {
            // condition for nonprime number
            if(num % i == 0)
            {
                flag = true;
                break;
            }

            ++i;
        }

        if (!flag)
            System.out.println(num + " is a prime number.");
        else
            System.out.println(num + " is not a prime number.");
    }
    
}