Java program to find wehter number is prime or not?

class PrimeNo{
 public static void main(String args[]){
  int num = Integer.parseInt(args[0]);
  int flag=0;
  for(int i=2;i<num;i++){
   if(num%i==0)
   {
    System.out.println(num+" is not a Prime Number");
    flag = 1;
    break;
   }
  }
  if(flag==0)
   System.out.println(num+" is a Prime Number");
 }
}