Prime Number or Not

import java.util.*;
class Prime
{
public static void main(String args[])
{
int n, i, res;
boolean flag=true;
Scanner scan= new Scanner(System.in);
System.out.println("Please Enter a No.");
n=scan.nextInt();
for(i=2;i<=n/2;i++)
{
res=n%i;
if(res==0)
{
flag=false;
break;
}
}
if(flag)
System.out.println(n + " is Prime Number");
else
System.out.println(n + " is not Prime Number");
}
}