Program to display whether a number is prime or not in Java

class P17
{
public static void main(String args[])
{
int i,num;


num = 23;
System.out.print(" The Number "+num+" is ");
i=2;
while(i<=num-1)
{
if(num%i==0)
{
System.out.print("Not a prime Number.");
break;
}
i++;
}
if(i==num)
System.out.print("Prime Number.");
}
}