public static final boolean isPrimaryNum(int num) { if(num <= 1) { return false; } if(num == 2 || num == 3) { return true; } int sqrt = (int)Math.sqrt(num); if(num % 2 == 0) return false; for(int i = 3; i <= sqrt; i += 2) { if(num % i == 0) return false; } return true; }