boolean (int bits) { if ((bits & 1) == 0 || bits % 3 == 0) { return false; } int sqrt = (int)Math.sqrt(bits); for (int i = 6; i <= sqrt; i += 6) { if (bits % (i - 1) == 0 || bits % (i + 1) == 0) { return false; } } return true; }