HackerRank-Solutions/Java/BigNumber/Java Primality Test/Solution.java

//     Author: Rodney Shaghoulian
//     Github: github.com/RodneyShag
// HackerRank: hackerrank.com/RodneyShag

import java.util.Scanner;
import java.math.BigInteger;

/*

I use isProbablePrime() with certainty = 10 to achieve 99.9% accuracy. 
However, even certainty = 1 (which achieves 50% accuracy) is enough to 
pass the HackerRank test cases.

isProbablePrime() is always 100% certain if it tells you if a number 
is "not prime". If it says "prime", it's only 99.9% certain. It may be 
the case that it just hasn't found a prime number number that divides 
the BigInteger yet.

*/
public class Solution {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        BigInteger n = scan.nextBigInteger();
        scan.close();
        System.out.println(n.isProbablePrime(10) ? "prime" : "not prime");
    }
}