Added 20 solutions

Java/BigNumber/Java Primality Test/Solution.java

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+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+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");
+    }
+}