Added class that calculated Pi (#2324)

* added class PiNilakantha.java
which calculates Pi using Nilakanthas infinite series

* added link to explanation
partially fixes #2323

Maths/PiNilakantha.java

@@ -0,0 +1,46 @@
+package Maths;
+
+public class PiNilakantha {
+
+    // Calculates Pi using Nilakantha's infinite series
+    // Method 2 in the following link explains the algorithm
+    //https://en.scratch-wiki.info/wiki/Calculating_Pi
+
+
+    public static void main(String[] args) {
+        assert calculatePi(0) == 3.0;
+        assert calculatePi(10) > 3.0;
+        assert calculatePi(100) < 4.0;
+
+        System.out.println(calculatePi(500));
+    }
+
+
+    /**
+     *
+     * @param iterations number of times the infinite series gets repeated
+     *        Pi get more accurate the higher the value of iterations is
+     *        Values from 0 up to 500 are allowed since double precision is not sufficient
+     *        for more than about 500 repetitions of this algorithm
+     * @return the pi value of the calculation with a precision of x iteration
+     */
+    public static double calculatePi(int iterations) {
+        if (iterations < 0 || iterations > 500) {
+            throw new IllegalArgumentException("Please input Integer Number between 0 and 500");
+        }
+
+        double pi = 3;
+        int divCounter = 2;
+
+        for (int i = 0; i < iterations; i++) {
+
+            if (i % 2 == 0)
+                pi = pi + 4.0 / (divCounter * (divCounter + 1) * (divCounter + 2));
+            else
+                pi = pi - 4.0 / (divCounter * (divCounter + 1) * (divCounter + 2));
+
+            divCounter += 2;
+        }
+        return pi;
+    }
+}