Added MonteCarlo in Java (#188)

* Added monte carlo method in Java

* fixed number of lines in md file

* Set fixed radius to 1

* Corrected code style

Author: DominikRafacz

CONTRIBUTORS.md

@@ -13,3 +13,4 @@ Chinmaya Mahesh
 Unlambder
 Kjetil Johannessen
 CDsigma
+DominikRafacz

chapters/monte_carlo/code/java/MonteCarlo.java

@@ -0,0 +1,35 @@
+//submitted by DominikRafacz
+import java.util.Random;
+
+public class MonteCarlo {
+
+    public static void main(String[] args) {
+        monteCarlo(10_000_000);
+    }
+
+    //function to check whether point (x,y) is in unit circle
+    private static boolean inCircle(double x, double y) {
+        return x * x + y * y < 1;
+    }
+
+    //function to calculate estimation of pi
+    public static void monteCarlo(int samples) {
+        int piCount = 0;
+
+        Random random = new Random();
+
+        for (int i = 0; i < samples; i++) {
+            double x = random.nextDouble();
+            double y = random.nextDouble();
+            if (inCircle(x, y)) {
+                piCount++;
+            }
+        }
+
+        double estimation = 4.0 * piCount / samples;
+
+        System.out.println("Estimated pi value: " + estimation);
+        System.out.printf("Percent error: %.4f%%",  
+                          100 * (Math.PI - estimation) / Math.PI);
+    }
+}

chapters/monte_carlo/monte_carlo.md

@@ -53,6 +53,8 @@ each point is tested to see whether it's in the circle or not:
 [import:2-5, lang:"d"](code/d/monte_carlo.d)
 {% sample lang="go" %}
 [import:12-14, lang:"golang"](code/go/monteCarlo.go)
+{% sample lang="java" %}
+[import:11-13, lang:"java"](code/java/MonteCarlo.java)
 {% endmethod %}
 
 If it's in the circle, we increase an internal count by one, and in the end,
@@ -108,6 +110,9 @@ Feel free to submit your version via pull request, and thanks for reading!
 {%sample lang="go" %}
 ### Go
 [import, lang:"golang"](code/go/monteCarlo.go)
+{% sample lang="java" %}
+### Java
+[import, lang:"java"](code/java/MonteCarlo.java)
 {% endmethod %}