Small Change to Java implementation of Monte Carlo (#210)

Changed the monteCarlo function to return a double so print statements are done in main()

I think the code is a bit cleaner this way but it may just be a personal preference so I understand if this isn't merged

Author: Wesley-Arrington

chapters/monte_carlo/code/java/MonteCarlo.java

@@ -4,7 +4,9 @@
 public class MonteCarlo {
 
     public static void main(String[] args) {
-        monteCarlo(10_000_000);
+        double piEstimation = monteCarlo(1000);
+        System.out.println("Estimated pi value: " + piEstimation);
+        System.out.printf("Percent error: " + 100 * (Math.PI - piEstimation) / Math.PI);
     }
 
     //function to check whether point (x,y) is in unit circle
@@ -13,7 +15,7 @@ private static boolean inCircle(double x, double y) {
     }
 
     //function to calculate estimation of pi
-    public static void monteCarlo(int samples) {
+    public static double monteCarlo(int samples) {
         int piCount = 0;
 
         Random random = new Random();
@@ -27,9 +29,6 @@ public static void monteCarlo(int samples) {
         }
 
         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);
+        return estimation;
     }
 }

chapters/monte_carlo/monte_carlo.md

@@ -54,7 +54,7 @@ each point is tested to see whether it's in the circle or not:
 {% sample lang="go" %}
 [import:12-14, lang:"golang"](code/go/monteCarlo.go)
 {% sample lang="java" %}
-[import:11-13, lang:"java"](code/java/MonteCarlo.java)
+[import:13-15, lang:"java"](code/java/MonteCarlo.java)
 {% sample lang="swift" %}
 [import:21-25, lang:"swift"](code/swift/monte_carlo.swift)
 {% endmethod %}