Bael 43 (#6423)

* BAEL-43: Apache Spark with Spring Cloud Data Flow

* Replaced functions with lambdas + removed unnecessary type casting.

spring-cloud-data-flow/apache-spark-job/src/main/java/com/baeldung/spring/cloud/PiApproximation.java

@@ -0,0 +1,39 @@
+package com.baeldung.spring.cloud;
+
+import org.apache.spark.SparkConf;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.Function;
+import org.apache.spark.api.java.function.Function2;
+import org.apache.spark.rdd.RDD;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+public class PiApproximation {
+    public static void main(String[] args) {
+        SparkConf conf = new SparkConf().setAppName("BaeldungPIApproximation");
+        JavaSparkContext context = new JavaSparkContext(conf);
+        int slices = args.length >= 1 ? Integer.valueOf(args[0]) : 2;
+        int n = (100000L * slices) > Integer.MAX_VALUE ? Integer.MAX_VALUE : 100000 * slices;
+
+        List<Integer> xs = IntStream.rangeClosed(0, n)
+          .mapToObj(element -> Integer.valueOf(element))
+          .collect(Collectors.toList());
+
+        JavaRDD<Integer> dataSet = context.parallelize(xs, slices);
+
+        JavaRDD<Integer> pointsInsideTheCircle = dataSet.map(integer -> {
+           double x = Math.random() * 2 - 1;
+           double y = Math.random() * 2 - 1;
+           return (x*x + y*y ) < 1 ? 1: 0;
+        });
+
+        int count = pointsInsideTheCircle.reduce((integer, integer2) -> integer + integer2);
+
+        System.out.println("The pi was estimated as:" + count / n);
+
+        context.stop();
+    }
+}