content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.spark.examples;
  
  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.sql.SparkSession;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Computes an approximation to pi
   * Usage: JavaSparkPi [slices]
   */
  public final class JavaSparkPi {
  
    public static void main(String[] args) throws Exception {
      SparkSession spark = SparkSession
        .builder()
        .appName("JavaSparkPi")
        .getOrCreate();
  
      JavaSparkContext jsc = new JavaSparkContext(spark.sparkContext());
  
      int slices = (args.length == 1) ? Integer.parseInt(args[0]) : 2;
      int n = 100000 * slices;
      List<Integer> l = new ArrayList<>(n);
      for (int i = 0; i < n; i++) {
        l.add(i);
      }
  
      JavaRDD<Integer> dataSet = jsc.parallelize(l, slices);
  
      int count = dataSet.map(new Function<Integer, Integer>() {
        @Override
        public Integer call(Integer integer) {
          double x = Math.random() * 2 - 1;
          double y = Math.random() * 2 - 1;
          return (x * x + y * y < 1) ? 1 : 0;
        }
      }).reduce(new Function2<Integer, Integer, Integer>() {
        @Override
        public Integer call(Integer integer, Integer integer2) {
          return integer + integer2;
        }
      });
  
      System.out.println("Pi is roughly " + 4.0 * count / n);
  
      spark.stop();
    }
  }
  