OnJava8-Examples/arrays/ParallelPrefix3.java

// arrays/ParallelPrefix3.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// {ValidateByHand} // CI Systems have trouble
import java.util.*;

public class ParallelPrefix3 {
  static final int SIZE = 10_000_000;
  public static void main(String[] args) {
    long[] nums = new long[SIZE];
    Arrays.setAll(nums, n -> n);
    Arrays.parallelPrefix(nums, Long::sum);
    System.out.println("First 20: " + nums[19]);
    System.out.println("First 200: " + nums[199]);
    System.out.println("All: " + nums[nums.length-1]);
  }
}
/* Output:
First 20: 190
First 200: 19900
All: 49999995000000
*/