Java Stream How to - Benchmark parallel Stream

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Question

We would like to know how to benchmark parallel Stream.

Answer

/*from   w w w  .j a v  a  2  s .  c om*/
import java.util.stream.IntStream;

public class Main {
  public static void main(String[] argv) {
    System.out.println("Benchmarking...");
    long t0 = System.nanoTime();

    int a[] = IntStream.range(0, 1_000_000).filter(p -> p % 2 == 0).toArray();
    long t1 = System.nanoTime();

    int b[] = IntStream.range(0, 1_000_000).parallel().filter(p -> p % 2 == 0)
        .toArray();
    long t2 = System.nanoTime();
    
    System.out.printf("serial: %.2fs, parallel %.2fs%n", (t1 - t0) * 1e-9, (t2 - t1) * 1e-9);
  }
}

The code above generates the following result.

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