Comment on http://www.javacodegeeks.com/2015/07/java-performance-tutorial-how-fast-are-the-java-8-streams.html

MyBenchmark.java

import java.util.*; 
import java.util.stream.*; 
import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.annotations.*;
 
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@Fork(2)
@State(Scope.Benchmark)
public class MyBenchmark {
    @Param({"5000", "50000", "500000"})
    private int n;

    private int[] ints;

    @Setup
    public void setup() {
        ints = new Random(1).ints(n).toArray();
    }

    @Benchmark
    public void stream(Blackhole bh) {
        bh.consume(Arrays.stream(ints).reduce(Integer.MIN_VALUE, Math::max));
    }

    @Benchmark
    public void streamParallel(Blackhole bh) {
        bh.consume(Arrays.stream(ints).parallel().reduce(Integer.MIN_VALUE, Math::max));
    }

    @Benchmark
    public void simple(Blackhole bh) {
        int[] a = ints;
        int e = ints.length;
        int m = Integer.MIN_VALUE;
        for(int i=0; i < e; i++)   if(a[i] > m) m = a[i];
        bh.consume(m);
    }
}

results.txt

# JMH 1.10.1 (released 34 days ago)
# VM invoker: C:\Program Files\Java\jdk1.8.0_40\jre\bin\java.exe

Benchmark                      (n)  Mode  Cnt    Score    Error  Units
MyBenchmark.simple            5000  avgt   20    1.305 ±  0.080  us/op
MyBenchmark.simple           50000  avgt   20   12.949 ±  0.223  us/op
MyBenchmark.simple          500000  avgt   20  131.875 ±  4.914  us/op
MyBenchmark.stream            5000  avgt   20    5.259 ±  0.051  us/op
MyBenchmark.stream           50000  avgt   20   57.328 ±  5.345  us/op
MyBenchmark.stream          500000  avgt   20  656.991 ± 29.502  us/op
MyBenchmark.streamParallel    5000  avgt   20    8.408 ±  1.852  us/op
MyBenchmark.streamParallel   50000  avgt   20   20.290 ±  3.579  us/op
MyBenchmark.streamParallel  500000  avgt   20  102.484 ±  9.909  us/op