Benchmark.java

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.stream.IntStream;

/**
* Using JDK 8 build b129
*/

@State(Scope.Thread)
public class Benchmark {

    List<Person> persons = new ArrayList<>();

    @Setup
    public void init() {
        Random random = new Random();

        IntStream.range(0, 10000).forEach( a -> {
            persons.add(new Person(random.nextInt(100)));
        });
    }

    @GenerateMicroBenchmark
    public void non_functional() {
        long sum = 0;
        for (Person person : persons) {
            sum += person.age;
        }
    }

    @GenerateMicroBenchmark
    public void functional() {
        persons.stream().map( p -> p.age ).reduce( (a, b) -> a + b ).get();
    }


    public static void main(String[] args) throws RunnerException {
        Options options = new OptionsBuilder()
                .include(".*" + Benchmark.class.getSimpleName() + ".*")
                .shouldDoGC(true)
                .shouldFailOnError(true)
                .mode(Mode.All)
                .warmupIterations(1)
                .measurementIterations(10)
                .forks(1)
                .build();

        new Runner(options).run();
    }


    /**
     *
     */
    static class Person {
        Person(int age) {
            this.age = age;
        }

        int age;
    }

}

JMH_result

Machine: OSx 10.9.1 (3 GHz Intel Core i7, L2 Cache 256 KB, L3 Cache 4 MB)
JMH version 0.2.1

Benchmark                      Mode   Samples         Mean   Mean error    Units

s.Benchmark.functional        thrpt        10        9.561        0.184   ops/ms
s.Benchmark.non_functional    thrpt        10      123.471        3.601   ops/ms

s.Benchmark.functional         avgt        10        0.122        0.001    ms/op
s.Benchmark.non_functional     avgt        10        0.008        0.000    ms/op

s.Benchmark.functional       sample     94905        0.105        0.000    ms/op
s.Benchmark.non_functional   sample   1202292        0.008        0.000    ms/op

s.Benchmark.functional           ss        10        0.499        0.250       ms
s.Benchmark.non_functional       ss        10        0.678        0.475       ms