MapIteration

package net.mojang.benchmark;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
import org.openjdk.jmh.runner.options.TimeValue;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Thread;

public class MapIteration {

    /**
     * Benchmark                  Mode  Cnt      Score       Error   Units
     * MapIteration.enhancedFor  thrpt    3  26560.045 ±  1348.768  ops/ms
     * MapIteration.lambda       thrpt    3  44321.144 ± 14483.751  ops/ms
     */
    
    @State(Scope.Benchmark)
    public static class BenchmarkState {
        final Map<String, String> map = new HashMap<>();

        @Setup
        public void setup() {
            map.put("1", "one");
            map.put("2", "two");
            map.put("3", "three");
        }
    }

    @Benchmark
    public void lambda(final Blackhole blackhole, final BenchmarkState state) {
        state.map.forEach((key, value) -> {
            blackhole.consume(key);
            blackhole.consume(value);
        });
    }

    @Benchmark
    public void enhancedFor(final Blackhole blackhole, final BenchmarkState state) {
        for (final Map.Entry<String, String> entry : state.map.entrySet()) {
            blackhole.consume(entry.getKey());
            blackhole.consume(entry.getValue());
        }
    }

    public static void main(final String[] args) throws Exception {
        final Options opt = new OptionsBuilder()
            .include(MapIteration.class.getName() + ".*")
            .mode(Mode.Throughput)
            .timeUnit(TimeUnit.MILLISECONDS)
            .warmupTime(TimeValue.seconds(20))
            .warmupIterations(3)
            .measurementTime(TimeValue.seconds(20))
            .measurementIterations(3)
            .threads(1)
            .forks(1)
            .detectJvmArgs()
            .shouldFailOnError(true)
            .shouldDoGC(true)
            .build();

        new Runner(opt).run();
    }
}