TZTest.java

/*
$ export TZ=UTC

TZ = UTC
Benchmark          Mode  Cnt   Score   Error  Units
TZTest.currentTimeMillis  avgt    5  40.014 ± 1.383  ns/op
TZTest.instant            avgt    5  47.798 ± 0.669  ns/op
TZTest.nano               avgt    5  40.747 ± 1.040  ns/op

$ unset TZ

TZ = null
Benchmark                 Mode  Cnt   Score   Error  Units
TZTest.currentTimeMillis  avgt    5  39.858 ± 0.116  ns/op
TZTest.instant            avgt    5  47.785 ± 1.476  ns/op
TZTest.nano               avgt    5  40.431 ± 0.699  ns/op

 */
package com;

import java.time.Instant;
import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Threads;
import org.openjdk.jmh.annotations.Warmup;
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;

/**
 * @author vladimir.dolzhenko
 * @since 2017-02-22
 */
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(1)
@Warmup(iterations = 2, time = 5000, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 5, time = 5000, timeUnit = TimeUnit.MILLISECONDS)
@Threads(1)
@State(Scope.Benchmark)
public class TZTest {

    @Benchmark
    public long nano() {
        return System.nanoTime();
    }

    @Benchmark
    public long currentTimeMillis() {
        return System.currentTimeMillis();
    }

    @Benchmark
    public Instant instant() {
        return Instant.now();
    }

    public static void main(String[] args) throws RunnerException {
        System.out.println("TZ = " + System.getenv("TZ"));
        Options opt = new OptionsBuilder()
                .include(TZTest.class.getSimpleName())
                .build();

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