我认为根据Aleksey和Rafael的建议展示一个实现会很有帮助。
关键变化：
我创建了两个示例，一个基于原始问题使用Serializable可以直接使用的数据集类，另一个测试每个人最喜欢的非序列化类，Optional.
如果 Aleksey 或 Rafael（或任何人）有任何建议，他们将不胜感激。
有Serializable数据集。
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Comparator;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Param;
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;
/**
* In this example each benchmark loops over the entire randomly generated data set.
* The same data set is used for all benchmarks.
* And we black hole the results.
*/
@SuppressWarnings("javadoc")
@State(Scope.Benchmark)
public class JmhBenchmark {
static final int DATA_SET_SAMPLE_SIZE = 1024 * 1024;
static final Random RANDOM = new Random();
static final Grisu g = Grisu.fmt;
double[] random_values;
double[] lowp_values;
byte[] bresults;
@Param("dataSetFilename")
String dataSetFilename;
@Setup
public void setup() throws FileNotFoundException, IOException, ClassNotFoundException {
try (FileInputStream fis = new FileInputStream(new File(this.dataSetFilename));
ObjectInputStream ois = new ObjectInputStream(fis)) {
final DataSet dataSet = (DataSet) ois.readObject();
this.random_values = dataSet.random_values;
this.lowp_values = dataSet.lowp_values;
}
this.bresults = new byte[30];
}
@Benchmark
public void test_rand_doubleto(final Blackhole bh) {
for (double random_value : this.random_values) {
bh.consume(Double.toString(random_value));
}
}
@Benchmark
public void test_lowp_doubleto(final Blackhole bh) {
for (double lowp_value : this.lowp_values) {
bh.consume(Double.toString(lowp_value));
}
}
@Benchmark
public void test_rand_grisustr(final Blackhole bh) {
for (double random_value : this.random_values) {
bh.consume(g.doubleToString(random_value));
}
}
@Benchmark
public void test_lowp_grisustr(final Blackhole bh) {
for (double lowp_value : this.lowp_values) {
bh.consume(g.doubleToString(lowp_value));
}
}
@Benchmark
public void test_rand_grisubuf(final Blackhole bh) {
for (double random_value : this.random_values) {
bh.consume(g.doubleToBytes(this.bresults, 0, random_value));
}
}
@Benchmark
public void test_lowp_grisubuf(final Blackhole bh) {
for (double lowp_value : this.lowp_values) {
bh.consume(g.doubleToBytes(this.bresults, 0, lowp_value));
}
}
/**
* Serializes an object containing random data. This data will be the same for all benchmarks.
* We pass the file name via the "dataSetFilename" parameter.
*
* @param args the arguments
*/
public static void main(final String[] args) {
try {
// clean up any old runs as data set files can be large
deleteTmpDirs(JmhBenchmark.class.getSimpleName());
// create a tempDir for the benchmark
final Path tempDirPath = createTempDir(JmhBenchmark.class.getSimpleName());
// create a data set file
final Path dateSetFilePath = Files.createTempFile(tempDirPath,
JmhBenchmark.class.getSimpleName() + "DataSet", ".ser");
final File dateSetFile = dateSetFilePath.toFile();
dateSetFile.deleteOnExit();
// create the data
final DataSet dataset = new DataSet();
try (FileOutputStream fos = new FileOutputStream(dateSetFile);
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
oos.writeObject(dataset);
oos.flush();
oos.close();
}
final Options opt = new OptionsBuilder().include(JmhBenchmark.class.getSimpleName())
.param("dataSetFilename", dateSetFile.getAbsolutePath())
.operationsPerInvocation(DATA_SET_SAMPLE_SIZE)
.mode(org.openjdk.jmh.annotations.Mode.All)
.timeUnit(TimeUnit.MICROSECONDS)
.forks(1)
.build();
new Runner(opt).run();
} catch (final Exception e) {
System.err.println(e.getMessage());
e.printStackTrace();
throw new RuntimeException(e);
}
}
static Path createTempDir(String prefix) throws IOException {
final Path tempDirPath = Files.createTempDirectory(prefix);
tempDirPath.toFile()
.deleteOnExit();
return tempDirPath;
}
static void deleteTmpDirs(final String prefix) throws IOException {
for (Path dir : Files.newDirectoryStream(new File(System.getProperty("java.io.tmpdir")).toPath(),
prefix + "*")) {
for (Path toDelete : Files.walk(dir)
.sorted(Comparator.reverseOrder())
.toArray(Path[]::new)) {
Files.delete(toDelete);
}
}
}
static final class DataSet implements Serializable {
private static final long serialVersionUID = 2194487667134930491L;
private static final int[] pows = new int[] { 1, 10, 100, 1000, 10000, 100000, 1000000 };
final double[] random_values = new double[DATA_SET_SAMPLE_SIZE];
final double[] lowp_values = new double[DATA_SET_SAMPLE_SIZE];
DataSet() {
for (int i = 0; i < DATA_SET_SAMPLE_SIZE; i++) {
this.random_values[i] = RANDOM.nextDouble();
}
for (int i = 0; i < DATA_SET_SAMPLE_SIZE; i++) {
this.lowp_values[i] = (1 + RANDOM.nextInt(10000)) / pows[RANDOM.nextInt(pows.length)];
}
}
}
}
使用不可序列化的测试对象 ( Optional)
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Comparator;
import java.util.List;
import java.util.Optional;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Param;
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;
@SuppressWarnings("javadoc")
@State(Scope.Benchmark)
public class NonSerializable {
static final int DATA_SET_SAMPLE_SIZE = 20000;
static final Random RANDOM = new Random();
Optional<Integer>[] optionals;
@Param("dataSetFilename")
String dataSetFilename;
@Setup
public void setup() throws FileNotFoundException, IOException, ClassNotFoundException {
try (FileInputStream fis = new FileInputStream(new File(this.dataSetFilename));
ObjectInputStream ois = new ObjectInputStream(fis)) {
@SuppressWarnings("unchecked")
List<Integer> strings = (List<Integer>) ois.readObject();
this.optionals = strings.stream()
.map(Optional::ofNullable)
.toArray(Optional[]::new);
}
}
@Benchmark
public void mapAndIfPresent(final Blackhole bh) {
for (int i = 0; i < this.optionals.length; i++) {
this.optionals[i].map(integer -> integer.toString())
.ifPresent(bh::consume);
}
}
@Benchmark
public void explicitGet(final Blackhole bh) {
for (int i = 0; i < this.optionals.length; i++) {
final Optional<Integer> optional = this.optionals[i];
if (optional.isPresent()) {
bh.consume(optional.get()
.toString());
}
}
}
/**
* Serializes a list of integers containing random data or null. This data will be the same for all benchmarks.
* We pass the file name via the "dataSetFilename" parameter.
*
* @param args the arguments
*/
public static void main(final String[] args) {
try {
// clean up any old runs as data set files can be large
deleteTmpDirs(NonSerializable.class.getSimpleName());
// create a tempDir for the benchmark
final Path tempDirPath = createTempDir(NonSerializable.class.getSimpleName());
// create a data set file
final Path dateSetFilePath = Files.createTempFile(tempDirPath,
NonSerializable.class.getSimpleName() + "DataSet", ".ser");
final File dateSetFile = dateSetFilePath.toFile();
dateSetFile.deleteOnExit();
final List<Integer> dataSet = IntStream.range(0, DATA_SET_SAMPLE_SIZE)
.mapToObj(i -> RANDOM.nextBoolean() ? RANDOM.nextInt() : null)
.collect(Collectors.toList());
try (FileOutputStream fos = new FileOutputStream(dateSetFile);
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
oos.writeObject(dataSet);
oos.flush();
oos.close();
}
final Options opt = new OptionsBuilder().include(NonSerializable.class.getSimpleName())
.param("dataSetFilename", dateSetFile.getAbsolutePath())
.operationsPerInvocation(DATA_SET_SAMPLE_SIZE)
.mode(org.openjdk.jmh.annotations.Mode.All)
.timeUnit(TimeUnit.MICROSECONDS)
.forks(1)
.build();
new Runner(opt).run();
} catch (final Exception e) {
System.err.println(e.getMessage());
e.printStackTrace();
throw new RuntimeException(e);
}
}
static Path createTempDir(String prefix) throws IOException {
final Path tempDirPath = Files.createTempDirectory(prefix);
tempDirPath.toFile()
.deleteOnExit();
return tempDirPath;
}
static void deleteTmpDirs(final String prefix) throws IOException {
for (Path dir : Files.newDirectoryStream(new File(System.getProperty("java.io.tmpdir")).toPath(),
prefix + "*")) {
for (Path toDelete : Files.walk(dir)
.sorted(Comparator.reverseOrder())
.toArray(Path[]::new)) {
Files.delete(toDelete);
}
}
}
}