Java - Pattern matching and virtual threads in Java 19 preview
Java 19 preview improved the pattern matching language feature. The following code shows how we can leverage them with virtual threads.
Full code can be found from the github
The demo code is trying to find the quickest website on landing page.
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package org.demo;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.time.Duration;
import java.time.Instant;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.stream.Stream;
/**
* Date ${DATE}
*
* @author Nam Seob Seo
*/
public class Main {
sealed interface IResult<T> {
record Success<T>(T data) implements IResult<T> {}
record Failed<T>(Exception exception) implements IResult<T> {}
}
record URLData(URL url, byte[] response, long durationMs) { }
IResult<URLData> fromFuture(Future<IResult<URLData>> future) {
try {
IResult<URLData> result = future.get();
return switch(result) {
case IResult.Success<URLData> s -> s;
case IResult.Failed<URLData> f -> {
System.out.println("failed: %s".formatted(f.exception.getMessage()));
yield f;
}
};
} catch (InterruptedException | ExecutionException e) {
return new IResult.Failed<>(e);
}
}
IResult<URLData> fetchUrlData(URL url) {
try (InputStream in = url.openStream()) {
try {
Instant start = Instant.now();
System.out.println("started: %s".formatted(url.toString()));
var bytes = in.readAllBytes();
var duration = Duration.between(start, Instant.now()).toMillis();
System.out.println("finished: %s(%dms)".formatted(url.toString(), duration));
return new IResult.Success<>(new URLData(url, bytes, duration));
} catch (Exception e) {
return new IResult.Failed<>(e);
}
} catch (IOException e) {
return new IResult.Failed<>(e);
}
}
List<URLData> retrieveURLs(List<URL> urls) {
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
var tasks = urls
.stream()
.map(url -> executor.submit(() -> fetchUrlData(url)))
.toList();
System.out.println("%d tasks have been created".formatted(tasks.size()));
return tasks.stream().map(this::fromFuture)
.map(s -> s instanceof IResult.Success<URLData>(URLData d) ? d : null)
.filter(Objects::nonNull)
.toList();
}
}
static String toJson(List<URLData> result) {
var list = result.stream()
.sorted(Comparator.comparingLong(x -> x.durationMs))
.map(data ->
"""
{
"url": "%s",
"duration:: "%d(ms)",
"size": "%d(KB)"
}""".formatted(data.url, data.durationMs, data.response.length / 1024))
.toList();
return """
[
%s
]""".formatted(String.join(",", list));
}
public static void main(String[] args) {
List<URL> urls = Stream.of(
"https://www.google.com",
"https://www.youtube.com",
"https://www.yahoo.com",
"https://www.github.com",
"https://www.linkedin.com",
"https://www.amazon.com",
"https://www.bing.com",
"https://www.reddit.com",
"https://www.mozilla.org",
"https://www.facebook.com",
"https://www.ebay.com",
"https://www.twitter.com",
"https://www.cloudflare.com",
"https://www.datadoghq.com")
.map(url -> {
try {
return new URL(url);
} catch (MalformedURLException e) {
throw new RuntimeException(e);
}
}).toList();
List<URLData> result = new Main().retrieveURLs(urls);
System.out.println(toJson(result));
}
}