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🏷 Virtual Threads 5 patterns

Topic: Virtual Threads

All Java patterns related to Virtual Threads — java.evolved

Virtual thread executor

Old ExecutorService exec = Executors.newFixedThreadPool(10); try { futures = tasks.stream() .map(t -> exec.submit(t)) .toList(); } finally { exec.shutdown(); }

Modern try (var exec = Executors .newVirtualThreadPerTaskExecutor()) { var futures = tasks.stream() .map(exec::submit) .toList(); }

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JDK 21+ learn more →

Virtual threads

Old Thread thread = new Thread(() -> { System.out.println("hello"); }); thread.start(); thread.join();

Modern Thread.startVirtualThread(() -> { IO.println("hello"); }).join();

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JDK 21+ learn more →

Structured concurrency

Old ExecutorService exec = Executors.newFixedThreadPool(2); Future<User> u = exec.submit(this::fetchUser); Future<Order> o = exec.submit(this::fetchOrder); try { return combine(u.get(), o.get()); } finally { exec.shutdown(); }

Modern try (var scope = new StructuredTaskScope .ShutdownOnFailure()) { var u = scope.fork(this::fetchUser); var o = scope.fork(this::fetchOrder); scope.join().throwIfFailed(); return combine(u.get(), o.get()); }

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JDK 25+ learn more →

Scoped values

Old static final ThreadLocal<User> CURRENT = new ThreadLocal<>(); void handle(Request req) { CURRENT.set(authenticate(req)); try { process(); } finally { CURRENT.remove(); } }

Modern static final ScopedValue<User> CURRENT = ScopedValue.newInstance(); void handle(Request req) { ScopedValue.where(CURRENT, authenticate(req) ).run(this::process); }

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JDK 25+ learn more →

Concurrent HTTP with virtual threads

Old ExecutorService pool = Executors.newFixedThreadPool(10); List<Future<String>> futures = urls.stream() .map(u -> pool.submit( () -> fetchUrl(u))) .toList(); // manual shutdown, blocking get()

Modern try (var exec = Executors .newVirtualThreadPerTaskExecutor()) { var results = urls.stream() .map(u -> exec.submit( () -> client.send(req(u), ofString()).body())) .toList().stream() .map(Future::join).toList(); }

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JDK 21+ learn more →