Virtual threads make thousands of tasks cheap

Java 21 virtual threads are scheduled by the JVM, not the OS, so blocking work scales to very large numbers of concurrent tasks with ordinary blocking code.

Code

var counter = new AtomicInteger();

try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    for (int i = 0; i < 10_000; i++) {
        executor.submit(() -> {
            Thread.sleep(Duration.ofMillis(5));   // blocking is fine on a virtual thread
            counter.incrementAndGet();
            return null;
        });
    }
}   // close() waits for every task to finish

System.out.println("completed tasks = " + counter.get());

Output

completed tasks = 10000

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Published 2026-07-30