Virtual threads: invokeAll gathers results

ExecutorService.invokeAll submits every task and blocks until all are done, which gives a simple fork-join shape over virtual threads.

Code

List<Callable<Integer>> tasks = IntStream.rangeClosed(1, 5)
        .mapToObj(n -> (Callable<Integer>) () -> {
            Thread.sleep(Duration.ofMillis(10));
            return n * n;
        })
        .toList();

try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    List<Future<Integer>> futures = executor.invokeAll(tasks);
    int total = 0;
    for (Future<Integer> f : futures) total += f.get();
    System.out.println("squares of 1..5 sum to " + total);
}

Output

squares of 1..5 sum to 55

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Published 2026-07-30