// Virtual Threads (Java 21+)
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    IntStream.range(0, 10_000).forEach(i ->
        executor.submit(() -> processRequest(i)));
}

// CompletableFuture composition
CompletableFuture<Result> result = fetchUser(id)
    .thenCompose(user -> fetchOrders(user.id()))
    .thenApply(orders -> processOrders(orders))
    .exceptionally(ex -> handleError(ex))
    .orTimeout(5, TimeUnit.SECONDS);

// Thread pool configuration
ThreadPoolExecutor executor = new ThreadPoolExecutor(
    10, 50, 60L, TimeUnit.SECONDS,
    new ArrayBlockingQueue<>(1000),
    new ThreadPoolExecutor.CallerRunsPolicy()
);

// Lock with timeout
ReentrantLock lock = new ReentrantLock();
if (lock.tryLock(1, TimeUnit.SECONDS)) {
    try {
        // critical section
    } finally {
        lock.unlock();
    }
}

jstack -l <pid> > threaddump.txt
jcmd <pid> Thread.print

Skill("java-concurrency")