Fire And Forget Task (ARCH4021)

Key java.async.ignored-future · Severity warning · Category async

When a CompletableFuture or task is produced as a bare expression statement and never awaited, assigned, or returned, its exceptions are lost and its ordering is undefined. The result is never observed.

Incorrect

void process(List<Order> orders) {
    for (Order o : orders) {
        CompletableFuture.runAsync(() -> save(o)); // result ignored
    }
}

Correct

void process(List<Order> orders) {
    List<CompletableFuture<Void>> futures = new ArrayList<>();
    for (Order o : orders) {
        futures.add(CompletableFuture.runAsync(() -> save(o)));
    }
    CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
}

Fix

Assign the produced future and wait on it with join()/get(), or return it to the caller.