[mrkeen]

> optional interrupt send to the thread running the blocking operation

I'm not 100% sure on what you mean by an optional interrupt, but I'm guessing it's the boolean flag on the cancel(); Let's look!

    public boolean cancel(boolean mayInterruptIfRunning) {
        boolean cancelled = this.result == null && this.internalComplete(new CompletableFuture.AltResult(new CancellationException()));
        this.postComplete();
        return cancelled || this.isCancelled();
    }

Doesn't look like it's used.

[lenkite]

You are right. Even the javadoc says that `CompletableFuture` doesn't support this. Bah! will force me read the fine print next time.

mayInterruptIfRunning - this value has no effect in this implementation because interrupts are not used to control processing.