Futures.whenAllComplete(...).run()

~6% of callers of our old Futures.combine either pass a Callable<Void>, ignore the result of combine, or both. Some of these might need to use Callable because they throw checked exceptions, but others would probably prefer not to write the extra boilerplate (mostly return null but also <Void>).

We could help them out by providing run(Runnable) alongside call(Callable). We could still return ListenableFuture<?> for users who need to check for errors or await the result.

6% is a small percentage, but the API is also very low cost (easy to understand and “hidden” in the FutureCombiner type). It would also match the overloads of ExecutorService.submit.

[cpovirk]

(This would also let people write expression lambdas instead of block lambdas in some cases.)

[cpovirk]

Unfortunately it’s an internal-only process. But this addition should be straightforward enough, so I’ll try to take care of it when I have a spare moment.