As far as I understand Guava's MoreExecutors.directExecutor() creates an Executor which will executes the runnable before the execute method call could return.
What are the usecases that need direct executor ? Can't the caller directly call runnable.run() directly instead of the extra level of indirection by creating an executor and submitting the runnable to this executor ? May be I am missing the real purpose of it's existence. I wanted to understand in what case is this useful.
There are few places which require both Runnable and Executor.
One of then is for example ListenableFuture and its addListener method. The only way how to execute listener immediately within the same thread is to provide direct executor.