Java: single-threaded sub-Artist as part of another multi-threaded Artist

Question

I would like to accomplish some tasks in a serialized way. A typical solution for this is to create

Executor executor = Executors.newSingleThreadedExecutor();

and run tasks on it.

However, I already have a thread pool that is multithreaded.

Is there a simple way to get a sub-executor that behaves as a single-threaded (like in: runs only one task at a time), but uses another (possibly not single-threaded) executor as a “backend” instead of creating a completely new OS thread?

There are several use cases for why we would like to do this:

• an application may already have a thread pool, for example. background tasks, with a given priority, etc. that we would like to reuse.
• Similarly, we can pass to Executor, which is not just a pool of threads (for example, delaying execution for subsequent measurement of runtime, etc.),
  • a subset of which is passed to MoreExecutors.directExecutor () for testing (so, for example, Futures is resolved immediately).

EDIT : added above examples

Answer 1

Such a zero-threaded operator is called SerialExecutorand described in the java documentation before java.util.concurrent.Executor. However, it has a slight flaw: for each sent one, Runnableit creates a wrapper object. My own implementation does not create additional objects.

Answer 2

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