How to obtain an Executor?

Question

Reading this guide on how to analyze images fed directly from the camera; in the code example on the bottom of the page there suddenly pops up a new variable executor:

imageAnalysis.setAnalyzer(executor, ImageAnalysis.Analyzer { imageProxy ->

Looked it up, an Executor is just another parallelization abstraction. Now, how do I get one? Is there something like this?

androidThreadPool.getExecutor()

Actually, I found one:

Context.getMainExecutor()

If I understand this correctly, this would execute the Runnable on the main thread. However, I assume the point of providing an Executor to the ImageAnalyzer is to not run it on the main thread.

Or do I have to create my own Executor? Is this common practice to do so?

Answer 1

an Executor is just another parallelization abstraction

No, not “just another”. The Executors framework was a major milestone in the evolution of Java. This framework relieved the burden of managing threads from the shoulders of Java programmers, making concurrency work much simpler.

ExecutorService, not Executor

The Executor interface is not the most commonly used part. That interface defines the execute method which may run your task on a background thread or may just as well run the task on the current thread.

If you know you want a background thread, use an implementation of the ExecutorService sub-interface with its methods like submit.

how do I get one

Usually, we obtain an unspecified implementation of ExecutorService by calling a convenient factory method on the Executors class.

You may want an executor service backed by a pool of any number of threads. Use this only when you know you a limited number of simultaneous tasks, so as to not overburden your machine.

ExecutorService es = Executors.newCachedThreadPool() ;

You may want an executor service backed by a pool of a certain number threads.

ExecutorService es = Executors.newFixedThreadPool( maxThreadsCount ) ;

In modern Java, versions 21+, we use virtual threads for most purposes. I assume Android does not offer virtual threads, and won’t any time soon.

ExecutorService es = Executors.newVirtualThreadPerTaskExecutor() ;

Any of these executor services can run your tasks you define as either a Runnable or a Callable.

Or do I have to create my own Executor?

No, that would be a very rare situation where you would need a custom executor service.

Is [creating my own executor] common practice to do so?

No.

The purpose of the Executors framework is to avoid dealing with the low-level details of juggling threads and tasks. Several good implementations of ExecutorService are bundled with Java, made available to you via Executors class.

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Caveat: I don’t know Android. My comments here apply to the Java platform. My comments may also apply to Android; I just don’t know.