Program not terminating when using Futures

Question

I\'m trying to concurrently run a function on each file in a directory. Sadly whenever I use Futures my program doesn\'t want to terminate (runs forever). I have tried using

Answer 1

Executors.newFixedThreadPool uses under the hood defaultThreadFactory which creates non-daemon thread

Returns a default thread factory used to create new threads. This factory creates all new threads used by an Executor in the same ThreadGroup... Each new thread is created as a non-daemon thread

Because these are non-daemon threads the program does not terminate. On the other hand, for example, scala.concurrent.ExecutionContext.Implicits.global creates daemon threads

val threadFactory = new DefaultThreadFactory(daemonic = true,
                                             maxBlockers = getInt("scala.concurrent.context.maxExtraThreads", "256"),
                                             prefix = "scala-execution-context-global",
                                             uncaught = (thread: Thread, cause: Throwable) => reporter(cause))

where we note daemonic = true, so the following program would terminate at the end

implicit val execContext = scala.concurrent.ExecutionContext.Implicits.global

val futures = for (file <- filesList) yield Future {
   println(file)
   // theFunc(file)
}
...

Based on

• https://stackoverflow.com/a/16612739/5205022
• https://stackoverflow.com/a/28086797/5205022