Using cats-effect's MapRef, full control

FullControlMapRef.scala

//> using scala 3.3
//> using dep org.typelevel::cats-effect:3.5.4

import cats.syntax.all.*
import cats.effect.{IO, IOApp}
import cats.effect.std.MapRef

import java.util.concurrent.{ConcurrentHashMap => JConcurrentHashMap}

object FullControlMapRef extends IOApp.Simple:

  val fullControlSample =
    def getKeys(jchm: JConcurrentHashMap[Int, String]): IO[List[Int]] =
      import scala.jdk.CollectionConverters.*
      IO(jchm.keys()).map(_.asScala.toList)
    def printKeys(jchm: JConcurrentHashMap[Int, String]): IO[Unit] =
      getKeys(jchm).map(_.mkString("keys: [", ", ", "]")) >>= IO.println
    for
      jchm <- IO(JConcurrentHashMap[Int, String]())
      mr = MapRef.fromConcurrentHashMap[IO, Int, String](jchm)
      _ <- (1 to 20).map(k => mr.setKeyValue(k, k.toString)).toList.parSequence // Set values concurrently
      _ <- printKeys(jchm) // Will print a list with the 20 keys
      _ <- (1 to 20).map(k => mr.unsetKey(k)).toList.parSequence // Remove values concurrently
      _ <- printKeys(jchm) // Will print an empty list
    yield ()

  override val run = fullControlSample