Port java.util.concurrent.ForkJoinPool from JSR-166 (#3136)

Ports `ForkJoinPool` and other required types from `java.util.concurrent` types: 
* `AbstractExecutorService`
* `Callable` 
* `CompletionService`
* `CountedCompleter`
* `Executor`
* `ExecutorCompletionService`
* `ExecutorService`
* `Executors` (partially)
* `ForkJoinPool`
* `ForkJoinTask`
* `ForkJoinWorkerThread`
* `Future`
* `FutureTask`
* `RecursiveAction`
* `RecursiveTask`
* `RejectedExecutionHandler`
* `RunnableFuture`
* `ThreadFactory`

* Add missing `java.util.concurrent.TimeUnit` methods
* Don't report deprecation warning in `ThreadTest`
* Run scalafmt
* Disable JVM tests failing on JDK 8

javalib/src/main/scala-2/java/util/concurrent/TimeUnit.scala

@@ -16,6 +16,13 @@ abstract class TimeUnit private (name: String, ordinal: Int)
   def toMinutes(a: Long): Long
   def toHours(a: Long): Long
   def toDays(a: Long): Long
+
+  def sleep(timeout: Long): Unit =
+    if (timeout > 0) Thread.sleep(toMillis(timeout))
+  def timedJoin(thread: Thread, timeout: Long) =
+    if (timeout > 0) thread.join(toMillis(timeout))
+  def timedWait(obj: Object, timeout: Long) =
+    if (timeout > 0) obj.wait(toMillis(timeout))
 }
 
 object TimeUnit {

javalib/src/main/scala-3/java/util/concurrent/TimeUnit.scala

@@ -16,6 +16,13 @@ enum TimeUnit extends Enum[TimeUnit] {
   case HOURS extends TimeUnit
   case DAYS extends TimeUnit
 
+  def sleep(timeout: Long): Unit =
+    if (timeout > 0) Thread.sleep(toMillis(timeout))
+  def timedJoin(thread: Thread, timeout: Long) =
+    if (timeout > 0) thread.join(toMillis(timeout))
+  def timedWait(obj: Object, timeout: Long) =
+    if (timeout > 0) obj.wait(toMillis(timeout))
+
   def convert(a: Long, u: TimeUnit): Long = this match {
     case TimeUnit.NANOSECONDS  => u.toNanos(a)
     case TimeUnit.MICROSECONDS => u.toMicros(a)

javalib/src/main/scala/java/util/concurrent/AbstractExecutorService.scala

@@ -0,0 +1,248 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent
+
+import java.util
+import java.lang
+import java.util.concurrent.TimeUnit._
+import scala.annotation.tailrec
+
+abstract class AbstractExecutorService() extends ExecutorService {
+
+  protected[concurrent] def newTaskFor[T <: AnyRef](
+      runnable: Runnable,
+      value: T
+  ): RunnableFuture[T] =
+    new FutureTask[T](runnable, value)
+
+  protected[concurrent] def newTaskFor[T <: AnyRef](
+      callable: Callable[T]
+  ): RunnableFuture[T] =
+    new FutureTask[T](callable)
+
+  @throws[NullPointerException]
+  @throws[java.lang.RejectedExecutionException]
+  override def submit(task: Runnable): Future[_] = {
+    if (task == null) throw new NullPointerException()
+    val ftask: RunnableFuture[Object] = newTaskFor(task, null)
+    execute(ftask)
+    ftask
+  }
+
+  @throws[NullPointerException]
+  @throws[java.lang.RejectedExecutionException]
+  override def submit[T <: AnyRef](task: Runnable, result: T): Future[T] = {
+    if (task == null) throw new NullPointerException()
+    val ftask: RunnableFuture[T] = newTaskFor(task, result)
+    execute(ftask)
+    ftask
+  }
+
+  @throws[NullPointerException]
+  @throws[java.lang.RejectedExecutionException]
+  override def submit[T <: AnyRef](task: Callable[T]): Future[T] = {
+    if (task == null) throw new NullPointerException()
+    val ftask: RunnableFuture[T] = newTaskFor(task)
+    execute(ftask)
+    ftask
+  }
+
+  @throws[InterruptedException]
+  @throws[TimeoutException]
+  @throws[ExecutionException]
+  private def doInvokeAny[T <: AnyRef](
+      tasks: util.Collection[_ <: Callable[T]],
+      timed: Boolean,
+      n: Long
+  ): T = {
+    var nanos: Long = n
+    if (tasks == null)
+      throw new NullPointerException()
+
+    var ntasks: Int = tasks.size()
+    if (ntasks == 0)
+      throw new IllegalArgumentException()
+
+    val futures = new util.ArrayList[Future[T]](ntasks)
+    val ecs = new ExecutorCompletionService[T](this)
+
+    // For efficiency, especially in executors with limited
+    // parallelism, check to see if previously submitted tasks are
+    // done before submitting more of them. This interleaving
+    // plus the exception mechanics account for messiness of main
+    // loop.
+
+    try {
+      // Record exceptions so that if we fail to obtain any
+      // result, we can throw the last exception we got.
+      var ee: ExecutionException = null
+      val deadline = if (timed) System.nanoTime() + nanos else 0L
+      val it = tasks.iterator()
+
+      // Start one task for sure; the rest incrementally
+      futures.add(ecs.submit(it.next()))
+      ntasks -= 1
+      var active: Int = 1
+
+      var break: Boolean = false
+      while (!break) {
+        val f: Future[T] = ecs.poll() match {
+          case null =>
+            if (ntasks > 0) {
+              ntasks -= 1
+              futures.add(ecs.submit(it.next()))
+              active += 1
+              null
+            } else if (active == 0) {
+              break = true
+              null
+            } else if (timed)
+              ecs.poll(nanos, TimeUnit.NANOSECONDS) match {
+                case null => throw new TimeoutException()
+                case f =>
+                  nanos = deadline - System.nanoTime()
+                  f
+              }
+            else ecs.take()
+
+          case f => f
+        }
+        if (!break && f != null) {
+          active -= 1
+          try {
+            return f.get()
+          } catch {
+            case eex: ExecutionException => ee = eex
+            case rex: RuntimeException   => ee = new ExecutionException(rex)
+          }
+        }
+      }
+      if (ee == null) ee = new ExecutionException(null: Throwable)
+      throw ee
+    } finally cancelAll(futures)
+  }
+
+  @throws[InterruptedException]
+  @throws[ExecutionException]
+  override def invokeAny[T <: AnyRef](
+      tasks: util.Collection[_ <: Callable[T]]
+  ): T =
+    doInvokeAny(tasks, false, 0)
+
+  @throws[InterruptedException]
+  @throws[ExecutionException]
+  @throws[TimeoutException]
+  override def invokeAny[T <: AnyRef](
+      tasks: java.util.Collection[_ <: Callable[T]],
+      timeout: Long,
+      unit: TimeUnit
+  ): T = doInvokeAny(tasks, true, unit.toNanos(timeout))
+
+  @throws[InterruptedException]
+  override def invokeAll[T <: AnyRef](
+      tasks: java.util.Collection[_ <: Callable[T]]
+  ): java.util.List[Future[T]] = {
+    if (tasks == null) throw new NullPointerException()
+    val futures: util.List[Future[T]] =
+      new util.ArrayList[Future[T]](tasks.size())
+    var done: Boolean = false
+    try {
+      val it = tasks.iterator()
+      while (it.hasNext()) {
+        val f: RunnableFuture[T] = newTaskFor(it.next())
+        futures.add(f)
+        execute(f)
+      }
+
+      val it1 = futures.iterator()
+      while (it1.hasNext()) {
+        val f = it1.next()
+        if (!f.isDone()) {
+          try {
+            f.get()
+          } catch {
+            case ignore: CancellationException =>
+            case ignore: ExecutionException    =>
+          }
+        }
+      }
+      done = true
+      futures
+    } finally if (!done) cancelAll(futures)
+  }
+
+  @throws[InterruptedException]
+  override def invokeAll[T <: AnyRef](
+      tasks: util.Collection[_ <: Callable[T]],
+      timeout: Long,
+      unit: TimeUnit
+  ): util.List[Future[T]] = {
+    if (tasks == null || unit == null)
+      throw new NullPointerException()
+    val nanos: Long = unit.toNanos(timeout)
+    val deadline = System.nanoTime() + nanos
+    val futures = new util.ArrayList[Future[T]](tasks.size())
+    var lastIdx = 0
+
+    try {
+      val it = tasks.iterator()
+      while (it.hasNext()) {
+        futures.add(newTaskFor(it.next()))
+      }
+      val size = futures.size()
+
+      // Interleave time checks and calls to execute in case
+      // executor doesn't have any/much parallelism.
+      @tailrec def executeLoop(i: Int): Boolean =
+        if (i >= size) false
+        else {
+          val remainingTime =
+            if (i == 0) nanos
+            else deadline - System.nanoTime()
+          if (remainingTime <= 0) true // timeout
+          else {
+            execute(futures.get(i).asInstanceOf[Runnable])
+            executeLoop(i + 1)
+          }
+        }
+
+      @tailrec def awaitLoop(i: Int): Boolean =
+        if (i >= size) false
+        else {
+          val f = futures.get(i)
+          val timedOut =
+            if (f.isDone()) false
+            else
+              try {
+                f.get(deadline - System.nanoTime(), NANOSECONDS)
+                false
+              } catch {
+                case _: CancellationException | _: ExecutionException => false
+                case _: TimeoutException =>
+                  lastIdx = i
+                  true
+              }
+          if (timedOut) timedOut
+          else awaitLoop(i + 1)
+        }
+
+      val timedOut = executeLoop(0) || awaitLoop(0)
+      if (timedOut) cancelAll(futures, lastIdx)
+    } catch {
+      case t: Throwable =>
+        cancelAll(futures)
+        throw t
+    }
+    futures
+  }
+
+  private def cancelAll[T](futures: util.List[Future[T]], from: Int = 0) =
+    for (i <- from until futures.size()) {
+      futures.get(i).cancel(true)
+    }
+
+}

javalib/src/main/scala/java/util/concurrent/Callable.scala

@@ -1,3 +1,9 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
 package java.util.concurrent
 
 trait Callable[V] {

javalib/src/main/scala/java/util/concurrent/CompletionService.scala

@@ -0,0 +1,21 @@
+/*
+ * Written by Doug Lea with assistance from members of JCP JSR-166
+ * Expert Group and released to the public domain, as explained at
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+package java.util.concurrent
+
+trait CompletionService[V] {
+
+  def submit(task: Callable[V]): Future[V]
+
+  def submit(task: Runnable, result: V): Future[V]
+
+  def take(): Future[V]
+
+  def poll(): Future[V]
+
+  def poll(timeout: Long, unit: TimeUnit): Future[V]
+
+}