return optional.isPresent() ? DoubleStream.of(optional.getAsDouble()) : DoubleStream.empty();
  }

  @SuppressWarnings("CatchingUnchecked") // sneaky checked exception
  private static void closeAll(BaseStream<?, ?>[] toClose) {
    // If one of the streams throws an exception, continue closing the others, then throw the
    // exception later. If more than one stream throws an exception, the later ones are added to the

Upgrading to OkHttp 4
=====================

OkHttp 4.x upgrades our implementation language from Java to Kotlin and keeps everything else the
same. We’ve chosen Kotlin because it gives us powerful new capabilities while integrating closely
with Java.

We spent a lot of time and energy on retaining strict compatibility with OkHttp 3.x. We’re even
keeping the package name the same: `okhttp3`!

There are three kinds of compatibility we’re tracking:

   * we've chosen to instead use a signature that benefits existing users -- and is still safe.
   *
   * For convertAll, I haven't looked as closely at *how* much existing users benefit, so we should
   * keep an eye out for problems that new users encounter. Note also that convertAll could support