void awaitWaiting() {
      while (!isBlocked()) {
        if (getState() == State.TERMINATED) {
          throw new RuntimeException("Thread exited");
        }
        Thread.yield();
      }
    }

    private boolean isBlocked() {
      return getState() == Thread.State.WAITING && LockSupport.getBlocker(this) == future;
    }
  }

    void awaitWaiting() {
      while (!isBlocked()) {
        if (getState() == State.TERMINATED) {
          throw new RuntimeException("Thread exited");
        }
        Thread.yield();
      }
    }

    private boolean isBlocked() {
      return getState() == Thread.State.WAITING && LockSupport.getBlocker(this) == future;
    }
  }

 * existing users, but it can't *fix* existing users because any users who needed
 * `Function<@Nullable A, @Nullable B>` already had to find a workaround. Still, there is a *ton* of
 * fallout from trying to switch. I would be shocked if the switch would offer benefits to anywhere
 * near enough users to justify the costs.
 *
 * Fortunately, if anyone does want to use a Converter as a `Function<@Nullable A, @Nullable B>`,