throw new RuntimeException("Thread exited");
        }
        Thread.yield();
      }
    }

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

  static final class TimedWaiterThread extends Thread {
    private final AbstractFuture<?> future;
    private final long timeout;
    private final TimeUnit unit;