* is complete. It does so by using daemon threads and adding a shutdown hook to wait for their
   * completion.
   *
   * <p>This is mainly for fixed thread pools. See {@link Executors#newFixedThreadPool(int)}.
   *
   * @param executor the executor to modify to make sure it exits when the application is finished
   * @param terminationTimeout how long to wait for the executor to finish before terminating the
   *     JVM

  //      */
  //     public void await(AtomicBoolean flag) {
  //         await(flag, LONG_DELAY_MS);
  //     }

  //     /**
  //      * Spin-waits up to the specified timeout until flag becomes true.
  //      */
  //     public void await(AtomicBoolean flag, long timeoutMillis) {
  //         long startTime = System.nanoTime();
  //         while (!flag.get()) {

   * numElements} elements are not available, it will wait for them up to the specified timeout.
   *
   * @param q the blocking queue to be drained
   * @param buffer where to add the transferred elements
   * @param numElements the number of elements to be waited for
   * @param timeout how long to wait before giving up, in units of {@code unit}

  //      */
  //     public void await(AtomicBoolean flag) {
  //         await(flag, LONG_DELAY_MS);
  //     }

  //     /**
  //      * Spin-waits up to the specified timeout until flag becomes true.
  //      */
  //     public void await(AtomicBoolean flag, long timeoutMillis) {
  //         long startTime = System.nanoTime();
  //         while (!flag.get()) {

              if (remainingNanos < SPIN_THRESHOLD_NANOS) {
                // Remove the waiter, one way or another we are done parking this thread.
                removeWaiter(node);
                break long_wait_loop; // jump down to the busy wait loop
              }
            }
          }
          oldHead = waiters; // re-read and loop.
        } while (oldHead != Waiter.TOMBSTONE);
      }

          @Override
          public ListenableFuture<String> call() throws Exception {
            inFunction.countDown();
            try {
              new CountDownLatch(1).await(); // wait for interrupt
            } catch (InterruptedException expected) {
              gotException.countDown();
              throw expected;
            }
            return immediateFuture("a");
          }

          @Override
          public ListenableFuture<String> call() throws Exception {
            inFunction.countDown();
            try {
              new CountDownLatch(1).await(); // wait for interrupt
            } catch (InterruptedException expected) {
              gotException.countDown();
              throw expected;
            }
            return immediateFuture("a");
          }

          }
        } else {
          // In the case of a concurrent remove, we might observe a zero value, which means another
          // thread is about to remove (element, existingCounter) from the map. Rather than wait,
          // we can just do that work here.
          AtomicInteger newCounter = new AtomicInteger(occurrences);
          if ((countMap.putIfAbsent(element, newCounter) == null)

          }
        } else {
          // In the case of a concurrent remove, we might observe a zero value, which means another
          // thread is about to remove (element, existingCounter) from the map. Rather than wait,
          // we can just do that work here.
          AtomicInteger newCounter = new AtomicInteger(occurrences);
          if ((countMap.putIfAbsent(element, newCounter) == null)

            return loadSync(key, hash, loadingValueReference, loader);
          }
        } finally {
          statsCounter.recordMisses(1);
        }
      } else {
        // The entry already exists. Wait for loading.
        return waitForLoadingValue(e, key, valueReference);
      }
    }

    V waitForLoadingValue(ReferenceEntry<K, V> e, K key, ValueReference<K, V> valueReference)