@GuardedBy("lock")
  private boolean shutdown = false;

  @Override
  public void execute(Runnable command) {
    startTask();
    try {
      command.run();
    } finally {
      endTask();
    }
  }

  @Override
  public boolean isShutdown() {
    synchronized (lock) {
      return shutdown;
    }
  }

  @Override
  public void shutdown() {
    synchronized (lock) {

        @Override
        public void run() {
          list.execute();
        }
      };

  @Benchmark
  int addThenExecute_multiThreaded(int reps) throws InterruptedException {
    Runnable addTask =
        new Runnable() {
          @Override
          public void run() {
            for (int i = 0; i < numListeners; i++) {
              list.add(listener, directExecutor());
            }
          }

  @GuardedBy("lock")
  private boolean shutdown = false;

  @Override
  public void execute(Runnable command) {
    startTask();
    try {
      command.run();
    } finally {
      endTask();
    }
  }

  @Override
  public boolean isShutdown() {
    synchronized (lock) {
      return shutdown;
    }
  }

  @Override
  public void shutdown() {
    synchronized (lock) {