@Override
  public T get() throws InterruptedException, ExecutionException {
    try {
      return get(1, TimeUnit.SECONDS);
    } catch (TimeoutException ex) {
      return null;
    }
  }
A very basic {@link ListenableFuture} to verify and test basic
add, remove and notification behavior.
src/test/java/net/spy/memcached/internal/DummyListenableFuture.java