code: public CloseableHttpClient getHttpClient() {
          CloseableHttpClient result = httpClient;
          if (result == null) {
              synchronized (DocumentLoader.class) {
                  result = httpClient;
                  if (result == null) {
                      result = httpClient = JsonUtils.getDefaultHttpClient();
                  }
              }
          }
          return result;
      }
docs: Get the {@link CloseableHttpClient} which will be used by this
  DocumentLoader to resolve HTTP and HTTPS resources.
  
  @return The {@link CloseableHttpClient} which this DocumentLoader uses.