code: public static <T extends ExecutorService> T requireNotShutdown(final T executorService) {
  	if (executorService.isShutdown()) {
  	    throw new IllegalArgumentException("ExecutorService is shutdown");
  	}
  	return executorService;
      }
docs: Validates the supplied service is not shutdown.
  
  @param executorService
  Service to check.
  @return The service.