code: public final void registerTaskExecutor(TaskExecutor taskExecutor) {
  	if (taskExecutor == null) {
  	  throw new TaskExeception(TaskExecutor.class.getSimpleName() + "  NULL");
  	}
  	this.taskExecutor = taskExecutor;
    }
docs: Registers the task executor. DO NOT USE THIS METHOD UNLESS YOU ARE
  DEVELOPING A NEW TASK EXECUTOR.
  
  @param taskExecutor
  the executor