code: private void loadJobFile() {
      try {
        String jobFile = getJobFile();
        FileSystem fs = location.getDFS();
        File tmp = File.createTempFile(getJobID().toString(), ".xml");
        if (FileUtil.copy(fs, new Path(jobFile), tmp, false, location
            .getConfiguration())) {
          this.jobConf = new JobConf(tmp.toString());
  
          this.totalMaps = jobConf.getNumMapTasks();
          this.totalReduces = jobConf.getNumReduceTasks();
        }
  
      } catch (IOException ioe) {
        ioe.printStackTrace();
      }
    }
docs: Try to locate and load the JobConf file for this job so to get more
  details on the job (number of maps and of reduces)