code: public static void setInputFormatClass(Class<?> clazz, Job job) {
      job.setInputFormatClass(MultiInputFormat.class);
      setClassConf(clazz, HadoopCompat.getConfiguration(job));
    }
docs: Sets jobs input format to {@link MultiInputFormat} and stores
  supplied clazz's name in job configuration. This configuration is
  read on the remote tasks to initialize the input format correctly.