code: public static void setOutputFormat(Class<?> realOutputFormatClass, Configuration conf) {
      conf.setClass("mapred.output.format.class", DeprecatedOutputFormatWrapper.class, org.apache.hadoop.mapred.OutputFormat.class);
      HadoopUtils.setClassConf(conf, CLASS_CONF_KEY, realOutputFormatClass);
    }
docs: For cases where we need to set hadoop1 output format in a hadoop2 Configuration object.