code: public static void addInputPath(JobConf conf, Path path,
        Class<? extends InputFormat> inputFormatClass,
        Class<? extends Mapper> mapperClass) {
  
      addInputPath(conf, path, inputFormatClass);
  
      String mapperMapping = path.toString() + ";" + mapperClass.getName();
      String mappers = conf.get("mapred.input.dir.mappers");
      conf.set("mapred.input.dir.mappers", mappers == null ? mapperMapping
         : mappers + "," + mapperMapping);
  
      conf.setMapperClass(DelegatingMapper.class);
    }
docs: Add a {@link Path} with a custom {@link InputFormat} and
  {@link Mapper} to the list of inputs for the map-reduce job.
  
  @param conf The configuration of the job
  @param path {@link Path} to be added to the list of inputs for the job
  @param inputFormatClass {@link InputFormat} class to use for this path
  @param mapperClass {@link Mapper} class to use for this path