code: public HDFSDistributor setOutputFileDir(String fileName) {
          this.mapperOutputFileName = fileName;
          if (hdfsFileRoot != null) {
              this.mapperOutputFilePath = new Path(hdfsFileRoot + "/" + mapperOutputFileName);
          }
          return this;
      }
docs: Set the output file directory (to be appended to hdfsFileRoot)
  
  @param fileName Path from hdfsFileRoot
  @return an updated HDFSDistributor with output file name set