code: public BufferedReader open(String fileName) throws IOException {
          Path filePath = new Path(fileName);
          
          if (!hadoopFs.exists(filePath)) {
              throw new IOException(fileName + " does not exist in HDFS");
          }
  
          BufferedReader br = new BufferedReader(new InputStreamReader(
              hadoopFs.open(filePath)));
          return br;
      }
docs: Finds the file with the specified name and returns a reader for that
  files contents.
  
  @param fileName the name of a file
  
  @return a {@code BufferedReader} to the contents of the specified file
  
  @throws IOException if the resource cannot be found or if an error occurs
  while opening the resource