code: public synchronized boolean next(Text key, Text value) throws IOException {
      Text tKey = key;
      Text tValue = value;
      if (!sequenceFileRecordReader.next(innerKey, innerValue)) {
        return false;
      }
      tKey.set(innerKey.toString());
      tValue.set(innerValue.toString());
      return true;
    }
docs: Read key/value pair in a line.