code: private void fillNextLine() {
          try {
              while (nextLine == null && !eof) {
                  String line = reader.readLine();
                  if (line == null) {
                      eof = true;
                      reader.close();
                  } else if (isBlank(line)) {
                      continue;
                  } else if (isComment(line)) {
                      continue;
                  } else {
                      nextLine = line;
                  }
              }
          } catch (IOException e) {
              throw new IllegalStateException(e);
          }
      }
docs: Scan through the file until we get an EOF or a good line.