code: private void printErrLine(int pos, PrintWriter writer) {
          String line = (source == null ? null : source.getLine(pos));
          if (line == null)
              return;
          int col = source.getColumnNumber(pos, false);
  
          printRawLines(writer, line);
          for (int i = 0; i < col - 1; i++) {
              writer.print((line.charAt(i) == '\t') ? "\t" : " ");
          }
          writer.println("^");
          writer.flush();
      }
docs: Print the faulty source code line and point to the error.
  @param pos   Buffer index of the error position, must be on current line