code: public int getNormalizedColumn(int line, int column) {
          int deltaLine = line - firstLine;
          if (deltaLine < 0 || deltaLine >= lineOffsets.size()) // wrong line information
              return -1;
          int deltaColumn = column - lineOffsets.get(deltaLine);
          if (deltaColumn < 0) // wrong column information
              return -1;
  
          return textOffsets.get(deltaLine) + deltaColumn;
      }
docs: Returns the column in <tt>getNormalizedText()</tt> corresponding
  to the given line and column in the original source text. The
  first character in the normalized text has column 1.
  
  @param line   a line number
  @param column a column number
  @return the column in getNormalizedText() corresponding to the given line
  and column in the original source text