private void addCell(Record record, Cell cell) throws SAXException {
            if (cell == null) {
                // Ignore empty cells
            } else if (currentSheet != null && record instanceof CellValueRecordInterface) {
                // Normal cell inside a worksheet
                CellValueRecordInterface value = (CellValueRecordInterface) record;
                Point point = new Point(value.getColumn(), value.getRow());
                if (currentSheet.containsKey(point)) {
                    //avoid overwriting content
                    //for now, add to extraTextCells
                    //TODO: consider allowing multiple text pieces
                    //per x,y to keep the text together
                    extraTextCells.add(cell);
                } else {
                    currentSheet.put(point, cell);
                }

            } else {
                // Cell outside the worksheets
                extraTextCells.add(cell);
            }
        }
Adds the given cell (unless <code>null</code>) to the current
worksheet (if any) at the position (if any) of the given record.

@param record record that holds the cell value
@param cell   cell value (or <code>null</code>)
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-microsoft-module/src/main/java/org/apache/tika/parser/microsoft/ExcelExtractor.java