cells = new HashMap<Long, Cell>();
merges = new LinkedList<MergeBlock>();
cellPool = new CellPool();
rowPool = new RowPool();
columnPool = new ColumnPool();
defaultCell = CellImpl.create(null, getStyle());
defaultRow = RowImpl.create(getStyle());
defaultRow.setHeight(10);
defaultColumn = ColumnImpl.create(getStyle());