How to transpose sheet with POI SS/XSSF? - excel

Question

I am using POI XSSF API and I would like to transpose a sheet.
how can I do that?
Thanks.

Answer 1

Transpose, as in swap A2 with B1 and A3 with C1 (so columns become rows)?
If so, there's nothing built in, so you'd need to do a little bit of coding yourself. You'd likely want to grab a pair of cells, save the contents of one (value and style), copy the second to the first, then overwrite the second.
See the quick guide if you're not sure on all the reading/writing parts.

Answer 2

I was looking for the same answer and had to code it myself. I've attached my solution which is quite simple:
Determine the number of rows
Determine the maximal number of columns used
Iterator over every row, and every column
Save the Cell from that row/column into a simple list as a 'CellModel' type
Once done, iterate over all CellModels
Switch column and row index and save the CellModel into the sheet
The code I've used is:
public static void transpose(Workbook wb, int sheetNum, boolean replaceOriginalSheet) {
Sheet sheet = wb.getSheetAt(sheetNum);
Pair<Integer, Integer> lastRowColumn = getLastRowAndLastColumn(sheet);
int lastRow = lastRowColumn.getFirst();
int lastColumn = lastRowColumn.getSecond();
LOG.debug("Sheet {} has {} rows and {} columns, transposing ...", new Object[] {sheet.getSheetName(), 1+lastRow, lastColumn});
List<CellModel> allCells = new ArrayList<CellModel>();
for (int rowNum = 0; rowNum <= lastRow; rowNum++) {
Row row = sheet.getRow(rowNum);
if (row == null) {
continue;
}
for (int columnNum = 0; columnNum < lastColumn; columnNum++) {
Cell cell = row.getCell(columnNum);
allCells.add(new CellModel(cell));
}
}
LOG.debug("Read {} cells ... transposing them", allCells.size());
Sheet tSheet = wb.createSheet(sheet.getSheetName() + "_transposed");
for (CellModel cm : allCells) {
if (cm.isBlank()) {
continue;
}
int tRow = cm.getColNum();
int tColumn = cm.getRowNum();
Row row = tSheet.getRow(tRow);
if (row == null) {
row = tSheet.createRow(tRow);
}
Cell cell = row.createCell(tColumn);
cm.insertInto(cell);
}
lastRowColumn = getLastRowAndLastColumn(sheet);
lastRow = lastRowColumn.getFirst();
lastColumn = lastRowColumn.getSecond();
LOG.debug("Transposing done. {} now has {} rows and {} columns.", new Object[] {tSheet.getSheetName(), 1+lastRow, lastColumn});
if (replaceOriginalSheet) {
int pos = wb.getSheetIndex(sheet);
wb.removeSheetAt(pos);
wb.setSheetOrder(tSheet.getSheetName(), pos);
}
}
private static Pair<Integer, Integer> getLastRowAndLastColumn(Sheet sheet) {
int lastRow = sheet.getLastRowNum();
int lastColumn = 0;
for (Row row : sheet) {
if (lastColumn < row.getLastCellNum()) {
lastColumn = row.getLastCellNum();
}
}
return new Pair<Integer, Integer>(lastRow, lastColumn);
}
Whereby the CellModel is a wrapper which holds the data a Cell contained (you can add more attributes if you like e.g., comments, ...):
static class CellModel {
private int rowNum = -1;
private int colNum = -1;
private CellStyle cellStyle;
private int cellType = -1;
private Object cellValue;
public CellModel(Cell cell) {
if (cell != null) {
this.rowNum = cell.getRowIndex();
this.colNum = cell.getColumnIndex();
this.cellStyle = cell.getCellStyle();
this.cellType = cell.getCellType();
switch (this.cellType) {
case Cell.CELL_TYPE_BLANK:
break;
case Cell.CELL_TYPE_BOOLEAN:
cellValue = cell.getBooleanCellValue();
break;
case Cell.CELL_TYPE_ERROR:
cellValue = cell.getErrorCellValue();
break;
case Cell.CELL_TYPE_FORMULA:
cellValue = cell.getCellFormula();
break;
case Cell.CELL_TYPE_NUMERIC:
cellValue = cell.getNumericCellValue();
break;
case Cell.CELL_TYPE_STRING:
cellValue = cell.getRichStringCellValue();
break;
}
}
}
public boolean isBlank() {
return this.cellType == -1 && this.rowNum == -1 && this.colNum == -1;
}
public void insertInto(Cell cell) {
if (isBlank()) {
return;
}
cell.setCellStyle(this.cellStyle);
cell.setCellType(this.cellType);
switch (this.cellType) {
case Cell.CELL_TYPE_BLANK:
break;
case Cell.CELL_TYPE_BOOLEAN:
cell.setCellValue((boolean) this.cellValue);
break;
case Cell.CELL_TYPE_ERROR:
cell.setCellErrorValue((byte) this.cellValue);
break;
case Cell.CELL_TYPE_FORMULA:
cell.setCellFormula((String) this.cellValue);
break;
case Cell.CELL_TYPE_NUMERIC:
cell.setCellValue((double) this.cellValue);
break;
case Cell.CELL_TYPE_STRING:
cell.setCellValue((RichTextString) this.cellValue);
break;
}
}
public CellStyle getCellStyle() {
return cellStyle;
}
public int getCellType() {
return cellType;
}
public Object getCellValue() {
return cellValue;
}
public int getRowNum() {
return rowNum;
}
public int getColNum() {
return colNum;
}
}