How to insert a row between two rows in an existing excel with HSSF (Apache POI)

Question

Somehow I manage to create new rows between two rows in an existing excel file. The problem is, some of the formatting were not include along the shifting of the rows.

Answer 1

I merged some of the other answers and comments in the following implementation, tested with Apache POI v3.9.

I have only one rownum parameter because I shift down the target row and copy it in the new empty row. Formulas are handled as expected, they are not copied verbatim, with one exception: references to cells that are above the copied line are not updated; the workaround is to replace these explicit references (if any) with references calculated using INDIRECT() as suggested by this post.

protected void copyRow(Sheet worksheet, int rowNum) {
    Row sourceRow = worksheet.getRow(rowNum);

    //Save the text of any formula before they are altered by row shifting
    String[] formulasArray = new String[sourceRow.getLastCellNum()];
    for (int i = 0; i < sourceRow.getLastCellNum(); i++) {
        if (sourceRow.getCell(i) != null && sourceRow.getCell(i).getCellType() == Cell.CELL_TYPE_FORMULA) 
            formulasArray[i] = sourceRow.getCell(i).getCellFormula();
    }

    worksheet.shiftRows(rowNum, worksheet.getLastRowNum(), 1);
    Row newRow = sourceRow;  //Now sourceRow is the empty line, so let's rename it
    sourceRow = worksheet.getRow(rowNum + 1);  //Now the source row is at rowNum+1

    // Loop through source columns to add to new row
    for (int i = 0; i < sourceRow.getLastCellNum(); i++) {
        // Grab a copy of the old/new cell
        Cell oldCell = sourceRow.getCell(i);
        Cell newCell;

        // If the old cell is null jump to next cell
        if (oldCell == null) {
            continue;
        } else {
            newCell = newRow.createCell(i);
        }

        // Copy style from old cell and apply to new cell
        CellStyle newCellStyle = worksheet.getWorkbook().createCellStyle();
        newCellStyle.cloneStyleFrom(oldCell.getCellStyle());
        newCell.setCellStyle(newCellStyle);

        // If there is a cell comment, copy
        if (oldCell.getCellComment() != null) {
            newCell.setCellComment(oldCell.getCellComment());
        }

        // If there is a cell hyperlink, copy
        if (oldCell.getHyperlink() != null) {
            newCell.setHyperlink(oldCell.getHyperlink());
        }

        // Set the cell data type
        newCell.setCellType(oldCell.getCellType());

        // Set the cell data value
        switch (oldCell.getCellType()) {
            case Cell.CELL_TYPE_BLANK:
                break;
            case Cell.CELL_TYPE_BOOLEAN:
                newCell.setCellValue(oldCell.getBooleanCellValue());
                break;
            case Cell.CELL_TYPE_ERROR:
                newCell.setCellErrorValue(oldCell.getErrorCellValue());
                break;
            case Cell.CELL_TYPE_FORMULA:
                newCell.setCellFormula(formulasArray[i]);
                break;
            case Cell.CELL_TYPE_NUMERIC:
                newCell.setCellValue(oldCell.getNumericCellValue());
                break;
            case Cell.CELL_TYPE_STRING:
                newCell.setCellValue(oldCell.getRichStringCellValue());
                break;
            default:   
                break; 
        }
    }

    // If there are any merged regions in the source row, copy to new row
    for (int i = 0; i < worksheet.getNumMergedRegions(); i++) {
        CellRangeAddress cellRangeAddress = worksheet.getMergedRegion(i);
        if (cellRangeAddress.getFirstRow() == sourceRow.getRowNum()) {
            CellRangeAddress newCellRangeAddress = new CellRangeAddress(newRow.getRowNum(),
                    (newRow.getRowNum() +
                            (cellRangeAddress.getLastRow() - cellRangeAddress.getFirstRow()
                                    )),
                    cellRangeAddress.getFirstColumn(),
                    cellRangeAddress.getLastColumn());
            worksheet.addMergedRegion(newCellRangeAddress);
        }
    }
}

I'm using this implementation in production code.