Merge and align center cell using apache poi

Question

I want to export data to excel using Apache poi.
Now the problem that I am facing is that I am unable to merge rows and align them in the center.

Code for export data is:

List<LinkedHashMap<String,Object>> lstReportHeader = null;
HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet = wb.createSheet();

//Set Header Font
HSSFFont headerFont = wb.createFont();
headerFont.setBoldweight(headerFont.BOLDWEIGHT_BOLD);
headerFont.setFontHeightInPoints((short) 12);

//Set Header Style
CellStyle headerStyle = wb.createCellStyle();
headerStyle.setFillBackgroundColor(IndexedColors.BLACK.getIndex());
headerStyle.setAlignment(headerStyle.ALIGN_CENTER);
headerStyle.setFont(headerFont);
headerStyle.setBorderBottom(HSSFCellStyle.BORDER_MEDIUM);
int rowCount= 0;
Row header;
header = sheet.createRow(0);//its for header 
Cell cell ;//= header.createCell(0);
for(int j = 0;j < 4; j++) {
    cell = header.createCell(j);
    if(j == 0) {
        cell.setCellValue("ItemWise List");
    }
    cell.setCellStyle(headerStyle);
}
sheet.addMergedRegion(new CellRangeAddress(rowCount, rowCount, 0, lstReportFormHeader.size()-1));
header = sheet.createRow(0);
        cell = header.createCell(0);
cell.setCellValue("Sr. No");
        cell = header.createCell(1);
cell.setCellValue("Item Name");
        cell = header.createCell(2);
cell.setCellValue("Qty");
        cell = header.createCell(3);
cell.setCellValue("Rate");

Now I want to ItemWise List merge and make it align center.

Answer 1

My solution was to merge the cells by their positions, then created a cell (reference to the first block of the merged cells) to assign a value and then set the alignment throught the CellUtil

// Merges the cells
CellRangeAddress cellRangeAddress = new CellRangeAddress(start, start, j, j + 1);
sheet.addMergedRegion(cellRangeAddress);

// Creates the cell
Cell cell = CellUtil.createCell(row, j, entry.getKey());

// Sets the allignment to the created cell
CellUtil.setAlignment(cell, workbook, CellStyle.ALIGN_CENTER);