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I am trying to merge xlsx sheets from different workbooks to a single workbook. I am able to merge fine but the issue that I am facing is on the styling and formatting which is lost on merge. I have searched on forums, where everyone is suggesting the same that I have in my code snippet below, but for someone unknown reason, the styling doesn't seem to work. Any leads on this will be appreciated.

addSheet(XSSFSheet sheet, XSSFWorkbook wb)

 XSSFSheet sheet2 = wb.createSheet();
 Map<Integer, XSSFCellStyle> styleMap = new HashMap<>();
 for (int j = sheet.getFirstRowNum(); j <= sheet.getLastRowNum(); j++) 

 XSSFRow oldrow = sheet.getRow(j);
 XSSFRow newrow = sheet2.createRow(j);
 for (int k = oldrow.getFirstCellNum(); k < oldrow.getLastCellNum(); k++) 

 XSSFCell oldcell = oldrow.getCell(k);
 XSSFCell newcell = newrow.createCell(k);
 newcell.setCellType(oldcell.getCellType());
 int stHashCode = oldcell.getCellStyle().hashCode();
 XSSFCellStyle newCellStyle = styleMap.get(stHashCode);
 if (newCellStyle == null) 
 newCellStyle = wb.createCellStyle();
 newCellStyle.cloneStyleFrom(oldcell.getCellStyle());
 styleMap.put(stHashCode, newCellStyle);
 
 newcell.setCellStyle(newCellStyle);

 switch (oldcell.getCellType()) 
 case FORMULA:
 newcell.setCellFormula(oldcell.getCellFormula());
 break;
 case NUMERIC:
 newcell.setCellValue(oldcell.getNumericCellValue());
 break;
 case STRING:
 newcell.setCellValue(oldcell.getStringCellValue());
 break;
 case BLANK:
 newcell.setCellType(BLANK);
 break;
 case BOOLEAN:
 newcell.setCellValue(oldcell.getBooleanCellValue());
 break;
 case ERROR:
 newcell.setCellErrorValue(oldcell.getErrorCellValue());
 break;
 default:
 newcell.setCellValue(oldcell.getStringCellValue());
 break;