code: public ExcelExporter setColumnsHeader(List<String> columnsHeader) {
  		noOfCols = columnsHeader.size();
  
  		sheet.createFreezePane(0, 1);
  		SXSSFRow headerRow = sheet.createRow(0);
  
  		for (int i = 0; i < columnsHeader.size(); i++) {
  			String cellHeader = columnsHeader.get(i);
  			writeCell(headerRow, i, cellHeader, headerStyle);
  		}
  		return this;
  	}
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