Write Double value in numeric cell with specific format in Apache Poi 3.7

Question

I need to write a Double value in a numeric cell using a specific format, i mean, the generated xls must have numeric cells containing Double values like, for example: 8,1.

Answer 1

I may be missing something, but I think you just want to style the cell with a format rule to display a single decimal place

// Do this only once per file
CellStyle cellStyle = wb.createCellStyle();
cellStyle.setDataFormat(
    wb.getCreationHelper().createDataFormat().getFormat("#.#"));

// Create the cell
Cell c = row.createCell(2);
c.setCellValue(8.1);
c.setCellStyle(cellStyle);

That will create a formatting rule, create a cell, set the cell to be the value 8.1, then style it