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 tried this working fine...

HSSFCellStyle cellStyle = wb.createCellStyle();
HSSFDataFormat hssfDataFormat = wb.createDataFormat(); 
String cellVal = "2500";
cellStyle.setDataFormat(hssfDataFormat.getFormat("#,##0.000"));
newCell.setCellStyle(cellStyle);
newCell.setCellValue(new Double(cellVal));
newCell.setCellType(Cell.CELL_TYPE_NUMERIC);

The output is a numeric value with desired format: 2,500.000

Answer 2

Do you need to put both values in one cell? Can you split them up into 2 columns? Excel has a built-in "Texts to Columns" function that you should be able to reference that will split an entire column of text strings into multiple columns based on a delimiter (like a comma). In VBA, it looks something like this:

Selection.TextToColumns Destination:=Range("A1"), DataType:=xlDelimited, _
TextQualifier:=xlDoubleQuote, ConsecutiveDelimiter:=False, Tab:=False, _
Semicolon:=False, Comma:=True, Space:=False, Other:=False, FieldInfo _
:=Array(Array(1, 1), Array(2, 1)), TrailingMinusNumbers:=True

As for your first proposed solution, it is not possible to force Excel to treat something as a number if it is not convertable to a number.

Answer 3

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