// Create a new workbook Workbook workbook = new Workbook(); IWorksheet worksheet = workbook.getWorksheets().get(0); // Set range values. worksheet.getRange("A2:B2").setValue(-15.50); worksheet.getRange("A3:B3").setValue(555); worksheet.getRange("A4:B4").setValue(0); worksheet.getRange("A5:B5").setValue("Name"); // Apply custom number format. worksheet.getRange("B2:B5").setNumberFormat("[Green]#.00;[Red]#.00;[Blue]0.00;[Cyan]\"product: \"@"); // Save to an excel file workbook.save("CustomNumberFormat.xlsx");