Reading result of Formula Cells in Apache POI 3.15 - scala

Question

I try to read the values from a cell as a String (as one would see it in Excel). I reads from a xlsx (XSSFWorkbook) using Apache POI 3.15.
My goal is e.g. to omit decimal point and trailing zeros if the cell contains an integer. This works for CellType.NUMERIC:
val dataFormatter = new DataFormatter(true) // set emulateCsv to true
val stringValue = dataFormatter.formatCellValue(cell)
If I use the same code for CellType.FORMULA cell (e.g. a cell which references another "integer" cell), it just gives me the formula as a string instead of its computed value.
How can I get value of the formula-cell as displayed in Excel displays?

Answer 1

You need to "evaluate" cells in order to get the result of formulas. This is not done automatically by POI as it can be a heavy operation and often will not be necessary.
See http://poi.apache.org/spreadsheet/eval.html for details, basically you create a FormulaEvaluator and retrieve a CellValue for the Cell in question
FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
...
CellValue cellValue = evaluator.evaluate(cell);

Answer 2

Thanks to Centic and Raphael I ended up using the concept with NumberFormat to fix an issue, this is Java but I am sure it can easily be converted to Scala
The issue is around numbers with decimal places which produces scientific decimal points.
This was only required when converting Apache POI XLS / XLSX to CSV format
//Create an evaluator from current work book
FormulaEvaluator evaluator = wb.getCreationHelper().createFormulaEvaluator();
// Cell cell2 = evaluator.evaluateInCell(cell);
// As per above get CellValue
CellValue cellValue = evaluator.evaluate(cell);
//Get Double Value of formula which may contain E numbers
Double value = cellValue.getNumberValue();
// This gets numberFormat (below function) and assigns correct formatting to it
NumberFormat formatter = getNumberFormat(value);
//This should now be string value of number with correct decimal place values (non scientific)
formatter.format(value)
/**
* getNumberFormat takes number and either assigns #0
* if no decimal places or
* depending on how many numbers after decimal place assigns correct format
*/
public static NumberFormat getNumberFormat(Double value) {
String v = value.toString();
String format = "#0";
// This fixes scientific value issue
if (v.contains(".")) {
int decimals = v).substring(v.indexOf(".") + 1).length();
//Calls generateNumberSigns based on decimal places in given double
String numberSigns = generateNumberSigns(decimals);
format = "0." + numberSigns;
}
return new DecimalFormat(format);
}
/**
* This will generate correct formula for amount of decimal places
*/
public static String generateNumberSigns(int n) {
String s = "";
for (int i = 0; i < n; i++) {
s += "#";
}
return s;
}