Formulas and Evaluation

Writing Formulas

Cell total = row.createCell(2);
total.setCellFormula("B2*1.18"); // 18% tax, for example

FormulaEvaluator eval = wb.getCreationHelper().createFormulaEvaluator();
CellValue v = eval.evaluate(total);
System.out.println("Computed: " + v.getNumberValue());

Notes

• Formulas use English function names with commas (SUM(A1:A10)) regardless of the Excel locale.
• Call evaluator.evaluateAll() before saving if downstream readers expect cached values.
• POI supports most common functions (SUM, IF, VLOOKUP, ...); exotic ones may return #NAME? until Excel recalculates.

Full runnable version: FormulaExample in the poi-examples repo.