I think you may use addCalculatedField method of PivotTable to implement your desired formula, see the sample code below/ I have written an example for your reference. This example just gives you an idea on how to accomplish the task, you may write your own code and formula accordingly for your needs based on your source data range.
//Instantiating an Workbook object
Workbook workbook = new Workbook();
//Obtaining the reference of the first worksheet
Worksheet sheet = workbook.getWorksheets().get(0);
//Name the sheet
sheet.setName(“Data”);
Cells cells = sheet.getCells();
//Setting the values to the cells
Cell cell = cells.get(“A1”);
cell.setValue(“Employee”);
cell = cells.get(“B1”);
cell.setValue(“Quarter”);
cell = cells.get(“C1”);
cell.setValue(“Product”);
cell = cells.get(“D1”);
cell.setValue(“Continent”);
cell = cells.get(“E1”);
cell.setValue(“Country”);
cell = cells.get(“F1”);
cell.setValue(“Sale”);
cell = cells.get(“A2”);
cell.setValue(“David”);
cell = cells.get(“A3”);
cell.setValue(“David”);
cell = cells.get(“A4”);
cell.setValue(“David”);
cell = cells.get(“A5”);
cell.setValue(“David”);
cell = cells.get(“A6”);
cell.setValue(“James”);
cell = cells.get(“A7”);
cell.setValue(“James”);
cell = cells.get(“A8”);
cell.setValue(“James”);
cell = cells.get(“A9”);
cell.setValue(“James”);
cell = cells.get(“A10”);
cell.setValue(“James”);
cell = cells.get(“A11”);
cell.setValue(“Miya”);
cell = cells.get(“A12”);
cell.setValue(“Miya”);
cell = cells.get(“A13”);
cell.setValue(“Miya”);
cell = cells.get(“A14”);
cell.setValue(“Miya”);
cell = cells.get(“A15”);
cell.setValue(“Miya”);
cell = cells.get(“A16”);
cell.setValue(“Miya”);
cell = cells.get(“A17”);
cell.setValue(“Miya”);
cell = cells.get(“A18”);
cell.setValue(“Elvis”);
cell = cells.get(“A19”);
cell.setValue(“Elvis”);
cell = cells.get(“A20”);
cell.setValue(“Elvis”);
cell = cells.get(“A21”);
cell.setValue(“Elvis”);
cell = cells.get(“A22”);
cell.setValue(“Elvis”);
cell = cells.get(“A23”);
cell.setValue(“Elvis”);
cell = cells.get(“A24”);
cell.setValue(“Elvis”);
cell = cells.get(“A25”);
cell.setValue(“Jean”);
cell = cells.get(“A26”);
cell.setValue(“Jean”);
cell = cells.get(“A27”);
cell.setValue(“Jean”);
cell = cells.get(“A28”);
cell.setValue(“Ada”);
cell = cells.get(“A29”);
cell.setValue(“Ada”);
cell = cells.get(“A30”);
cell.setValue(“Ada”);
cell = cells.get(“B2”);
cell.setValue(“1”);
cell = cells.get(“B3”);
cell.setValue(“2”);
cell = cells.get(“B4”);
cell.setValue(“3”);
cell = cells.get(“B5”);
cell.setValue(“4”);
cell = cells.get(“B6”);
cell.setValue(“1”);
cell = cells.get(“B7”);
cell.setValue(“2”);
cell = cells.get(“B8”);
cell.setValue(“3”);
cell = cells.get(“B9”);
cell.setValue(“4”);
cell = cells.get(“B10”);
cell.setValue(“4”);
cell = cells.get(“B11”);
cell.setValue(“1”);
cell = cells.get(“B12”);
cell.setValue(“1”);
cell = cells.get(“B13”);
cell.setValue(“2”);
cell = cells.get(“B14”);
cell.setValue(“2”);
cell = cells.get(“B15”);
cell.setValue(“3”);
cell = cells.get(“B16”);
cell.setValue(“4”);
cell = cells.get(“B17”);
cell.setValue(“4”);
cell = cells.get(“B18”);
cell.setValue(“1”);
cell = cells.get(“B19”);
cell.setValue(“1”);
cell = cells.get(“B20”);
cell.setValue(“2”);
cell = cells.get(“B21”);
cell.setValue(“3”);
cell = cells.get(“B22”);
cell.setValue(“3”);
cell = cells.get(“B23”);
cell.setValue(“4”);
cell = cells.get(“B24”);
cell.setValue(“4”);
cell = cells.get(“B25”);
cell.setValue(“1”);
cell = cells.get(“B26”);
cell.setValue(“2”);
cell = cells.get(“B27”);
cell.setValue(“3”);
cell = cells.get(“B28”);
cell.setValue(“1”);
cell = cells.get(“B29”);
cell.setValue(“2”);
cell = cells.get(“B30”);
cell.setValue(“3”);
cell = cells.get(“C2”);
cell.setValue(“Maxilaku”);
cell = cells.get(“C3”);
cell.setValue(“Maxilaku”);
cell = cells.get(“C4”);
cell.setValue(“Chai”);
cell = cells.get(“C5”);
cell.setValue(“Maxilaku”);
cell = cells.get(“C6”);
cell.setValue(“Chang”);
cell = cells.get(“C7”);
cell.setValue(“Chang”);
cell = cells.get(“C8”);
cell.setValue(“Chang”);
cell = cells.get(“C9”);
cell.setValue(“Chang”);
cell = cells.get(“C10”);
cell.setValue(“Chang”);
cell = cells.get(“C11”);
cell.setValue(“Geitost”);
cell = cells.get(“C12”);
cell.setValue(“Chai”);
cell = cells.get(“C13”);
cell.setValue(“Geitost”);
cell = cells.get(“C14”);
cell.setValue(“Geitost”);
cell = cells.get(“C15”);
cell.setValue(“Maxilaku”);
cell = cells.get(“C16”);
cell.setValue(“Geitost”);
cell = cells.get(“C17”);
cell.setValue(“Geitost”);
cell = cells.get(“C18”);
cell.setValue(“Ikuru”);
cell = cells.get(“C19”);
cell.setValue(“Ikuru”);
cell = cells.get(“C20”);
cell.setValue(“Ikuru”);
cell = cells.get(“C21”);
cell.setValue(“Ikuru”);
cell = cells.get(“C22”);
cell.setValue(“Ipoh Coffee”);
cell = cells.get(“C23”);
cell.setValue(“Ipoh Coffee”);
cell = cells.get(“C24”);
cell.setValue(“Ipoh Coffee”);
cell = cells.get(“C25”);
cell.setValue(“Chocolade”);
cell = cells.get(“C26”);
cell.setValue(“Chocolade”);
cell = cells.get(“C27”);
cell.setValue(“Chocolade”);
cell = cells.get(“C28”);
cell.setValue(“Chocolade”);
cell = cells.get(“C29”);
cell.setValue(“Chocolade”);
cell = cells.get(“C30”);
cell.setValue(“Chocolade”);
cell = cells.get(“D2”);
cell.setValue(“Asia”);
cell = cells.get(“D3”);
cell.setValue(“Asia”);
cell = cells.get(“D4”);
cell.setValue(“Asia”);
cell = cells.get(“D5”);
cell.setValue(“Asia”);
cell = cells.get(“D6”);
cell.setValue(“Europe”);
cell = cells.get(“D7”);
cell.setValue(“Europe”);
cell = cells.get(“D8”);
cell.setValue(“Europe”);
cell = cells.get(“D9”);
cell.setValue(“Europe”);
cell = cells.get(“D10”);
cell.setValue(“Europe”);
cell = cells.get(“D11”);
cell.setValue(“America”);
cell = cells.get(“D12”);
cell.setValue(“America”);
cell = cells.get(“D13”);
cell.setValue(“America”);
cell = cells.get(“D14”);
cell.setValue(“America”);
cell = cells.get(“D15”);
cell.setValue(“America”);
cell = cells.get(“D16”);
cell.setValue(“America”);
cell = cells.get(“D17”);
cell.setValue(“America”);
cell = cells.get(“D18”);
cell.setValue(“Europe”);
cell = cells.get(“D19”);
cell.setValue(“Europe”);
cell = cells.get(“D20”);
cell.setValue(“Europe”);
cell = cells.get(“D21”);
cell.setValue(“Oceania”);
cell = cells.get(“D22”);
cell.setValue(“Oceania”);
cell = cells.get(“D23”);
cell.setValue(“Oceania”);
cell = cells.get(“D24”);
cell.setValue(“Oceania”);
cell = cells.get(“D25”);
cell.setValue(“Africa”);
cell = cells.get(“D26”);
cell.setValue(“Africa”);
cell = cells.get(“D27”);
cell.setValue(“Africa”);
cell = cells.get(“D28”);
cell.setValue(“Africa”);
cell = cells.get(“D29”);
cell.setValue(“Africa”);
cell = cells.get(“D30”);
cell.setValue(“Africa”);
cell = cells.get(“E2”);
cell.setValue(“China”);
cell = cells.get(“E3”);
cell.setValue(“India”);
cell = cells.get(“E4”);
cell.setValue(“Korea”);
cell = cells.get(“E5”);
cell.setValue(“India”);
cell = cells.get(“E6”);
cell.setValue(“France”);
cell = cells.get(“E7”);
cell.setValue(“France”);
cell = cells.get(“E8”);
cell.setValue(“Germany”);
cell = cells.get(“E9”);
cell.setValue(“Italy”);
cell = cells.get(“E10”);
cell.setValue(“France”);
cell = cells.get(“E11”);
cell.setValue(“U.S.”);
cell = cells.get(“E12”);
cell.setValue(“U.S.”);
cell = cells.get(“E13”);
cell.setValue(“Brazil”);
cell = cells.get(“E14”);
cell.setValue(“U.S.”);
cell = cells.get(“E15”);
cell.setValue(“U.S.”);
cell = cells.get(“E16”);
cell.setValue(“Canada”);
cell = cells.get(“E17”);
cell.setValue(“U.S.”);
cell = cells.get(“E18”);
cell.setValue(“Italy”);
cell = cells.get(“E19”);
cell.setValue(“France”);
cell = cells.get(“E20”);
cell.setValue(“Italy”);
cell = cells.get(“E21”);
cell.setValue(“New Zealand”);
cell = cells.get(“E22”);
cell.setValue(“Australia”);
cell = cells.get(“E23”);
cell.setValue(“Australia”);
cell = cells.get(“E24”);
cell.setValue(“New Zealand”);
cell = cells.get(“E25”);
cell.setValue(“S.Africa”);
cell = cells.get(“E26”);
cell.setValue(“S.Africa”);
cell = cells.get(“E27”);
cell.setValue(“S.Africa”);
cell = cells.get(“E28”);
cell.setValue(“Egypt”);
cell = cells.get(“E29”);
cell.setValue(“Egypt”);
cell = cells.get(“E30”);
cell.setValue(“Egypt”);
cell = cells.get(“F2”);
cell.setValue(2000);
cell = cells.get(“F3”);
cell.setValue(500);
cell = cells.get(“F4”);
cell.setValue(1200);
cell = cells.get(“F5”);
cell.setValue(1500);
cell = cells.get(“F6”);
cell.setValue(500);
cell = cells.get(“F7”);
cell.setValue(1500);
cell = cells.get(“F8”);
cell.setValue(800);
cell = cells.get(“F9”);
cell.setValue(900);
cell = cells.get(“F10”);
cell.setValue(500);
cell = cells.get(“F11”);
cell.setValue(1600);
cell = cells.get(“F12”);
cell.setValue(600);
cell = cells.get(“F13”);
cell.setValue(2000);
cell = cells.get(“F14”);
cell.setValue(500);
cell = cells.get(“F15”);
cell.setValue(900);
cell = cells.get(“F16”);
cell.setValue(700);
cell = cells.get(“F17”);
cell.setValue(1400);
cell = cells.get(“F18”);
cell.setValue(1350);
cell = cells.get(“F19”);
cell.setValue(300);
cell = cells.get(“F20”);
cell.setValue(500);
cell = cells.get(“F21”);
cell.setValue(1000);
cell = cells.get(“F22”);
cell.setValue(1500);
cell = cells.get(“F23”);
cell.setValue(1500);
cell = cells.get(“F24”);
cell.setValue(1600);
cell = cells.get(“F25”);
cell.setValue(1000);
cell = cells.get(“F26”);
cell.setValue(1200);
cell = cells.get(“F27”);
cell.setValue(1300);
cell = cells.get(“F28”);
cell.setValue(1500);
cell = cells.get(“F29”);
cell.setValue(1400);
cell = cells.get(“F30”);
cell.setValue(1000);
//Adding a new sheet
int sindex = workbook.getWorksheets().add();
Worksheet sheet2 = workbook.getWorksheets().get(sindex);
//Naming the sheet
sheet2.setName(“PivotTable”);
//Getting the pivottables collection in the sheet
PivotTableCollection pivotTables = sheet2.getPivotTables();
//Adding a PivotTable to the worksheet
int index = pivotTables.add("=Data!A1:F30", “B3”, “PivotTable1”);
//Accessing the instance of the newly added PivotTable
PivotTable pivotTable = pivotTables.get(index);
//Showing the grand totals
pivotTable.setRowGrand(true);
pivotTable.setColumnGrand(true);
//Setting the PivotTable report is automatically formatted
pivotTable.setAutoFormat(true);
//Setting the PivotTable autoformat type.
pivotTable.setAutoFormatType(PivotTableAutoFormatType.CLASSIC);
//Draging the first field to the row area.
pivotTable.addFieldToArea(PivotFieldType.ROW, 0);
//Draging the third field to the row area.
pivotTable.addFieldToArea(PivotFieldType.ROW, 2);
//Draging the second field to the row area.
pivotTable.addFieldToArea(PivotFieldType.ROW, 1);
//Draging the fourth field to the column area.
pivotTable.addFieldToArea(PivotFieldType.COLUMN, 3);
//Draging the fifth field to the data area.
pivotTable.addFieldToArea(PivotFieldType.DATA, 5);
//Add calculated field to the pivot table
pivotTable.addCalculatedField(“TestField”, “=‘Sale’*2”, true);
//format e.g pivotTable.addCalculatedField(“TestField”, “=Field1’ - ‘Field2’”, true);
//Setting the number format of the first data field
pivotTable.getDataFields().get(0).setNumber(7);
//Saving the Excel file
workbook.save(“f:/files/outpivotTable_test1.xlsx”);
Hope, this helps a bit.
Thank you.