В текущей версии apache poi 4.1.0
Workbook.setSheetOrder предоставляет то, что вы хотите.
Полный пример:
import org.apache.poi.ss.usermodel.*;
import java.io.FileInputStream;
import java.io.FileOutputStream;
public class ExcelInsertSheet {
public static void main(String[] args) throws Exception {
String fileName = "Excel.xlsx";
String filePath = "./";
Workbook workbook = WorkbookFactory.create(new FileInputStream(filePath + fileName));
Sheet sheet = workbook.createSheet("New Sheet");
workbook.setSheetOrder("New Sheet", 0);
workbook.setSelectedTab(0);
workbook.setActiveSheet(0);
FileOutputStream out = new FileOutputStream(filePath + "Changed" + fileName);
workbook.write(out);
out.close();
workbook.close();
}
}