final FileChooser fileChooser = new FileChooser();
fileChooser.getExtensionFilters().addAll(
new FileChooser.ExtensionFilter("MSExcel", "*.xls","*.xlsx"),
new FileChooser.ExtensionFilter("Pliki", "*.*")
);
File file = fileChooser.showOpenDialog(ownerStage);
if (file == null) {
return;
}