FileChooser fileChooser = new FileChooser();
fileChooser.setTitle("Import new data");
fileChooser.getExtensionFilters().add(new FileChooser.ExtensionFilter("CSV Files", "*.csv"));
fileChooser.setInitialDirectory(new File("."));
File file = fileChooser.showOpenDialog(window);
if (file != null) { // do things
} else { // no file got selected
}