import java.io.File;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.stage.FileChooser;

public class Main extends Application {
@Override
public void start(Stage primaryStage) {
try {
BorderPane root = new BorderPane();
Scene scene = new Scene(root,400,400);
//scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();

String directoryPath = new String("/tmp");
String fileName = new String("test");

FileChooser fileChooser = new FileChooser();
fileChooser.setTitle("Open File");
FileChooser.ExtensionFilter extFilter =
new FileChooser.ExtensionFilter("Text files (*.txt)", "*.txt");
fileChooser.getExtensionFilters().add(extFilter);

fileChooser.setInitialDirectory(new File(directoryPath));
fileChooser.setInitialFileName(fileName);

File file = fileChooser.showOpenDialog(primaryStage);

} catch(Exception e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
launch(args);
}
}