how to use Optional if any API interface returns null indicating missing value

FileChooserDemo.java

import java.io.File;
import java.util.Optional;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.FlowPane;
import javafx.stage.FileChooser;
import javafx.stage.Stage;

/**
 * @author Marcus Bleil, http://www.marcusbleil.de
 */
public class FileChooserDemo extends Application {

	private FileChooser fileChooser;

	@Override
	public void start(Stage primaryStage) {
		fileChooser = new FileChooser();
		FlowPane root = new FlowPane();

		Button fileOpenButton = new Button("file open...");
		fileOpenButton.setOnAction(this::fileChooserButtonEvent);
		root.getChildren().add(fileOpenButton);

		Scene scene = new Scene(root, 400, 300);

		primaryStage.setScene(scene);
		primaryStage.setTitle("FileChooser with Optional Demo");
		primaryStage.show();
	}

	private void fileChooserButtonEvent(ActionEvent event) {
		Optional<File> selectedFile = Optional.ofNullable(fileChooser.showOpenDialog(null));
		if (selectedFile.isPresent()) {
			System.out.println("selected: " + selectedFile.get().getAbsolutePath());
		}
		else {
			System.out.println("file seletion canceled by user");
		}
	}

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