import javafx.application.Application;
import javafx.application.Platform;
import javafx.concurrent.Task;
import javafx.concurrent.Worker;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;

public class TaskExample extends Application {
    @Override
    public void start(final Stage primaryStage) throws Exception {
        String osName = System.getProperty("os.name");
        String javaVersion = System.getProperty("java.version");
        String vmInfo = System.getProperty("java.vm.version") +
                        " (" + System.getProperty("os.arch") + ")";

        System.out.println("OS: " + osName);
        System.out.println("Version: " + javaVersion);
        System.out.println("VM Info: " + vmInfo);
        System.out.println("----------------------------------------");

        Task<Void> task = new Task<Void>() {
            @Override
            protected Void call() throws Exception {
                return null;
            }

            @Override
            protected void running() {
                System.out.println("running()");
            }
        };

        task.stateProperty().addListener((o, old, newState) -> {
            if(newState == Worker.State.RUNNING) {
                System.out.println("observed RUNNING");
            }
        });

        new Thread(task).start();

        Button close = new Button("Close");
        close.setOnAction(event -> Platform.exit());
        primaryStage.setScene(new Scene(close));
        primaryStage.show();
    }

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