how to make javafx full screen default

To set a JavaFX application to be full-screen by default, you can use the fullScreenExitHint and setFullScreen methods of the Stage class.

Here is an example of how you can set a JavaFX application to be full-screen by default:

import javafx.application.Application;
import javafx.stage.Stage;

public class FullScreenExample extends Application {

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

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Full-Screen Application");
        primaryStage.setFullScreenExitHint("Press Escape to exit full-screen mode");
        primaryStage.setFullScreen(true);

        // add your application content here
        // ...

        primaryStage.show();
    }
}

In this example, the setFullScreenExitHint method is used to set the message that will be displayed when the user tries to exit full-screen mode. The setFullScreen method is then used to set the application to full-screen mode. The show method is called to display the stage.

You can also use the fullScreenExitKeyCombination and setFullScreenExitKeyCombination methods of the Stage class to set the key combination that will be used to exit full-screen mode.

For example:

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.input.KeyCode;
import javafx.scene.input.KeyEvent;
import javafx.stage.Stage;

public class FullScreenExample extends Application {

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

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Full-Screen Application");
        primaryStage.setFullScreenExitHint("Press Escape to exit full-screen mode");
        primaryStage.setFullScreenExitKeyCombination(KeyCode.ESCAPE);
        primaryStage.setFullScreen(true);

        // add your application content here
        // ...

        primaryStage.show();
    }
}

In this example, the setFullScreenExitKeyCombination method is used to set the ESCAPE key as the key combination that will be used to exit full-screen mode.

Keep in mind that the user can still exit full-screen mode by pressing the appropriate key combination or using the system's full-screen toggle button, if available.