How JavaFX starts exactly

Below is an example of your main application class. I named it "HelloApp" because I needed a name. I also changed launch

to Application.launch

, this is the same but less confusing (see explanations below).

Please note, however (thanks to @Cypher in the comments for this) that the good old method is not needed to run a JavaFX application . If you omit the method from the bottom, compile it and run it with , it will work and might be a little less confusing :) You can still handle command line arguments without , since they are passed to an options object, which you can get from yours with . java

public static void main(String[] args)


main

java HelloApp


main

Application

getParameters()

<sub>My IDE also allows you to run Application

without main

and apparently most of them.</sub>

Speaking of which, let's see what's going on here in your case:

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class HelloApp extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        Parent root = new FXMLLoader(this.getClass().getResource("view.fxml")).load();
        primaryStage.setTitle("Dice Roller");
        primaryStage.setScene(new Scene(root));
        primaryStage.show();
    }

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

}

      

        
        
        
      

    

• HelloApp.main()
  
  causes launch()
  
  
• launch
  
  is a static method in the class Application
  
  that you extend, so you can use directly launch()
  
  , but it is recommended to use the class name when calling static methods, so I replaced the above with Application.launch
  
  . Some IDEs and linters warn you that "a java static method must be statically accessible" if you don't.
• Within the method launch
  
  , the JavaFX runtime (below "JavaFX") determines which class is the caller (using Thread.currentThread().getStackTrace()
  
  , but this is just an interesting implementation detail). The caller class is expected to bejavafx.application.Application
  
  
  <sub>- when working without the main
  
  above doesn't matter, and JavaFX starts here. -sub></sub>
• JavaFX creates an application thread to run the application's launch method, handle input events, and execute animation timing.
• JavaFX creates an instance of the specified Application class
• JavaFX calls init()
  
  (which you can override)
• JavaFX calls start()
  
  (which you must implement yourself) from "JavaFX Application Thread"

The rest of the lifecycle is described in the Application javadoc - the subsequent steps wait for the application to complete (either the application calls Platform.exit()

, or the last window was closed and implicitExit

is true), then JavaFX calls stop()

(which you can override).