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JavaFX Entry Point

Entry point

The entry point for Java programs we have written so far this year is the main() method. 

public class Driver {
    public static void main(String[] args) {
        // Entry point
    }
}

In a JavaFX program, the entry point is the start() method of a class that extends javafx.application.Application. Here is the Application API for reference

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

public class MyApp extends Application {

    @Override
    public void start(Stage stage) throws Exception {
        // Entry point
    }
}

Note in the API that Application is abstract because it contains an abstract method named start(). This is the entry point for a JavaFX application and your class must override this abstract method.

Running a JavaFX program

Finally, to run a JavaFX program you need to call a JavaFX method named launch() in your program's main() method.

launch() is a special method of the Application class that sets up a JavaFX application and calls start() for you. Never call start() directly. Read the top section of the Application API if you want to know why. 

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

public class MyApp extends Application {
    // You still need a main method, but it calls launch to start JavaFX
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        // Entry point
        stage.setTitle("My Window (aka Stage)");
        stage.setWidth(500);
        stage.setHeight(500);
        stage.show();
    }

}

Last modified: February 27, 2023

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