after I have installed openjdk-11.jdk and openjfx I was able to get openjfx ip and running within Eclipse following this thread: How to add JavaFX runtime to Eclipse in Java 11?
But all my attempts to let it run in the command line failed (I have added the path to the openfx as well: /usr/share/openjfx/lib).
Within the bin folder /test-fx/bin I call
java application.Main and I receive java.lang.NoClassDefFoundError: javafx/application/Application
Conclusion: Java does find Main.main(), but cannot find the JavaFX Application class.
test-fx is just my Eclipse folder.
the structure is like this:
test-fx
    src
        application
            Main.java
    bin
        application
            Main.class
And this is Main.java:
public class Main extends Application {
    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void start() {
        ...
    }
}
Does anybody know a good solution on that? What is recommended? How should I define PATH, where should it point to?