Compiling and running with javFX

Question

I'm not able to run this code. I got this from oracle tutorials. It's a simple hello world application.earlier I wasn't able to compile it but now after including the path for jfxrt.jar file in classpath I'm able to compile but now not able to run.

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

class A extends Application {

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

    public void start(Stage primaryStage) {
        primaryStage.setTitle("Hello World!");
        Button btn = new Button();
        btn.setText("Say 'Hello World'");
        btn.setOnAction(new EventHandler < ActionEvent > () {


            public void handle(ActionEvent event) {
                System.out.println("Hello World!");
            }
        });

        StackPane root = new StackPane();
        root.getChildren().add(btn);
        primaryStage.setScene(new Scene(root, 300, 250));
        primaryStage.show();
    }
}

I'm getting these following errors :

Exception in Application constructor
Exception in thread "main" java.lang.RuntimeException: Unable to construct Appli
cation instance: class A
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherIm
pl.java:393)
        at com.sun.javafx.application.LauncherImpl.access$000(LauncherImpl.java:
47)
        at com.sun.javafx.application.LauncherImpl$1.run(LauncherImpl.java:115)
        at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.NoSuchMethodException: A.<init>()
        at java.lang.Class.getConstructor0(Class.java:2810)
        at java.lang.Class.getConstructor(Class.java:1718)
        at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherIm
pl.java:275)
        ... 3 more

Help me out,how to resolve this. Thanks

Stefan Freitag · Accepted Answer · 2014-03-02 08:38:04Z

1

Make your class public

public class A extends Application

then it should work.

Anyway, do you need another import-Statement? I think the import for ActionEvent is missing:

import javafx.event.ActionEvent;

answered Mar 2, 2014 at 8:38

Stefan Freitag

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4 Comments

user3367768 Over a year ago

hey!! thanks a lot .it worked .now can you explain me the meaning of launch(args),what exactly is it doind?

user3367768 Over a year ago

also primaryStage.setScene(new Scene(root, 300, 250)); primaryStage.show(); actually i'm new to this javafx package,so not aware of these methods and classes.although i know evrythng about javax.swing as i'v used it extensively.Thanks

elToro Over a year ago

if your are not familiar with JavaFX and want to use it, I would recommend to start with some basic tutorials. They will give you a good overview. e.g. start here: oracle.com/technetwork/java/javafx/documentation/index.html

user3367768 Over a year ago

hey! i'v already gone through some of these tutorials but they're all about how to create a frame,graphs,animations etc.none of them explains how exactly it's working.like how the control flows in the program.how does the start() gets invoked?how is launch(args) working.

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