Java Fx displayed Exception in Application start method

Question

I am a beginner of JavaFX. When I create a JavaFX project with Scene Builder. I just run and check the default user interface and got an error. The full stack trace is attached below. I don't know how to solve this problem.

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$1(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at javafxapplication9.JavaFXApplication9.start(JavaFXApplication9.java:22)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$7(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$5(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$6(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$4(WinApplication.java:186)
    ... 1 more
Exception running application javafxapplication9.JavaFXApplication9
C:\Users\kobinath\Documents\NetBeansProjects\JavaFXApplication9\nbproject\build-impl.xml:1052: The following error occurred while executing this line:
C:\Users\kobinath\Documents\NetBeansProjects\JavaFXApplication9\nbproject\build-impl.xml:806: Java returned: 1
BUILD FAILED (total time: 1 second)

i don't know why. what i tried so far i attached below

public class JavaFXApplication9 extends Application {
    
    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));
        
        Scene scene = new Scene(root);
        
        stage.setScene(scene);
        stage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

FXMLDocumentController

public class FXMLDocumentController implements Initializable {
    
    @FXML
    private Label label;
    
    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("You clicked me!");
        label.setText("Hello World!");
    }
    
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    
    
}

I don't use [NetBeans](https://netbeans.apache.org/). I use [Eclipse](https://www.eclipse.org/ide/). Do you know in which folder file `JavaFXApplication9.class` is located? If you do, check if file `FXMLDocument.fxml` is in the same folder. — Abra, Dec 20 '20 at 08:19
i did this 3 months ago it worked so problem. today i get the trouble. — Programmer Hari, Dec 20 '20 at 08:20
Did you try ./FXMLDocument or the full path? I.e. `"/javafxapplication9/FXMLDocument.xml"`? — Benjamin Marwell, Dec 20 '20 at 09:38
see the troubleshooting section of https://stackoverflow.com/questions/61531317/how-do-i-determine-the-correct-path-for-fxml-files-css-files-images-and-other .. — kleopatra, Dec 20 '20 at 11:32
@Ben please don't suggest random experiments (your first suggestion is plain wrong, the second doesn't make a difference, provided the resources are where the OP expects them to be) — kleopatra, Dec 20 '20 at 11:34
@kleopatra that is actually not true. On modularized builds it can make a difference. Depending on what JavaFX will invoke. My best guess is that Netbeans doesn’t copy the file to the target dir, but how can we now with that little information? — Benjamin Marwell, Dec 20 '20 at 18:48

Java Fx displayed Exception in Application start method

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