why FXMLLoader giving error when used to load a FXML file?

Question

I was following a JavaFX tutorial and wrote the following code.

All the required header files are imported.

Main.java

public class Main extends Application {
@Override
public void start(Stage primaryStage){
    try {
        Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));
    
        Scene scene = new Scene(root);
        scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.setTitle("Random Number Generator");
        primaryStage.show();
    }catch(Exception e) {
        e.printStackTrace();
    }
    
}

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

Main.fxml (created using SceneBuilder)

    <?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane minHeight="100.0" minWidth="100.0" prefHeight="300.0" prefWidth="500.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.MainController">
   <children>
      <Button id="button_generateRandomNumber" layoutX="171.0" layoutY="212.0" mnemonicParsing="false" onAction="#generateRandom" text="Generate Random Number" textAlignment="CENTER" textFill="#1e4d0e" />
      <Label fx:id="message" layoutX="112.0" layoutY="143.0" prefHeight="45.0" prefWidth="258.0" textAlignment="CENTER" />
   </children>
</AnchorPane>

StackTrace

    Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1051)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:900)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.IllegalAccessError: class com.sun.javafx.fxml.FXMLLoaderHelper (in unnamed module @0x5d85fddd) cannot access class com.sun.javafx.util.Utils (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.util to unnamed module @0x5d85fddd
    at com.sun.javafx.fxml.FXMLLoaderHelper.<clinit>(FXMLLoaderHelper.java:38)
    at javafx.fxml.FXMLLoader.<clinit>(FXMLLoader.java:2056)
    at application.Main.start(Main.java:20)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    ... 1 more
Exception running application application.Main

I have tried every combination with getResource("Main.fxml") including relative and absolute path in every way possible still I am getting the error. code is 100% same as of that tutorial.

Answer 1

In order to javafx work, you need to either download and import javafx sdk to your project or specify dependency, if you are using build tool like Maven or Gradle.

Moreover you need to add required modules (in this case javafx's .jars) either by using module-info.java and specifying required modules there, or adding modules to VM arguments - https://openjfx.io/openjfx-docs/#install-javafx.

Bonus: Note that javafx was present in JDK up to version 10. Since version 11, they removed it. That is why you need to import javafx somehow to your project.