问我面对的是java.lang.reflect.InvocationOnTargetException

EN

package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

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

@Override
public void start(Stage primaryStage) throws Exception {


    Parent root = FXMLLoader.load(getClass().getResource("testcode.fxml"));
    Scene scene = new Scene(root);
    primaryStage.setScene(scene);
    primaryStage.show();
}
}

    <?xml version="1.0" encoding="UTF-8"?>
    <?import javafx.scene.control.Button?>
    <?import javafx.scene.layout.AnchorPane?>

<AnchorPane prefHeight="420.0" prefWidth="508.0" xmlns="http://javafx.com/javafx/10.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="MainController.java">
   <children>
      <Button id="btn1" layoutX="216.0" layoutY="178.0" mnemonicParsing="false" onAction="#generateRandom" text="Test Button" />
   </children>
</AnchorPane>

    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(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.base/java.lang.reflect.Method.invoke(Unknown Source)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(Unknown Source)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(Unknown Source)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.base/java.lang.reflect.Method.invoke(Unknown Source)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(Unknown Source)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(Unknown Source)
    at java.base/java.lang.Thread.run(Unknown Source)
Caused by: javafx.fxml.LoadException: 
/E:/eclipse/eclipse-workspace/JavaFXDemo/bin/application/testcode.fxml:6

    at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.access$700(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processAttribute(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader$Element.processStartElement(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processStartElement(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.processStartElement(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(Unknown Source)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(Unknown Source)
    at application.Main.start(Main.java:19)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(Unknown Source)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11(Unknown Source)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(Unknown Source)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(Unknown Source)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(Unknown Source)
    ... 1 more
Caused by: java.lang.ClassNotFoundException: MainController.java
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown Source)
    at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
    ... 23 more
Exception running application application.Main

package Controller;
import java.util.Random;
import javafx.event.ActionEvent;

public class MainController {

public void generateRandom(ActionEvent event) {

    Random random = new Random();
    int rand = random.nextInt(100) + 1;
    System.out.println(Integer.toString(rand));
}

 }