加载fxml时出现“ javafx.fxml.LoadException”错误

Question

对于一个项目，我需要使用JavaFX创建一个GUI。因此，在我密切关注的Scene Builder / JavaFX教程中，我创建了一个非常基本的GUI。但是加载似乎无法正常工作，并引发LoadException。我在网上似乎遇到了一些类似的问题，但是他们的答案似乎都无法解决我的问题。我已经尽力尝试类似的指南和教程，做了很多googleFoo，但是它不会加载。

这是主要的：

package stacksim;

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

public class stacksim extends Application {

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

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

       try {
            // Read file fxml and draw interface.
            Parent root = FXMLLoader.load(getClass()
                    .getResource("stacksim.fxml"));

            primaryStage.setTitle("Stack Simulation");
            primaryStage.setScene(new Scene(root));
            primaryStage.show();

        } catch(Exception e) {
            e.printStackTrace();
        }
    }

}

控制器：

package stacksim;

import java.net.URL;
import java.util.ResourceBundle;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.geometry.Pos;

import javafx.scene.control.Button;
import javafx.scene.control.Label;

import javafx.scene.layout.GridPane;

import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.transform.Translate;

/**
 * FXML Controller class
 *
 * @author Dell
 */
public class stacksimcontroller implements Initializable {
    @FXML
    private Button btnPush;
    @FXML
    private Button btnPop;
    @FXML
    private Button btnExit;
    @FXML
    private GridPane gridBoxBall;
    @FXML
    private GridPane gridBoxNum;
    @FXML
    private Label description;    
    private int curColumn = 0; 
    private int count = 0;

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }
    public void actionPush(ActionEvent event) {       
        System.out.println("Button Push Clicked!");
        if (curColumn >= 10) {
            description.setText("Stack is fully, you can't push more !");        
        } else {
            addCircle(curColumn, 0);
            addLabel(curColumn, 0);
            System.out.println(' ');
            count++;
            description.setText("Push successfully!");
            curColumn++;
            System.out.println(curColumn);
        }
    }

    public void actionPop(ActionEvent event) {        
        System.out.println("Button Pop Clicked!");
        if (curColumn == 0) {
            description.setText("Stack Empty! Nothing to pop!");
            System.out.println(curColumn);
        } else if (curColumn == 1) {
            curColumn--;
            gridBoxBall.getChildren().remove(curColumn); 
            gridBoxNum.getChildren().remove(curColumn);

            description.setText("Pop successfully!");
            System.out.println(curColumn);

        } else {
            curColumn--;
            gridBoxBall.getChildren().remove(curColumn);
            gridBoxNum.getChildren().remove(curColumn);

            System.out.println(curColumn);

            for (int i = 0; i < curColumn; i++) {
                Translate translate = new Translate();
                translate.setZ(0);
                translate.setY(0);
                translate.setX(0);
                gridBoxBall.getChildren().get(i).getTransforms().addAll(translate);
                gridBoxNum.getChildren().get(i).getTransforms().addAll(translate);

            }
             description.setText("Pop successfully!");
        }

    }



    public void actionExit(ActionEvent event) {
        System.exit(0);
    }

    public void addCircle(int col, int row){
        Circle circle = new Circle(20);
        circle.setFill(Color.FIREBRICK);            
        gridBoxBall.add(circle, col, row);


    }
    public void addLabel(int col, int row){
        Label label = new Label(count + "");     
        label.setPrefSize(40, 40);
        label.setAlignment(Pos.CENTER);
        gridBoxNum.add(label, col, row);
    }
}

fxml：

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

<?import javafx.scene.text.*?>
<?import javafx.scene.shape.*?>
<?import javafx.geometry.*?>
<?import java.lang.*?>
<?import java.net.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="queuedemon.QueueDemonController">
   <children>
      <Label alignment="CENTER" contentDisplay="CENTER" layoutX="-4.0" layoutY="-3.0" prefHeight="65.0" prefWidth="606.0" text="STACK HAVING 10 SLOTS" textFill="FIREBRICK">
         <font>
            <Font name="Arial Bold" size="26.0" />
         </font>
      </Label>
      <HBox alignment="CENTER" layoutX="1.0" layoutY="335.0" prefHeight="51.0" prefWidth="600.0" spacing="100.0">
         <children>
            <Button fx:id="btnPush" alignment="CENTER" mnemonicParsing="false" onAction="#actionPush" text="PUSH" textFill="FIREBRICK" />
            <Button fx:id="btnPop" alignment="CENTER" mnemonicParsing="false" onAction="#actionPop" text="POP" textFill="FIREBRICK" />
         </children>
         <opaqueInsets>
            <Insets />
         </opaqueInsets>
         <padding>
            <Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
         </padding>
      </HBox>
      <Label fx:id="description" alignment="CENTER" layoutX="2.0" layoutY="281.0" prefHeight="17.0" prefWidth="600.0" textFill="FIREBRICK">
         <font>
            <Font size="14.0" />
         </font>
      </Label>
      <GridPane fx:id="gridBoxBall" hgap="10.0" layoutX="62.0" layoutY="180.0" prefHeight="40.0" prefWidth="500.0" AnchorPane.bottomAnchor="180.0" AnchorPane.leftAnchor="62.0" AnchorPane.rightAnchor="38.0" AnchorPane.topAnchor="180.0">
        <columnConstraints>
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
        </columnConstraints>
        <rowConstraints>
          <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
        </rowConstraints>
         <padding>
            <Insets left="10.0" right="10.0" />
         </padding>
      </GridPane>
      <GridPane fx:id="gridBoxNum" hgap="10.0" layoutX="62.0" layoutY="241.0" prefHeight="40.0" prefWidth="500.0">
         <columnConstraints>
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
         </columnConstraints>
         <rowConstraints>
            <RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
         </rowConstraints>
         <padding>
            <Insets left="10.0" right="10.0" />
         </padding>
      </GridPane>
      <Button fx:id="btnExit" alignment="CENTER" layoutX="537.0" layoutY="14.0" mnemonicParsing="false" onAction="#actionExit" text="EXIT" textFill="FIREBRICK" />
   </children>
</AnchorPane>

错误：

javafx.fxml.LoadException: 
/E:/Study/OOP/Java/JavaMidterm/TestQueueMidterm/bin/stacksim/stacksim.fxml

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2848)
    at javafx.fxml.FXMLLoader.processImport(FXMLLoader.java:2692)
    at javafx.fxml.FXMLLoader.processProcessingInstruction(FXMLLoader.java:2661)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2517)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
    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 stacksim.stacksim.start(stacksim.java:31)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException
    at javafx.fxml.FXMLLoader.loadType(FXMLLoader.java:2899)
    at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2846)
    ... 20 more