where is the error??? showing "java.lang.reflect.InvocationTargetException" - javafx

Question

Why this exception is happening ,I tried to fix it but seeing no solution
but, I find no clue to solve those exceptions
//main
package filebrowser;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.stage.Stage;
public class FileBrowser extends Application
{
#Override
public void start(Stage stage) throws Exception{
Parent root=FXMLLoader.load(getClass().getResource("fileExplorer.fxml"));
Scene scene=new Scene(root);
stage.setTitle("Windows File Explorer");
stage.getIcons().add(new
Image(ClassLoader.getSystemResourceAsStream("filebrowser/application-x-executable.png")));
stage.setScene(scene);
stage.show();
}
public static void main(String[] args){
launch(args);
}
}
/*controller class this is the main control class i think error should be there but could not figure out it yet.
package filebrowser;
import java.io.File;
import java.net.URL;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ListView;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
public class FXMLcontroller{
#FXML
private ListView<String> listviewFiles;
#FXML
private TreeView<String> treeviewFileBrowse;
public void initialize() {
assert treeviewFileBrowse != null : "fx:id=\"treeviewFileBrowse\" was not injected: check your FXML file 'FileExplorer.fxml'.";
TreeItem<String> rootNode=new TreeItem<>("This PC",new ImageView(new Image(ClassLoader.getSystemResourceAsStream("filebrowser/computer.png"))));
Iterable<Path> rootDirectories=FileSystems.getDefault().getRootDirectories();
for(Path name:rootDirectories){
FilePathTreeItem treeNode=new FilePathTreeItem(new File(name.toString()));
rootNode.getChildren().add(treeNode);
}
rootNode.setExpanded(true);
this.treeviewFileBrowse.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
this.treeviewFileBrowse.setRoot(rootNode);
//this.listviewFiles.getSelectionModel().setSelectionMode(SelectionMode.MULTIPLE);
}
}
//file path tree class
package filebrowser;
import java.io.File;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.scene.control.TreeItem;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
public class FilePathTreeItem extends TreeItem<String>{
public static Image folderCollapseImage=new Image(ClassLoader.getSystemResourceAsStream("filebrowser/folder.png"));
public static Image folderExpandImage=new Image(ClassLoader.getSystemResourceAsStream("filebrowser/folder-open.png"));
public static Image fileImage=new Image(ClassLoader.getSystemResourceAsStream("filebrowser/text-x-generic.png"));
private boolean isLeaf;
private boolean isFirstTimeChildren=true;
private boolean isFirstTimeLeaf=true;
private final File file;
public File getFile(){return(this.file);}
private final String absolutePath;
public String getAbsolutePath(){return(this.absolutePath);}
private final boolean isDirectory;
public boolean isDirectory(){return(this.isDirectory);}
public FilePathTreeItem(File file){
super(file.toString());
this.file=file;
this.absolutePath=file.getAbsolutePath();
this.isDirectory=file.isDirectory();
if(this.isDirectory){
this.setGraphic(new ImageView(folderCollapseImage));
//add event handlers
this.addEventHandler(TreeItem.branchCollapsedEvent(),new EventHandler(){
#Override
public void handle(Event e){
FilePathTreeItem source=(FilePathTreeItem)e.getSource();
if(!source.isExpanded()){
ImageView iv=(ImageView)source.getGraphic();
iv.setImage(folderCollapseImage);
}
}
} );
this.addEventHandler(TreeItem.branchExpandedEvent(),new EventHandler(){
#Override
public void handle(Event e){
FilePathTreeItem source=(FilePathTreeItem)e.getSource();
if(source.isExpanded()){
ImageView iv=(ImageView)source.getGraphic();
iv.setImage(folderExpandImage);
}
}
} );
}
else{
this.setGraphic(new ImageView(fileImage));
}
//set the value (which is what is displayed in the tree)
String fullPath=file.getAbsolutePath();
if(!fullPath.endsWith(File.separator)){
String value=file.toString();
int indexOf=value.lastIndexOf(File.separator);
if(indexOf>0){
this.setValue(value.substring(indexOf+1));
}else{
this.setValue(value);
}
}
}
#Override
public ObservableList<TreeItem<String>> getChildren(){
if(isFirstTimeChildren){
isFirstTimeChildren=false;
super.getChildren().setAll(buildChildren(this));
}
return(super.getChildren());
}
#Override
public boolean isLeaf(){
if(isFirstTimeLeaf){
isFirstTimeLeaf=false;
isLeaf=this.file.isFile();
}
return(isLeaf);
}
private ObservableList<FilePathTreeItem> buildChildren(FilePathTreeItem treeItem){
File f=treeItem.getFile();
if((f!=null)&&(f.isDirectory())){
File[] files=f.listFiles();
if (files!=null){
ObservableList<FilePathTreeItem> children=FXCollections.observableArrayList();
for(File childFile:files){
children.add(new FilePathTreeItem(childFile));
}
return(children);
}
}
return FXCollections.emptyObservableList();
}
}
//FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.*?><?import javafx.scene.effect.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<AnchorPane xmlns="http://javafx.com/javafx/8"
xmlns:fx="http://javafx.com/fxml/1"
fx:controller="filebrowser.FXMLcontroller">
<children>
<TreeView fx:id="treeviewFileBrowse" layoutX="2.0" layoutY="78.0"
prefHeight="304.0" prefWidth="171.0" />
<Button layoutX="14.0" layoutY="35.0" mnemonicParsing="false"
prefHeight="22.0" prefWidth="29.0" text="<" />
<MenuBar layoutY="2.0" prefHeight="25.0" prefWidth="600.0">
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Home">
<items>
<MenuItem mnemonicParsing="false" text="Delete" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="Share">
<items>
<MenuItem mnemonicParsing="false" text="About" />
</items>
</Menu>
<Menu mnemonicParsing="false" text="View">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
</menus>
</MenuBar>
<Button layoutX="43.0" layoutY="35.0" mnemonicParsing="false"
prefHeight="22.0" prefWidth="29.0" text=">" />
<TextField layoutX="475.0" layoutY="35.0" prefHeight="25.0"
prefWidth="111.0" promptText="Search quick text" />
<TableView layoutX="179.0" layoutY="78.0" prefHeight="304.0"
prefWidth="417.0">
<columns>
<TableColumn prefWidth="50.0" text="Icon" />
<TableColumn prefWidth="144.0" text="Name" />
<TableColumn minWidth="0.0" prefWidth="106.0" text="Date Modified" />
<TableColumn minWidth="0.0" prefWidth="69.0" text="Size" />
<TableColumn minWidth="0.0" prefWidth="45.0" text="Type" />
</columns>
</TableView>
<TextField layoutX="102.0" layoutY="35.0" prefHeight="25.0"
prefWidth="365.0" promptText="Search Here" />
<AmbientLight color="CHARTREUSE" lightOn="true" />
<PointLight color="CHARTREUSE" lightOn="true" />
</children>
</AnchorPane>`
//output exception
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$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException: Location is required.
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at filebrowser.FileBrowser.start(FileBrowser.java:14)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Exception running application filebrowser.FileBrowser
Java Result: 1