Facing error in javafx project

Basically I am making a library assistant desktop app using JavaFX and scene builder. I am facing this error.


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: javafx.fxml.LoadException: Error resolving onAction='#addbook', either the event handler is not in the Namespace or there is an error in the script.
file:/C:/Users/MUHAMMAD%20ZAHOOR/Documents/NetBeansProjects/LibraryAssitant/dist/run1601638133/LibraryAssitant.jar!/libraryassitant/ui/addbook/FXMLDocument.fxml:36

	at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2597)
	at javafx.fxml.FXMLLoader.access$100(FXMLLoader.java:103)
	at javafx.fxml.FXMLLoader$Element.processEventHandlerAttributes(FXMLLoader.java:610)
	at javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:770)
	at javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2823)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2532)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
	at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
	at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
	at libraryassitant.ui.addbook.LibraryAssitant.start(LibraryAssitant.java:22)
	at com.sun.javafx.application.LauncherImpl.lambda$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 libraryassitant.ui.addbook.LibraryAssitant
Java Result: 1

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
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thanks, i will follow it next time