How to close the window when you click?

@FXML Button btnOK; // Для этой кнопки нужно сделать слушателя который будет закрывать это окно private StorageVariables storageVariables=new StorageVariables(); private Stage stageMenu; private String language; private FXMLLoader fXMLLoader; public void showMessageDialog()throws IOException{ StorageVariables storageVariables = new StorageVariables(); language=storageVariables.getLanguage(); fXMLLoader = new FXMLLoader(); fXMLLoader.setLocation(getClass().getResource("MessageDialog.fxml")); Parent panel = null; try { panel = FXMLLoader.load(getClass().getResource("MessageDialog.fxml")); } catch (IOException e) {} Scene scene=new Scene(panel,410,150); stageMenu=new Stage(); stageMenu.setScene(scene); stageMenu.initModality(Modality.APPLICATION_MODAL); stageMenu.showAndWait(); } 

// This method - the controller of the 'btnOK' button handles button presses

  public void inquiryQuestionBtnOK() { System.out.println(" *Кнопка 'btnOK' нажата"); System.out.println(""); stageMenu.close(); } 

When you click on the button, an error flies:

 java.lang.RuntimeException: java.lang.reflect.InvocationTargetException at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1456) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28) at javafx.event.Event.fireEvent(Event.java:171) at javafx.scene.Scene$MouseHandler.process(Scene.java:3369) at javafx.scene.Scene$MouseHandler.process(Scene.java:3209) at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3164) at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1582) at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2267) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173) at java.security.AccessController.doPrivileged(Native Method) at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292) at com.sun.glass.ui.View.handleMouseEvent(View.java:530) at com.sun.glass.ui.View.notifyMouse(View.java:924) at com.sun.glass.ui.win.WinApplication._enterNestedEventLoopImpl(Native Method) at com.sun.glass.ui.win.WinApplication._enterNestedEventLoop(WinApplication.java:96) at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:384) at com.sun.glass.ui.EventLoop.enter(EventLoop.java:83) at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:523) at javafx.stage.Stage.showAndWait(Stage.java:438) at sample.MyTool.showMessageDialog(MyTool.java:66) at sample.ControllerCreateNewBuildMods.inquiryQuestionBtnReady(ControllerCreateNewBuildMods.java:168) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:75) at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:279) at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1453) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28) at javafx.event.Event.fireEvent(Event.java:171) at javafx.scene.Scene$MouseHandler.process(Scene.java:3369) at javafx.scene.Scene$MouseHandler.process(Scene.java:3209) at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3164) at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1582) at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2267) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173) at java.security.AccessController.doPrivileged(Native Method) at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292) at com.sun.glass.ui.View.handleMouseEvent(View.java:530) at com.sun.glass.ui.View.notifyMouse(View.java:924) at com.sun.glass.ui.win.WinApplication._enterNestedEventLoopImpl(Native Method) at com.sun.glass.ui.win.WinApplication._enterNestedEventLoop(WinApplication.java:96) at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:384) at com.sun.glass.ui.EventLoop.enter(EventLoop.java:83) at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:523) at javafx.stage.Stage.showAndWait(Stage.java:438) at sample.CreateNewBuildMods.showMenu(CreateNewBuildMods.java:37) at sample.ControllerMainMenu.inquiryQuestionBtnMainMenuFirstBuild(ControllerMainMenu.java:286) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:75) at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:279) at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1453) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33) at javafx.event.Event.fireEvent(Event.java:171) at javafx.scene.Scene$MouseHandler.process(Scene.java:3369) at javafx.scene.Scene$MouseHandler.process(Scene.java:3209) at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3164) at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1582) at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2267) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173) at java.security.AccessController.doPrivileged(Native Method) at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292) at com.sun.glass.ui.View.handleMouseEvent(View.java:530) at com.sun.glass.ui.View.notifyMouse(View.java:924) at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:17) at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:67) at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:75) at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:279) at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1453) ... 106 more Caused by: java.lang.NullPointerException at sample.MyTool.inquiryQuestionBtnOK(MyTool.java:80) ... 116 more 

I can't figure out how to do this. help me please