JDK update - with existing project

I have updated my JDK from 1.7 to 1.8, because in JavaFX the DatePicker did not work at all. (It told me to upgrade to FX8 in order to use this component)

My project was created a month ago in 1.7 and when I change the path to the new 1.8, or add manually (by link the library where it can be found) my code does not run, the error message links to the previous version of the JDK.

Is there any possible way to change the JDK while I keep my project? I really would like to use the datepicker in my application to make the user able to choose a date and a time.

OR/AND

Could you refer a good component similar to datepicker which can be used in JavaFX environment?

Thank you!!

   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:497)
at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
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:497)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:323)
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:497)
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$152(LauncherImpl.java:182)
at com.sun.javafx.application.LauncherImpl$$Lambda$50/1688376486.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)

  Caused by: javafx.fxml.LoadException: 
      file:/C:/Users/MrFireman/Documents/NetBeansProjects/Utiokos_program18/dist/run1504948759/Utiokos_program18.jar!/utiokos_program18/Foablak.fxml

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2605)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2583)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3218)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3179)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3152)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3128)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3108)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3101)
at utiokos_program18.Utiokos_program.start(Utiokos_program.java:30)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
at com.sun.javafx.application.LauncherImpl$$Lambda$53/1117189665.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/683287027.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
at com.sun.javafx.application.PlatformImpl$$Lambda$48/327433472.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
at com.sun.javafx.application.PlatformImpl$$Lambda$46/254413710.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
at com.sun.glass.ui.win.WinApplication$$Lambda$36/326549596.run(Unknown Source)
... 1 more
   Caused by: java.lang.NullPointerException
at utiokos_program18.FoablakController.initialize(FoablakController.java:391)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2552)
... 22 more
 Exception running application utiokos_program18.Utiokos_program
 Java Result: 1