[FIXED] JavaFX cannot load my FXML, returning null pointer exception

Issue

I am not sure what the error is I am converting a home project from Swing GUI to JavaFX, using scenebuilder and having a hard time. Please help? Details on my error and project structure below:

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at [email protected]/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:465)
    at [email protected]/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:364)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at [email protected]/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:901)
    at [email protected]/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
    at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.IllegalStateException: Location is not set.
    at [email protected]/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2541)
    at [email protected]/javafx.fxml.FXMLLoader.load(FXMLLoader.java:2516)
    at testify.Runtime.App.start(App.java:22)
    at [email protected]/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:847)
    at [email protected]/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
    at [email protected]/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
    at [email protected]/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
    at [email protected]/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at [email protected]/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at [email protected]/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    ... 1 more
Exception running application testify.Runtime.App

Process finished with exit code 1

here is my project tree:

Here is my main code:

package testify.Runtime;

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

import java.io.IOException;

public class App extends Application {

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

 @Override
 public void start(Stage primaryStage) throws IOException {
    FXMLLoader loader= new FXMLLoader(getClass().getResource("main.fxml"));
    Parent root = (Parent) loader.load();
    Scene home = new Scene(root);

     primaryStage.setTitle("Testify");
     primaryStage.setScene(home); 
         primaryStage.show();
    }
}

Ignore this line for some reason I cannot post a "mostly code" question without having a paragraph written about it on stack overflow and I am not sure why.... never had this issue before on here.

Solution

Just prefix / to the name of your fxml file

FXMLLoader(getClass().getResource("/main.fxml"))

When you dont put a forward slash your URL is being formed as testify/Runtime/main.fxml Whereas your resource is inside the resource folder

Answered By - Naresh Sharma
Answer Checked By - Candace Johnson (JavaFixing Volunteer)