Missing JavaFX application class

问题

I have java code like this:

package mypackage;

import javafx.application.Application;
import javafx.stage.Stage;

public class MyApp extends Application{
    public static void main(String args[]){
        launch(args);
    }
    public void start(Stage primaryStage){
        primaryStage.show();
    }
}

and I've compiled it at ~/myjava/src/mypackage/MyApp.class . then, when I'm running from

~$ java -cp myjava/src mypackage/MyApp

why getting error like:

Missing JavaFX application class mypackage/MyApp

I'm using JDK 8.

回答1:

That is because you are calling your application with a directory path instead of the fully qualified classname. The fully qualified classname is composed from the package name and the class name. In your case this is mypackage.MyApp.

Assuming that your compiled class resides in the same folder as the source .java file, call it this way:

java -cp myjava/src mypackage.MyApp

回答2:

After installing Java 15 and JavaFX 13 and some other changes I too was getting "Missing JavaFX application class mypackage/MyApp" and in my case the package name and application were correct. I was using some JDK15 preview functions and I needed the JVM option --enable-preview. In desperation I started to change things, as this used to work. When I removed the --enable-preview option I received error messages relating to the fact I was using preview functions and did not specify it. This told me the loader was in fact finding my application. The error message "Missing JavaFX application class mypackage/MyApp" was incorrect in this case. The problem was I needed to include some user utility classes that MyApp was dependent upon. Once I included the dependent classes in the classpath all was well.

来源：https://stackoverflow.com/questions/39308480/missing-javafx-application-class