"Run File" is often disabled after introducing a main() method

Often when introducing a new `main` method into an existing class, the "Run File" and "Debug File" menu entries are still disabled and is therefore impossible to execute this `main` method.

In most cases it is necessary to closes netbeans and clear the netbeans cache to be able to execute it, which is absolutely counterproductive if such a method is only temporarily inserted for testing purposes.

It may be that this only happens with Maven projects, since all my projects are maven based.

Please see the attached screenshot that shows the context menu after introducing a new `main` method.