Run a Maven Project using IntelliJ IDEA

Refresh the Maven project in the Maven Projects tool window (Reimport All Maven Projects), if it doesn't help, refer to this answer for diagnostics.

The issue is that your source roots were not configured correctly from the Maven model for some reason and the .java file appears in a plain directory instead of the Source root.

You can tell that by the color of the folders and by the icon of the file.

You need to create a Java Project.

File->New->Project->Java->Next->Next->Finish

Then go to the top and do:

Right click parent folder of project->Add Framework Support->Click Maven->Ok

Now Maven should be added to your project and also you should be able to run it

If this doesn't allow you to run the project, click the little drop down box to the left of the grayed out run button and click Edit Configurations.

Then click the + and click Application and set your Main class to the class that has the main method in it, and then it should allow you to run the application.

Hope that helps!