Jar file: main class not found - IntelliJ IDEA

Question

I developed a Java project in IntelliJ IDEA. When I create the jar artifact as described HERE , everything goes as intended. But when I double-click the generated jar file in the output folder, I get the message:

Could not find main class: DoxCalculator.DoxCalculator. the program will exit.

(My project and main class are called DoxCalculator ). When I open the jar file with WINRAR , I notice that there are only my library files there, but not the compilation output. It’s strange, because in accordance with the project structure window in the artifacts element, it should be enabled.

My MANIFEST.MF looks like this:

 Manifest-Version: 1.0 Main-Class: DoxCalculator.DoxCalculator 

I searched a lot of questions on the forum, but it seems like no such problems have been asked.