IntelliJ: Show .java extension as packages

I'm new to IntelliJ and I can't seem to find an option to display the entire file extension in the package view (.java in my case).

As you can see in the sceenshot it simply says "Main" or "Controller" in the left view of the package explorer.

Is there any option to make it display Main.Java and Controller.java (like in the editor on the right)?

Thank you so much!