Run button of the IDEA

You're right, by default IDEA runs the last configuration and not the file you have currently open/active in your editor. This can be annoying for beginners like us who have only a few files and basically all of them are runnable classes with a main method. But consider the other way around: You are working on a larger program, currently editing some data or config-file. Then you hit "run" and IDEA would - instead of running your main-method, try to execute the data file you are working on. There are, however, a few convenient ways to run the currently open file: 1. Right click anywhere in your currently open file that you want to run and select the run-option from the context menu 2. The keyboard shortcut for running the last configuration (same thing as the run-button does) is SHIFT+F10, the shortcut for running the currently active file is CTRL+SHIFT+F10. (This may be different on your machine, depending on the operating system etc., but you can manually configure the keyboard shortcuts) Happy coding anyway!