where to place suggested code

Question

I am a newbie to Spring. I have a spring project that I want to run some code after it finishes startup. There is a sol'n offered here:

suggested solution

specifically, I would like to try:

 @EventListener(ApplicationReadyEvent.class) public void doSomethingAfterStartup() { System.out.println("hello world, I have just started up"); }

My question is where in the project to put this code? (there are a bunch of code files in various directories)