Swing and observer pattern

I had a task at university of making an application using observer pattern to pass the subject (basics of programming). I wanted to show more knowledge, that it is included in syllabus and it backfired on me. I made an application in Swing + sql, heavily dependable on ActionListeners, which I thought, are a significant example of observer pattern. Unfortunately, my project was rejected because I did not write my own implementation of Observer pattern.

My question is, is that even possible with Swing to replace default action listener? I cannot even check a state of a button outside of it. I am really confused at the moment, even though I know the principles of a pattern and looking for help from your side.