What is going on!!!

Question

https://code.sololearn.com/c8yB4HAOk0eM/?ref=app

windowClosing() is just a method of an interface then who calls windowClosing() method and how when i pressd closing button of frame. I am confused please help

Answer 1

https://docs.oracle.com/javase/7/docs/api/java/awt/event/WindowListener.html