It's been a few years since I've been heavily into Java. Coming back to it I'm seeing this pattern all over the place: ratingBar.setOnRatingBarChangeListener(new OnRatingBarChangeListener() { public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) { // do work } }); This looks more like Functional programming to me. It's a nice pattern but how is it possible to pass a method like this? In the old days a class was a class, and once compiled there was little you could do to it. My questions are: Can anyone let me know what this pattern is called? How can I write a class that can be instantiated in this way. Are there any other useful examples of functional patterns that have made their way into Java? What do I need to Google to read more about this? Thanks.