Do you have nice examples of refactoring code?

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I am looking for code samples that are good examples of how to refactor code. I would be the happiest if you could provide the code both before and after the refactorings. I am interested in any language, but Java and Python is preferred.

Why? I am planning to make a meetup on the topic and I would need a good base for it.

(I know that there are a lot of stuff out there like refactoring.guru, etc, but I am interested in real-life code samples! :) Also, I have a big bunch of code from our codebase, but I hope you might have even more interesting samples! )

Any help is appreciated! :)

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I just wrote a post on refactoring some Go code to use interfaces. I outline the steps used to refactor this particular pattern: dev.to/chuck_ha/interfaces-in-go-3onc

I would also suggest reading sandimetz.com/99bottles/. It's a fantastic book that refactors code throughout the book and explains how to get there.


This kata is a famous one :


Also, you can take a look at this one :


Java one is also explained in two blog articles here :



Someone at work asked me to refactor their 99 bottles code. I recorded the refactoring so they could see the process and how I think about it. Before is here and after is here. It's a pretty good demonstration of how I refactor.


is it about safe refactoring (with ide)
or refactoring to design patterns? if its the latter, I recommend going through Clean Code by Rob Martin and
Refactoring: Improving the Design of Existing Code by Kent Beck and Martin Fowler


(C#) I just made one that I found in StackOverflow. I implemented the code in a WebApi and it is working fine :D


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Full stack developer from Hungary. #java #javascript #springboot #vuejs #css