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Refactoring: Improving the Design of Existing Code

(Addison-Wesley Object Technology Series)

4.25  ·  Rating details ·  6,891 ratings  ·  273 reviews
Fully Revised and Updated-Includes New Refactorings and Code Examples "Any fool can write code that a computer can understand. Good programmers write code that humans can understand."
--M. Fowler (1999) For more than twenty years, experienced programmers worldwide have relied on Martin Fowler's Refactoring to improve the design of existing code and to enhance software mai
Hardcover, Second edition, 448 pages
Published November 19th 2018 by Addison-Wesley Professional (first published January 1st 1999)
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Madhur Ahuja The book examples are in Java not C#. You will still benefit from it. Make sure you have read Gang of four design patterns before reading this book.

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Jesse Buss
Overall I was disappointed in this book. Modern tools and IDE's have removed nearly all of the pain points that are laid out in this book, which made reading annoying and tiresome. I skipped the "Mechanics" section of every single refactor because they are just not relevant in 2016. Your compiler and IDE will tell you every thing you need to know in nearly all cases.

That being said the content is good, albeit very basic. I would recommend this to someone who is just out of college or with littl
Ivan Idris
Jan 22, 2012 rated it it was amazing  ·  review of another edition
Refactoring is the process of rewriting software, without changing the way it functions, in order to improve its readability, testability or maintanability. A book has been written on the subject by Martin Fowler. Some of the chapters were written by other people.

“Refactoring: Improving the Design of Existing Code” is focused on OO programming (lots of Java examples) and Agile practices. It is setup as a catalog of refactoring techniques. Each page dedicated to a refactoring is clearly marked, s
David Workman
While this book is more of a reference book than a book to read through a memorise (and I intend to use it as such in the future), this book is well worth having for software engineers looking to improve their practices. Even if you don't subscribe to Martin Fowler's 'lots of small methods and classes' style of programming (and I admit, it takes some getting used to), the techniques in this book are still useful and applicable to any software project.

The book consists mainly of a catalog of ref
Apr 27, 2019 rated it it was amazing  ·  review of another edition
The second edition of the classic Refactoring book by Martin Fowler is more than just an update. It switched from Java to JavaScript for most of the examples, what lead to many renames of refactorings (for example: extract function instead of extract method). Most of the classical refactorings are still there and it had space for new ones like Split Phase – one practice I found by myself and now can refer to using a name. This tradition of giving names to practices around refactoring is continue ...more
Jan 31, 2012 rated it really liked it  ·  review of another edition
If you are interested in improving and maintaining the quality of your code this book should be on your reading list. It is not the kind of book you read once and forget about it. When you are doing refactoring it’s always recommended to come back and check the categories explained in it.

What I really enjoyed is that it confirmed some of the ideas I already had about software development. On the first hand you should have a robust test suite in order to be certain that refactoring didn’t change
Ehsan Gazar
Feb 07, 2019 rated it it was amazing  ·  review of another edition
This book is not just for refactoring, it's for understanding how professional are thinking about their code. You can use these methods even in writing the first line of your code.

This is one of the books that every developer should read to transform his knowledge to be in more readable and flexible code.
Ashkan Entezari
Apr 09, 2020 rated it really liked it  ·  review of another edition
Refactoring is definitely an educational read for any programmer. It covers many areas of refactoring from why we need it to how we should do it and get it done. The only regret that I have right now is reading the first edition of this book (+20 years old!) while there was a second edition which was published 2 years ago. When I read the change-log, it didn't seem like very different but as soon as I picked-up the book I realized how outdated it is in some parts. There are tons of discussions a ...more
Mar 19, 2019 rated it it was amazing  ·  review of another edition
You hear something about refactoring and you want to see what it is ?
You want to make your code better but don't know how to do it ?

If your answer is yes, then this book is for you.
Martin Fowlers 'Refactoring' is in my opinion the best book about this subject.

Author describes many refactoring techniques and explain how and when to use them.
Each technique has it's own example write in javascript - code is very easy to understand
and you won't have any problems to apply it in your language of choic
Steliyan Stoyanov
Dec 04, 2016 rated it it was amazing  ·  review of another edition
Shelves: tech
This book is a must-read for every software developer. I would personally recommend it to my team members.

I totally agree with Martin and his vision that the changes should be incremental. I think everyone that tried a "complete rewrite" at some point failed or at least achieved unsatisfactory results. Maybe they didn't completed in time or didn't achieve the expected results.

The most important aspect that is emphasized in the book is that you should apply refactoring when you need to, not just
Mar 25, 2020 rated it it was amazing  ·  review of another edition
Biggest takeaway is to take really small steps when refactoring, which the book demonstrated a lot with detailed examples. A lot of times I felt uncomfortable during refactoring, but now I know it's because that I cut corners and didn't take small enough steps.

The book also "refactors to patterns" a lot, which I found helpful reading immediately after the design pattern book.
Steve Fenton
Jan 25, 2019 rated it it was amazing
What I like most about this book is that many of the refactorings are accompanied by an inverse equivalent. Like the GoF book on patterns, the idea behind the library is to commit the existence of patterns to memory, but refer back to the library when you want to apply one.
Jeroen De Dauw
Great introductory book to the topic for people not already nose deep into software design.
Nov 25, 2019 rated it really liked it
It's more like a reference than a book, so it's a bit dry to read.
Aleksander Meterko
A solid book for a developer which contains a number of so-called "code smells", which should tell you that this specific piece of code needs to be refactored, along with techniques to achieve this result. Although these techniques seems outdated as modern IDEs are able to make most of these refactorings automatically for you (and these automation is described in Chapter 14) it is still good to know when to perform these refactorings.

This book may be read both as a reference guide (it has conven
Costin Manda
Feb 27, 2019 rated it really liked it  ·  review of another edition
Shelves: owned
It was long overdue for me to read a technical book and I've decided to go for a classic from 1999 about refactoring, written by software development icons as Martin Fowler and Kent Beck. As such, it is not a surprise that Refactoring: Improving the Design of Existing Code feels a little dated. However, not as much as I had expected. You see, the book is trying to familiarize the user with the idea of refactoring, something programmers of these days don't need. In 1999, though, that was a breakt ...more
Yevgeniy Brikman
Pros: presenting refactoring as a regular part of the development process is an important step forward. The example at the start of the book is a great demonstration if why this stuff matters. Nice to systematically catalog code smells.

Cons: the code smells section is great, but has no actual code examples. The chapters that go through the refactoring moves are better, but having each one isolated makes it boring to read. The big refactoring chapters are only UML diagrams, which are not good te
Apr 18, 2012 rated it really liked it  ·  review of another edition
I was having a great time reorganizing and hopefully improving some Java at work, and a coworker had mentioned this book. Good stuff. I didn't read through the whole reference section, but took a quick look at some. It seems like the IDE I was using (IntelliJ) had a bunch of refactorings (not sure what the overlap is with this catalog) available as keyboard shortcuts, basically. But it's still fun to read about. Unfortunately, I got this book approximately the same week I shifted off Java develo ...more
May 19, 2015 rated it really liked it  ·  review of another edition
Shelves: programming
Finally finished this, long after the book club for it was over! This is a classic, which means there are both really good pieces of wisdom in here as well as concerns that don't need to be worried about so much anymore with more modern tools and text editors. The majority of the book is kind of a reference of refactoring "recipes" with checklists to go through to make sure you haven't missed something--time will tell if I end up using that reference portion. The descriptions and motivations for ...more
Mahmoud Tantawy
May 22, 2017 rated it it was amazing  ·  review of another edition
Good way to end a year!
A must-read reference for every developer, not only ones dealing with legacy code but ones starting new project to save the project on the long-run.

The book is well written, provides samples, examples, diagrams, steps to follow, side-notes, commentary, and basically everything you would need to fully understand a refactoring method.

While the book doesn't provide revolutionary solutions to perform refactoring (you shouldn't perform major refactoring in one step anyway), a l
Mar 09, 2009 rated it it was amazing  ·  review of another edition
Shelves: work
The best programming book I've read in a long time.

There are a lot of design and analysis books but not a lot of programming books. I would gladly read anything from Fowler. It's so simple of a concept but it goes against a lot of 'common sense'. Essentially, don't over design. Don't spend too much time in design and analysis that you've been told to do based on the wrong assumptions of the waterfall model (which never worked).

Kent's book on Test-driven Development is a great companion to this
Tien Nguyen Van
Sep 09, 2019 rated it really liked it  ·  review of another edition
This book can give you a motivation to start refactoring & how to do it the right way.
From my perspective, this book 70% like a catalog to look up when you have a case & need to refactor it.
I can't remember all of the patterns, but I can index it whenever I don't have any idea how to refactor it.
One more thing that around the pattern which covers by this book good focus for OOP than others. I didn't like this point too much.
Ricardo Cavalcanti
This book represents one of the building blocks of good programming. Most of the examples are in java, and most of the techniques are already implemented by IDE such as IntelliJ. Still, the ideas can be applied in any programming language, with or without an IDE.
Fernanda Martins
Feb 02, 2016 rated it really liked it  ·  review of another edition
Very dense book. There's a lot of techniques about refactoring. It's a bit intense so I recommend not reading everything at once like I did.
Simon Booth
Good in its day

This is the book that introduced the concept of refactoring to the wider software engineering community. A refactoring is a change to the structure of code that does not change its functionality. Prior to this the prevailing wisdom was "if it ain't broke don't fix it", and whilst this is still a sensible principle in general most programmers know that code can be broken even when it produces the correct output. Refactoring the code can help to fix those less tangible problems - ma
Jean Tessier
Feb 13, 2019 rated it it was amazing
Shelves: software
An update to the 1999 classic Refactoring. I still have my autographed copy of the first edition. The original used code examples in Java. This new edition uses JavaScript instead.

I followed Fowler's advice to "read the first four chapters completely, then skip-read the catalog." It's the same approach I used when I read Gerard Meszaros' xUnit Test Patterns. The initial chapters make a case for refactoring and describe the general principles. The remainder of the book is a nice catalog of specif
Scott J Pearson
I picked up this book at the wrong time. The book was so successful that a second edition is due out on November 30, 2018 (less than two weeks from now).

On the other hand, I picked up this book at the right time. At work, my project is in the midst of a refactoring project. I am in the middle of changing PHP code from modular functions to object-orientation. The aim of this transition is to enhance the scalability of the project and ease the writing of documentation. I generally like to peer "be
Ahmed Elsayed
Jan 27, 2020 rated it really liked it  ·  review of another edition
These are rather notes than a review while reading:

1. Use very descriptive names. Be consistent with your names.

2. A function should not do more than one thing.

3. SRP (Single Responsibility Principle): a class or module should have one, and only one, reason to change.

4. Stepdown rule: every function should be followed by those at the next level of abstraction (low, intermediate, advanced).

5. A long descriptive name is better than a short enigmatic name. A long descriptive name is better than a l
The bulk of this is reference, so considering it "read" means having read the first four chapters and a handful of the refactorings themselves. I had the first edition on my shelf for ages but never managed to do more than flip through it, but I wish I had. The concept of refactoring, and its closely associated principles of automatic testing, are accepted and ubiquitous enough that I took them for granted. But having their cases laid out in detail here was still very worthwhile. Inspiring, even ...more
Nicolas Cuervo
Jun 04, 2020 rated it it was amazing  ·  review of another edition
As the book itself suggests, I read the first 5 chapters as content and skipped the rest in order to know what can be found there and keep it as a reference catalog.

The book certainly introduces the topic in a clear and exemplary manner, which I believe is the best way to come about it. It serves as an introduction to refactoring, and I would, therefore, agree with such reviews that state that there isn't something "new" about it for experienced developers. However, the book never regards itself
Nathan Glenn
Apr 09, 2013 rated it it was amazing  ·  review of another edition
I'm giving this 5 stars sort of out of principle. As far as I'm concerned, I've already long ago absorbed the contents of this book just by being part of the greater developer community. There's lots of discussion about why you should refactor, how a good idea plus refactoring is better than full design up front, etc. There's a full catalog of refactorings that you can perform, with instructions on how to do them safely with a bare text editor(!). I think most of the refactorings are just built ...more
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Goodreads Librari...: Second edition is listed as a separate book 2 235 Dec 19, 2018 10:43AM  

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Martin Fowler (b. 1963) is a software engineer, Chief Scientist at ThoughtWorks, and an outspoken advocate for best practices in enterprise software design, particularly in regard to agile software development methodologies, including extreme programming. ...more

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There's something great about a paperback book: They're perfect book club choices, you can throw them in your bag and go, and they've been out in...
22 likes · 3 comments
“I’m not a great programmer; I’m just a good programmer with great habits.” 14 likes
“Whenever I have to think to understand what the code is doing, I ask myself if I can refactor the code to make that understanding more immediately apparent.” 9 likes
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