The document discusses the importance of refactoring in software development, highlighting techniques for code improvement without altering its external behavior. It emphasizes safe refactoring practices, overcoming challenges such as legacy code, and the benefits of incremental changes and collaboration. The content also touches on common code smells and offers strategies for efficient development habits and maintaining code quality.

1. VictorRentea.ro
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victor.rentea@gmail.com ♦ ♦ @victorrentea ♦ VictorRentea.ro

2. Victor Rentea
VictorRentea.ro
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CODE

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Refactoring
What must we do every single day?
What’s that?

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Simplify existing code
without changing its external behavior
Refactoring
DO NOT BREAK
PRODUCTION

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I'm afraid to refactor
because we don't have tests
It's impossible to test a
200-lines method!
The Vicious Circle of Legacy Code
Pair Programming
(80% less bugs)
Coding Katas!
TDD Practice

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Safe Refactoring Tips
Next IDE Refactoring Fails Stress
Don't Break Compilation
(unless exploring)
Automated Refactoring
as much as you can
Decompose Large Changes
into small, safe moves
Use Quick-fix
to keep your focus on the design
(Alt-Enter / ⌥-Enter)

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Time
TIME FRAME
SPEED

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"I don't have time. I'm too busy"
Being busy is a form of laziness
- Tim Ferriss
Habits of Efficient Developers
by Daniel Lebrero
Stop! and Reflect.
Focus on what matters.

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Improve Your Focus
Turn off desktop/mobile notifications
Automate Stuff
Pomodoro 25/5
No morning inbox
Max 30 min meetings
 Digital Detox
Master your IDE ➔
Get your brain to focus
Chris Bailey
IntelliJ Productivity Tips
Victor Rentea

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Time
TIME FRAME
SPEED

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Estimates

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Emotionally Involved

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Ever-changing Requirements

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NO

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technical
functional (complex requirements)
iterations
(the point of Agile)
prototype/POC
Estimations Risks

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Time & Fear ☺

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The Best way to understand code is to Refactor it

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You lost it! You got carried away...

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3 hours later, you commit:
code improvements
refactoring
I gotta leave
Major changes

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Explore

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Exploratory Refactoring
Discover
Timeboxed: eg 15 min.
Revert.
Ctrl -
Missing from our Practice:

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refactoring idea
Long-lived Feature Branch
Source Control

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Merge Conflicts
Top annoying things in Dev's life:
➢ Interruptions
➢ Refactoring Tests
➢ Long meetings, and

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Trunk Based Development
(requires maturity & discipline)
Git Flow
(merge conflicts, redo-refactor)
Long Branches Inhibit Refactoring
if (easyBoxReturnFeature) {
// feature under develop
}
Feature Toggle
+ incremental DB migrations
Preliminary Refactoring
(separate Pull-Request)

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Micro-commits
Break a large change set into:
Large + Safe Automated Refactoring
Manual Refactoring
Adding Behavior
+ Easier Code Review + Less Bugs
- Prior Exploration Needed
to identify the steps
A Commit Message Notation: https://github.com/RefactoringCombos/ArlosCommitNotation
Separate
Commits, or
Preparatory
refactoring PR

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What Stops Refactoring: Recap
Fear
➔ tests, pair programming
➔ practice
Time
➔ Proper estimates
➔ Improve Effectiveness
Rushing
even without time pressure
Lack of Consensus
➔ team design brainstorm
Huge PR - Rejected
➔ Trust
➔ Micro-Commits
Fear of Breaking some Eggs
to make the omelet
Merge Conflicts
➔ short-lived branches
➔ trunk-based
YOLO-driven developer
A. Make it fun, play together
B. Legacy Experience TM
Lack of Skills
extract a method ?!!
➔ Learn Code Smells
Unknown Code
Refactoring = Learning

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Worse
Code
(hours-days)
Initial Chaos
Code
Quality
Time
You are here
The Deepest, most impactful refactoring starts with making a bigger mess
"You have to break some eggs
to make an omelet"
Wow!
I see a deep refactoring
eg. join two 100-lines method➔ one 200-lines method

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Worse
Code
(hours-days)
Code
Quality
Time
You are here
The Strength to Revert
(despite emotional involvement)
Ctrl-
A day without no Ctrl-Z
is a day you didn't learned anything
... and the speed to get to some conclusions fast
You need

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Code Smells
“If it stinks, change it.”
— Grandma Beck, discussing childrearing philosophy

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Large Method
God Class
Too Many Parameters
Data Clumps
(String, String, Long) ➔ Address
> 20 lines
> 200 lines
> 4
All numbers are arbitrary. Find your own comfort zone

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Enrich your Domain Language
by Discovering Value Objects
Simplify your code
Constraints Methods Reuse in larger Entities

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Speculative Generality
Middle Man
person.getAge()
int getAge() {
return bio.getAge();
}
person.getBio().getAge()
Data Classes
get/set mania ➔ OOP
Feature Envy
Function ❤️ the state of an object
Primitive Obsession
➔ PhoneNumber, OrderId, enum
➔ 💋 KISS Principle

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Primitive Obsession
Map<Long, List<Long>> customerIdToOrderIds
redeemCoupon(Long, Long, String)

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Map<Long, List<Long>> customerIdToOrderIds
Map<CustomerId, List<OrderId>> orders
redeemCoupon(Long, Long, String)
redeemCoupon(CustomerId, CouponId, PhoneNumber)
Micro-Types

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Primitive Obsession
Make concepts explicit
by introducing new small classes
Even if it's a single
String → PhoneNumber
Long → CustomerId → ID type:
@Value
class CustomerId {
Long id;
}
Escape the

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Map<Long, List<Long>> customerIdToOrderIds
If the only usage of a map is:
for (Long customerId : map.keySet()) {
List<Long> orderIds = map.get(customerId);
...
}
Code Smell: Iterating over Map Keys
List<CustomerOrderIds>
You might be missing an abstraction (class):
class CustomerOrderIds {
private Long customerId;
private List<Long> orderId;
...
}
(or entries)

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Divergent Changes
Duplicated Code
Shotgun Surgery
m()
Is it a bug or a feature?
<>
DRY SRP
Is terrible when changes

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switch
repeated switches loops
for (e : list) {
A();
B();
}
list.stream()...A..
list.stream()...B..
vs Polymorphism
vs "functional" switch in java17
vs enum with logic/Function refs

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Long-Lived
Temporary Field
x.setX(1);
x.doStuff();
out = x.getY();
Temporal Coupling
out = x.doStuff(1);
Mutable Data
+ Multi-Threading =
reads from X field
and writes to Y field

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Code Smells Sheet
Defeating the Evil starts with Naming It

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Code Smells Sheet
Defeating the Evil starts with Naming It
https://sourcemaking.com/refactoring/smells
Long Method
God Class
Data Clumps
Long Parameter List
Primitive Obsession
Data Class
Feature Envy
Middle Man
Duplicated Code
Shotgun Surgery
Divergent Code
Repeated Switches
Loops
Temporary Field
Long-Lived Mutable Data
Speculative Generality
Comments
Chapter 3
Many more + Solutions in
or: https://sourcemaking.com/refactoring/smells

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