Unleashing the Power of Automated Refactoring with JDT

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Unleashing the Power of
Automated Refactoring with JDT
Law of Diversity
Distrust all claims of ONE true way!
Naresh Jain
@nashjain
http://nareshjain.com
naresh@agilefaqs.com

Plan
What and Why... Refactor?
Automated Refactoring Demo 1 with JDT
When and How... Refactor?
Automated Refactoring Demo 2 with JDT

What is Refactoring?

What is Refactoring?
A series of small steps, each of which changes the
program’s internal structure without changing its
external behaviour - Martin Fowler

What if you hear...

What if you hear...
We’ll just refactor the code to support logging

What if you hear...
Can you refactor the code so that it authenticates against LDAP instead
of Database?

What if you hear...
of Database?
We have too much duplicate code, we need to refactor the code to
eliminate duplication

What if you hear...
of Database?
This class is too big, we need to refactor it

What if you hear...
of Database?
This class is too big, we need to refactor it
In-Memory Object Caching?

Origin
Ward Cunningham and Kent Beck
Smalltalk style
Ralph Johnson at University of Illinois at Urbana-
Champaign
Bill Opdyke’s Thesis
ftp://st.cs.uiuc.edu/pub/papers/refactoring/opdyke-
thesis.ps.Z
John Brant and Don Roberts:The Refactoring Browser

Readability
Which code segment is easier to read?
Sample 1
if (date.Before(Summer_Start) || date.After(Summer_End)){
charge = quantity * winterRate + winterServiceCharge;
else
charge = quantity * summerRate;
}
Sample 2
if (IsSummer(date)) {
charge = SummerCharge(quantity);
else
charge = WinterCharge(quantity);
}

Automated Refactoring
Demo 1

How do we Refactor?
We looks for Code-Smells
Things that we suspect are not quite right or will cause us severe pain if
we do not ﬁx

2 Piece of Advice before Refactoring

Baby Steps

Baby Steps
The Hippocratic Oath
First Do No Harm!

Automated Refactoring
Demo 2

Code Smells Lab
Long Method
Lazy class and
Speculative Generality Smell
Refused Bequest
Black Sheep
Duplicate Code
Switch Smell
Dead Code
Alternative Classes with different interface
Odd Ball solution
Primitive Obsession

Why do we Refactor?

Why do we Refactor?
Helps us deliver more business value faster

Why do we Refactor?
Helps us deliver more business value faster
Improves the design of our software
Combat’s “bit rot”
Easier to maintain and understand
Easier to facilitate change
More ﬂexibility
Increased re-usability

Why do we Refactor?...

Minimizes technical debt

Keep development at speed

To make the software easier to understand
Write for people, not the compiler
Understand unfamiliar code

To help ﬁnd bugs
refactor while debugging to clarify the code

To help ﬁnd bugs
refactor while debugging to clarify the code
To “Fix broken windows” - Pragmatic Programmers

When should you refactor?

To add new functionality
refactor existing code until you understand it
refactor the design to make it simple to add

To ﬁnd bugs
refactor to understand the code

To ﬁnd bugs
For code reviews
immediate effect of code review
allows for higher level suggestions

To ﬁnd bugs
For code reviews
immediate effect of code review
allows for higher level suggestions
Like championship
snooker players we are
setting ourselves up for
our next shot

The Two Hats
Adding Function
Add new capabilities to the system
Adds new tests
Get the test working
Refactoring
Does not add any new features
Does not add tests (but may change some)
Restructure the code to remove redundancy

The Two Hats
Adding Function
Add new capabilities to the system
Adds new tests
Get the test working
Refactoring
Does not add any new features
Does not add tests (but may change some)
Restructure the code to remove redundancy
Swap frequently between the hats, but only wear one at a time

Refactoring and TDD
TDD Rhythm - Test, Code, Refactor

Refactoring and TDD
Add a Test

Refactoring and TDD
Add a Test
Run the Test

Refactoring and TDD
Add a Test
Run the Test
Pass

Refactoring and TDD
Add a Test
Run the Test
Fail
Pass

Refactoring and TDD
Add a Test
Run the Test
Make a little change
Fail
Pass

Refactoring and TDD
Add a Test
Run the Test
Run the Test
Fail
Pass

Refactoring and TDD
Add a Test
Run the Test
Run the Test
Fail
Fail
Pass

Refactoring and TDD
Add a Test
Run the Test
Run the Test
Fail
Pass
Fail
Pass

Refactoring and TDD
Add a Test
Run the Test
Run the Test
Refactor
Fail
Pass
Fail
Pass

T H A N K Y O U !
Q U E S T I O N S ?
Naresh Jain
@nashjain
http://nareshjain.com

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