The document discusses the journey towards automatic Java refactoring, emphasizing the importance of refactoring for improving code quality, maintainability, and performance. It highlights typical problems in existing code, the human approach to refactoring, and the role of automated tools like Jsparrow, addressing technical debt and enhancing developer efficiency. The presentation concludes with the benefits and challenges of implementing automatic refactoring tools within the development process.

1. A journey to automatic Java refactoring
Software Quality Days 2019
Martin Huter & Ardit Ymeri
A journey to automatic Java
refactoring (and jSparrow)

2. A journey to automatic Java refactoring
Who are we?
Slide 2

3. A journey to automatic Java refactoring
Agenda
▪ Refactoring
▪ Software aiding the refactoring process
▪ Creating an automatic refactoring tool
Slide 3

4. A journey to automatic Java refactoring
Management: Do we really need that?
Refactoring
Slide 4

5. A journey to automatic Java refactoring
What is Refactoring
Slide 5
▪ Changing the code and keeping functionality
▪ Reasons include
▪ Improve readability
▪ Reduce complexity
▪ Improve maintainability
▪ Improve internal architecture
▪ Improve performance
▪ Improve security
▪ Parallelization

6. A journey to automatic Java refactoring
Typical Problems
▪ Design and code structure
▪ Lack of Cohesion
▪ Tight Coupling
▪ Repeated Code
▪ Spaghetti Code
▪ Lack of Performance
▪ Lack of Tests
▪ Security Issues
Slide 6

7. A journey to automatic Java refactoring
Human Approach
▪ Define a goal
▪ Understand the code base
▪ Set up a safety net - Tests!
▪ Refactor
▪ Go with baby steps
▪ Test
▪ Does everything still work?
▪ Repeat
Slide 7
Refactor
Test

8. A journey to automatic Java refactoring
Preserving Functionality
▪ Testing helps - but never guarantees.
▪ Program Equivalence
▪ Do programs P and Q terminate on the same state when starting on the same
one?
▪ Reducible to the Halting Problem.
▪ Undecidable!!!
▪ All nontrivial semantic properties are undecidable 👉 Rice’s Theorem
▪ The good news: Undecidable only in general!
▪ Show correctness for specific cases
▪ Trivial properties are decidable.
Slide 8

9. A journey to automatic Java refactoring
Using Functional Interfaces
Slide 9
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
passwordField.requestFocusInWindow();
passwordField.requestFocus();
}
});
SwingUtilities.invokeLater(() -> {
passwordField.requestFocusInWindow();
passwordField.requestFocus();
});

10. A journey to automatic Java refactoring
Using Standard Outputs
Slide 10
System.err.println(e.getMessage());
logger.error(e.getMessage());
e.printStackTrace();
logger.error(e.getMessage(), e);

11. A journey to automatic Java refactoring
Cognitive Complexity
Slide 11
public void remapIds() {
Attribute idAttribute = getAttributes();
if (idAttribute != null) {
// very long code
…
}
}
public void remapIds() {
Attribute idAttribute = getAttributes();
if (idAttribute == null) {
return;
}
// very long code
…
}

12. A journey to automatic Java refactoring
Other Code Smells
Slide 12
▪ Methods should not be empty
▪ Deprecated code should be removed
▪ Sections of code should not be commented out
@Deprecated
public static void doSomething(Object changeMe) {
// throw new UnsupportedOperationException();
}

13. A journey to automatic Java refactoring
There is Software that might help
Help me?
Slide 13

14. A journey to automatic Java refactoring
Assessing Technical Debt
Slide 14
▪ Existing Solutions
▪ Integration in development process
▪ Reporting technical debt
▪ Evaluating efforts

15. A journey to automatic Java refactoring
Addressing Technical Debt
Common scenarios for 100k lines
▪ 10s Thousands issues
▪ Hundreds working days
Addressing by:
▪ Avoid creating more debt
▪ Continuously removing debt
▪ Automatically resolving issues
Slide 15

16. A journey to automatic Java refactoring
Resolving Automatically
▪ Spotting issues
▪ Generating refactored code
▪ Avoiding Conflicts
▪ Preserving Functionality
▪ Test automation
▪ Preserving Comments
Slide 16

17. A journey to automatic Java refactoring
From Spotting to fixing
Can I automate that?
Slide 17

18. A journey to automatic Java refactoring
Change source with AST
Slide 18
1
Parsing
source
to
AST
Firstyou
need
a
toolthatw
illparse
your
source
code
like
a
com
piler
2
M
anipulating
AST
Use
the
resulting
AST
to
adoptthe
code
and
apply
fixes
3
Assure
syntax
stillvalid
Verify
changes
resultin
a
valid
source
code
4
W
riting
Changes
Apply
the
changes
to
the
source
file
and
replace
it

19. A journey to automatic Java refactoring
What framework to use?
Slide 19
Java Grammar Java Compiler Advantages of the Framework
● Open source
● Integrated within Eclipse IDE
1 Eclipse JDT
● Open source
● Integrated within Intellij IDE
2 Javaparser.org
● Mostly independent
● Building a lot from scratch
3 Antlr 4

20. A journey to automatic Java refactoring
jSparrow
Slide 20
Eclipse JDT
Eclipse Plugin
GitHub App
Maven Plugin

21. A journey to automatic Java refactoring
Automatic Refactoring
● Pros
+ Save time
+ Reduce debt
+ Set standards
+ Integration in development process
+ Improve coding habits
● Cons
- Technical restrictions
Slide 21

22. A journey to automatic Java refactoring
jSparrow Features
▪ 53 Rules and growing
▪ Custom rule profiles
▪ Portable between platforms
▪ Built-in review functionality
Slide 22

23. A journey to automatic Java refactoring
The end
▪ Thanks for your time, we now got some time left to discuss
questions.
▪ You can also visit us at our booth at number 13
Slide 23