1. Writing Good Code
<lecturer> Leo Liang </lecturer>
<date> 2009-7 </date>

2. We are …
Elegant Code
Programmer
Designer

3. Principles
 Your code should
– be simple and clean
– be readable and maintainable
– be testable
– be secure
– be extensible

4. Rule #1
get the job done

5. Readable
白色马驹
浮出雾中
 Beautiful code is like poem 转瞬不见
回到雾里
秋日午后
– Good code style 无花果树叶
– Meaningful naming 轻轻落下
– Short method 停在
自己的影子上
– Appropriate class size
--- 阿巴斯
 Unreadable code is unmaintainable
How To Write Unmaintainable Code?
http://freeworld.thc.org/root/phun/unmaintain.html

6. Simple & Clean
 Choose the simplest way that could
possibly work
 Don’t repeat yourself
– Reuse
 High cohesion, low coupling
– Design with contracts
– Orthogonal ( 正交 )

7. Robust
 Robustness means two things:
– getting the job done
– continuing to get the job done as much as
possible even when things go bad

8. Performance vs. Style
 Code style is more important than code performance
– Consider readability and maintainability
Clever Code
 Performance is very important
 How the design is affects performance much more
than how to code
– Performance is depends on a lot of factors
– Design correctly
– Identify the performance bottleneck by test or tool

9. Don’t live with BAD code
Refactoring

10. Principles
 Your code should
– get the job done
– be simple and clean
– be readable and maintainable
– be testable
– be secure
– be extensible

11. Coding Guidelines

12. Why need code convention
 Improve the readability
 Create maintainable code
 Eliminate potential bugs
– Bug pattern
– Best practices
 ClearCase merge
 No absolutely good or bad
 Need unify convention in a team

13. Programming Style Guidelines
 Every product line has its own guidelines defined
– SIG / ISP / MSDP / MIEP / AOP
 General guidelines
– Java Guidelines from Geotechnical Software Services (
http://geosoft.no/development/javastyle.html)
– Excepts: 8 / 20 / 34 / 61 / 63 / 64
Take 20 minutes
to go throw them!

14. Naming Convention
 Camel case
– Types: nouns
– Methods: verbs
TrafficProfile trafficProfile = createTrafficProfile();
 Constants: all uppercase using underscore to separate
words
setStatus( SERVICE_NOT_ACTIVE );

15. Comment Delete the unused code
instead of comment out
 JavaDoc
– Classes, public methods
 Comment on
– where the code isn’t easy to understand
– where the code differs to conventions
 Unfinished task
– // TODO: description
 Know issue
– // FIXME: description

16. No warning
 Target: No warning
– Everyone has the responsibility to fix the warnings
– Should check at code review
 Suppress warning (Be careful!)
– Java:
Annotate with @SuppressWarning
– CheckStyle:
Suppress audit events between a comment containing
CHECKSTYLE:OFF and a comment containing
CHECKSTYLE:ON
– FindBugs:
Edit the findbugs_exclude.xml

17. Sample
 Find code style issues from the sample code
sample.java

18. Eclipse Usage
 Eclipse built-in code style formatter
– Menu: Source – Format
– Keyboard: Ctrl-Shift-F
 Rename an identifier is very easy in Eclipse
– Menu: Refactor - Rename
– Keyboard: Alt-Shift-R

19. Code Check-in Rule
 Before check-in your code, you must ensure
– Code compiled successful
– Basic test passed
 Check-in frequency
– As soon as possible
– No longer than 1 day
 Do not leave the file locked when you are not editing it
 Write meaningful comment at check-in
Ensure the code in ClearCase is always valid

20. Quick Reference

21. Quick Reference – Naming Example
AudioSystem audioSystem; // NOT: audio_system
openDvdPlayer(); // NOT: openDVDPlayer();
getServiceCapability(); // NOT: getSc();
MAX_ITERATIONS = 25;
void setTopic(Topic topic) // NOT: void setTopic(Topic value)
// NOT: void setTopic(Topic aTopic)
// NOT: void setTopic(Topic t)
Collection<Point> points; // NOT: point
line.getLength(); // NOT: line.getLineLength();

22. Quick Reference – Naming Example
void setFound(boolean isFound);
// NOT: setIsFound(boolean isFound)
// NOT: setFound(boolean found)
boolean hasLicense, canEvaluate, shouldAbort;
get/set, add/remove, create/destroy, start/stop, insert/delete,
increment/decrement, old/new, begin/end, first/last, up/down,
min/max, next/previous, old/new, open/close, show/hide,
suspend/resume
xxxFactory, xxxProxy, xxxFacade, xxxCommand
xxxExecption, xxxImpl, DefaultXxx, AbstractXxx

23. Quick Reference - Comment
 Comment as reminder
// TODO: ……
// FIXME: ……
 Suppress warning
– Java / FindBugs / PMD
@SuppressWarning
– checkstyle
// CHECKSTYLE:OFF
Some codes …
// CHECKSTYLE:ON

24. Quick Reference - Eclipse
 Format code style
– Source - Format (Ctrl-Shift-F)
 Organize imports
– Source - Organize imports (Ctrl-Shift-O)
 Rename identify
– Refactor - Rename (Alt-Shift-R)
 Code clean up
– Source - Clean up…
 Error correct suggestion
– Edit - Quick Fix (Ctrl-1)
 More functions in Source and Refactor menu …