1. Optimize Your Java Code By Tools
NuPoint Technology Inc.
Manager of R&D Dept.
Lin, Weicheng

2. Agenda Why to Optimize Your Code? Introduction Optimize by OptimizeIt
Conclusions

3. Why to Optimize Your Code?
Why coding?
Why do your program need more execution time or developing time than that of others’?
Do you agree that Programming is an ART?

4. Introduction How to write a good program? Bad implementation
Suitable language
C++, Java, Perl, Scheme, …
Good algorithm
You need to learn Algorithm, OS, …
Good implementation
You need not only a good brain but a good tool
Bad implementation
Allocate too much memory
Instantiate too many objects
Bad programmatic logic …

5. Introduction (Cont.)
There are several tools for optimization use: OptimizeIt, …
Functions of Optimization Tools
Profiling
Code Coverage Checking
Thread Debugging
Progress Tracking
Request Analyzing

6. Optimize by OptimizeIt
The goal of the optimization
A quick introduction to the application
Application architecture
Integrating JBuilder and OptimizeIt
Optimizing your first project

7. The Goal of the Optimization
Using JBuilder and OptimizeIt to solve performance problems with an agent
A user with 4000 Messages per day
Before the performance tuning
Several minutes
After the performance tuning
< 10 seconds
Improvement
Less execution time
Less required memory

8. A Quick Introduction to the Application
Spam filtering
It deletes spam from a user's mailbox using a variety of spam-filtering rules
Forwarding of desirable messages to a pager
A user can control which messages should be forwarded from their inbox to their pager
Mail server-independence
The Agent works with any server that supports the POP-3 or IMAP standards
Platform-independence
The Agent can run on any computer platform that supports Java, making it very flexible to install

9. Application Scenario Scenario
Currently, only a user, with 4,000 messages
About 1,000 spam messages
Running every five minutes
In the need of handling more users

10. Application Architecture

11. Basic Algorithm of the Email Agent
Application startup.
Initialize logger.
Read mail server connection properties.
Read properties for sending a summary report to the user.
Initialize internal lists from configuration files.
Create and populate the Agent.
Connect to the mailbox.
Remove spam from the current folder.
Get the message list from the inbox.
Determine the UIDs of these messages.
Get a list of messages that have already been examined already.
While only looking at new messages:
One at a time, review each message to determine whether or not it is spam.
If the message matches an ``allow'' file rule, let it pass through.
Otherwise, test the From, Reply-To, and Subject fields, as well as message attachments.
If a message matches a notification criteria, send a message to my pager.
Close the mailbox and store.
Send me summary information about what actions were taken.
Be care of your for-loop!

12. Basic Configuration Configuring the application allow.from
allow.subject
allow.contents
reject.from
reject.subject
reject.contents

13. Integrating JBuilder and OptimizeIt
Installation

14. Integrating JBuilder and OptimizeIt (Cont.)

15. Optimizing Your First Project

16. Finding the Performance Problems
Java Performance Tuning'' by Jack Shirazi
Measure the performance of the application, using tools, and/or by instrumenting the code.
Identify the location of any bottlenecks.
Think of a hypothesis for the cause of the bottleneck.
Consider any factors that might refute your hypothesis.
Create a test to isolate the factor identified by the hypothesis.
Test the hypothesis.
Alter the application to reduce the bottleneck.
Test that the alteration improves the performance.
Repeat from step 1.

17. Finding the Performance Problems (Cont.)
Simplified version of the process
Instrument your code and find the major bottlenecks, using the best tools available
Fix the bottlenecks that are causing the biggest problems, don't worry about the others. If you can't fix it, avoid it
If performance is now acceptable, celebrate. If not, repeat from step 1

18. Finding the Performance Problems (Cont.)
Fix the bottlenecks that are causing the biggest problems and don't worry about the others
Simplified analysis example
examineContents() - 70%
extractContents() - 20%
parseAttachment() - 10%

19. The First Run: An Example of How to Use Avoidance Therapy

21. Drill Down Your Programmatic Flow
Using Contents needs a lot
of time
Put this line in the last
It will be run when needed

23. The Second Run
Built in JDK 

24. The Third Run: Problems with Regular Expressions
aMatcher.find() wastes too much time
indexOf is faster
Change the order!

25. aMatcher.find() is still slow, we use aMatcher.matches()
9,956 ms

27. 9,548 ms

29. Getting Harder Now
9,548 ms

30. Getting Harder Now (Cont.)
9,353 ms

31. Conclusions
Reducing the application runtime from over 52 seconds down to about 9.4 seconds
You really need a optimization tool, don’t you?
Now, do you agree that Programming is an ART?

32. Thanks!