JAVA CODING STYLE - Best practice

Hi all,
In my current j2ee related project, i have being assigned to write a utility class assume (MyUtilityClass) which will have two methods..assume methodA() and methofB().
Being it an utility class, i heard it should be only static methods and contants as final static in all utility class. Is there any rules (best practices) to write a component or an utility class in java..if yes where i can find more info on that?
and for the above requirement i am planning to have
an Interface and its impl [methods are static inside that].
Thanks in advance

Hi,
Thanks for the reply..No i dont want to maintain any state.
Actually the methods inside the class are goign to generate the checksum string for any file.
the I/p for the method will be a File and output will a String (Calculated checksum value). one method will be for 32 bits and one for 128bit..this is my scenario..
Interface ChecksumGenerator{
public static String checksum32 (File){
public static String checksum128(File){
Class ChecksumGeneratorImpl implements ChecksumGenerator{
public static String checksum32 (File){
///code
public static String checksum128 (File){
///code
}I will also have an Interface so that..in future the impl can also change..
is that the right way to do that?
by the way
in my eclipse i am going to have 4 projects
(1) ProjectPersistence
(2) ProjectWeb
(3) ProjectUtils
(4) Project Business
i am planing to have this class inside ProjectUtils
thanks in advance....

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3.System class loader
and is wondering if this has something to do with the cold start problem?
The extensions class loader loads the code in the extensions directories (<JAVA_HOME>/lib/ext
So, we should move app classes to ext? Put them in one jar file? (We have many). Best practice about that?
Otherwise it seems to me that it must be about finetuning the JVM?
I imagine that it is a question about:
1. the right heap size
2. the right garbage collection scheme
Googling heap size for XP
CHE22 writes:
You are right; -Xms1600M works well, but -Xms1700M bombs
Thats one best practice or what?
On garbage collection, there are numerous posts, and much "masters of Java black art" IMHO, And according to profiling GC is not really that much of a problem anyway? Still,
Based on my description I was hoping for a short reply like "try setting these two parameters on your xp box, it worked for me" ...or something like that. With no takers on that one, I fear people are saying that there is nothing to be gained there?
we read:
[ -Xmx3800m -Xms3800m
Configures a large Java heap to take advantage of the large memory system.
-Xmn2g
Configures a large heap for the young generation (which can be collected in parallel), again taking advantage of the large memory system. It helps prevent short lived objects from being prematurely promoted to the old generation, where garbage collection is more expensive.
Unless you have problems with pauses, try granting as much memory as possible to the virtual machine. The default size (64MB) is often too small.
Setting -Xms and -Xmx to the same value increases predictability by removing the most important sizing decision from the virtual machine. On the other hand, the virtual machine can't compensate if you make a poor choice.
The -XX:+AggressiveHeap+ option inspects the machine resources (size of memory and number of processors) and attempts to set various parameters to be optimal for long-running, memory allocation-intensive jobs]
So is Setting -Xms and -Xmx and -XX:AggressiveHeap
best practice? What kind of performance improvement should we expect?
Concerning JIT:
I read this one
[the impact of the JIT compiler is obvious on the graph: at startup the time taken is around 500us for the first few values, then quickly drops to 130us, before falling again to 70us, where it stays for 30 minutes,
for this specific issue, I greatly improved my performances by configuring another VM argument: I set -XX:CompileThreshold=50]
The size of the cache can be changed with
-Xmaxjitcodesize
This sounds like you should do something with JIT args, but reading
// We disable the JIT during toolkit initialization. This
// tends to touch lots of classes that aren't needed again
// later and therefore JITing is counter-productiive.
java.lang.Compiler.disable();
However, finding
the sweet spots for compilation thresholds has been tricky, so we're
still experimenting with the recompilation policy. Work on it
continues.
sounds like there is no such straigth forward path, it all depends...
Ok, its good, when
[Small methods that can be more easily analyzed, optimized, and inlined where necessary (and not inlined where not necessary). Clearly delineated uses of data so that usage patterns and lifetimes are apparent. ]
but when I read this:
[The virtual machine is responsible for byte code execution, storage allocation, thread synchronization, etc. Running with the virtual machine are native code libraries that handle input and output through the operating system, especially graphics operations through the window system. Programs that spend significant portions of their time in those native code libraries will not see their performance on HotSpot improved as much as programs that spend most of their time executing byte codes.]
I have the feeling that we might not able to improve performance that way?
Any comments?
otherwise i was wondering about
-XX:CompileThreshold=50 -Xmaxjitcodesize (large, how large?)
Somehow, we still feel that someone out there should have experienced similiar problems? But obviously there is no guarantee that the someone should surf by here!
In c++ we used to just write everything ourselves. Here it does seem to be a question about the right use of other peoples stuff?
Where you are kind of hoping for a shortcut, so you dont have to read endless number of documents, but can find a short document that actually addresses your problem ... well.
-Simon
Edited by: simoncpm on Mar 15, 2010 3:43 PM
Edited by: simoncpm on Mar 15, 2010 3:53 PM

JAVA CODING STYLE - Best practice

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