CDC HotSpot Implementation...

Hi all,
first I apalogize for my bad english ;)
I'm new in developing in J2ME (CDC/PP), and I just downloaded CDC Hotspot implementation and Sun's Personal Profile Implementation (also providing CDC) on Sun's website. I've allready been able tu run some applications using this on my laptop and on my desktop station (using Ubuntu). But by now I wonder how using it on PDA's.
I have to develop a thin client for VoIP that need to run on both thin clients and desktop stations. I prefer testing my applications part step by step on both stations, that's why I'm wondering how to port CDC on my PDA.
If anyone has any idea, I'll happy to hear about ;)
If anyone also have some idea about good things or sample code to use to develop VoIP on PDA's I'll also be greatfull.
Thanks,
David (Belgium)

I don't know if this is what you are asking for, but if you want to install the runtime, you have to copy the .cab file to your Windows Mobile device, and run it there... It will install... however, I still don't know how to install or copy your own program there... when you open the program, an empty screen appears and there is no menu to intall applications....
I hope this helps you a bit...

Similar Messages

Cdc hotspot implementation for ixp425

Hello,
Is there any CDC hotspot implementation or any jvm available for ixp4xx(ARM/XScale) line of network processors. Thanks in advance.
with regards,
Pr@k@sh

Hi Alex
I'm also interested in your exact question. Any information since your post?
Thanks
Sherine

CDC HotSpot on PocketPC ?

Has anyone seen this page?
http://java.sun.com/products/cdc-hi/
I'm not sure if I'm reading it correctly, but does that mean there's a CDC VM for PocketPC OS put out by Sun? I sent an email to Sun asking for clarification and licensing.
Has anyone else used / licensed this?
Thanks,
-Alex

Hi Alex
I'm also interested in your exact question. Any information since your post?
Thanks
Sherine

InPlace execution in CLDC hotspot implementation

I am working on Inplace execution feature given by SUN in CLDC Hot spot Implementaion. I want to know how much performance can be increased by using inplace execution for the midlet to be run on the device. I have converted the midlet jar file into application image (bun) but not able to know whether I have got any significant improvement or not.
Can anybody tell me that how can inplace execution improve the performance and it will affect which part? Is there any way to know how much performance has been increased like some benchmark midlet for InPlace Execution feature.
Please provide some help.

This type of emulation is called HLE, there are some drawbacks to this approch. The one that i think prevented implementors of an VM to go this road is that it's verry hard to compile all bytecode to native code and be sure there are no security problems. Also the general protection failts will come to your java code! Of cause this can be prevented by putting in a lot of overhead code for every bytecode instruction, but then it's not fast anymore! ;o)

Java ME - JRE distributed with SDK 3.0

Hi,
What I want to do is to develop a program which is based on CDC 1.1 with PBP 1.1 and AGUI optional package.
I just downloaded the new Java ME platform SDK 3.0 EA. Its specification is saying that the SDK is coming with a runtime environment for windows mobile devices. After checking the manuals corresponding to Java ME, I found out that the Java CDC Hotspot Implementation (cdc-hi) is the JVM which I have to use. Checking the folder structure in the new SDK there is a folder "runtimes", containing the subfolders "cdc-hi" and "cldc-hi". By now the problem I have is that I absolutely don't know how to install the runtime environment (which is actually distributed with the new SDK) on a mobile device. Furthermore, I'm not sure if it is only a runtime environment or emulator for CLDC configurations.
I hope you can help me out!

I don't know if this is what you are asking for, but if you want to install the runtime, you have to copy the .cab file to your Windows Mobile device, and run it there... It will install... however, I still don't know how to install or copy your own program there... when you open the program, an empty screen appears and there is no menu to intall applications....
I hope this helps you a bit...

Obtain CDC + Foundation Profile

Hi,
Where can I get CDC + Foundation Profile HotSpot Implementation?
For CDC (FP) reference inplementation, does it only support Linux platform?
Thanks very much,

Just do export LANG=en_US
also edit the /etc/sysconfig/i18n file entry for LANG to en_US instead of the UTF.8 stuff
I don't know the exact reason though.. this will work.
--Prasanna Kumar

TCK 1.1 File tests fail against CDC-HI-1.1.1-rr-b6

Dear All,
Am doing xscale build of CDC-HI-1.1.1-rr-b6 and am running TCK 1.1 against it on a montavista 3.1 platform . Out of 9102 , about 320 tests fail. All the optional packages have been built with the hotspot implementation. The File section of the java_io tests all fail with the harness version 3.2_02 fcs b05 giving the error that
Directory CDC-TCK-1.1/CDC-TCK_11/tests/api/java_io/File not found. Possible configuration Error
and all File related tests fail. Other tests that fail are FileDescriptor, FileInputStream, FileNotfoundException,File OutputStream, Filereader,FileWriter,OutputStreamWriter, Serialization components .
I can for sure see that the File directory exists in java_io dir and the file->serial tests also pass. Any pointers if am missing any enviornment vars or testing with wrong TCK version ?
regards
Manav

Dear All,
Even i am facing the same problem.
Getting "Possible configuration Error" for java_io tests.
Help required!!!
Thanks in Advance.
Thanks and Regards,
Deepraj

CDC-TCK1.1 File tests fails against CDC-HI-1.1.1-rr-b36

Dear All,
Am doing xscale build of CDC-HI-1.1.1-rr-b6 and am running TCK 1.1 against it . Out of 9102 , about 320 tests fail. All the optional packages have been built with the hotspot implementation. The File section of the java_io tests all fail with the harness version 3.2_02 fcs b05 giving the error that
Directory CDC-TCK-1.1/CDC-TCK_11/tests/api/java_io/File not found. Possible configuration Error
and all File related tests fail. Other tests that fail are FileDescriptor, FileInputStream, FileNotfoundException,File OutputStream, Filereader,FileWriter,OutputStreamWriter, Serialization components .
I can for sure see that the File directory exists in java_io dir and the file->serial tests also pass. Any pointers if am missing any enviornment vars or testing with wrong TCK version ?
regards
Manav

Dear All,
Even i am facing the same problem.
Getting "Possible configuration Error" for java_io tests.
Help required!!!
Thanks in Advance.
Thanks and Regards,
Deepraj

Difficult to get personal hotspot working, need 10 retries!

The hotspot creation from OSX was the main reason I upgraded to Yosemite. But for some reason, on my system. It would not always work. When I click on it from OSX's wifi menu, it will attempt to connect (with the rings flashing) but it then it would error out. To get it to work, I usually have to keep hitting over 10 times, and eventually it might work. How do I fix this?

Turn off you Wifi everywhere and try the following:
I found a solution to USB tethering problems since recent firmware upgrades and share that here in case anyone else is having the same issue:
Since the introduction of the firmware update 4.3.2 or somewhere thereabouts, and personal hotspot implementation, "Tether using USB" has disappeared from the menu.
Semantically, where they've put it makes no sense (except financially, from forcing frustrated former users of USB tethering to use the wifi personal hotspot, forget, and rack up data charges with their carriers) - USB tethering is hiding under "Personal Hotspot" and the listed instructions don't work unless certain conditions are met. The iPhone shows up as a digital camera only under My Computer in Windows 7 until I follow the list below.
Here's how I got it to work today. There may be better ways and you may not need to take all steps but if you're like me you just want to get it working and carry on.
Solution: (assuming your iPhone is plugged in via USB, and Personal Hotspot is OFF (under Network | Personal Hotspot, and you're not connected to the Internet any other way....
0.     Close iTunes if it's open
1.    Turn Wifi off on your laptop
2.     Turn Wifi off on your iPhone
3.     Go into the Network | Personal Hotspot menu and turn P.H. on.
4.     I get a dialog querying whether I want to turn Wifi on, or to use USB or Bluetooth. Choose the second option
5.     Wait a little bit and it should find the device correctly and connect you to the internet. Verify with a web page.
Feel free to update or eliminate the list above and the assumptions but there you go, it works.
-Ian

Need help: Unable to tether, personal hotspot settings are ON

Was hoping to see if I can get a solution here. Network service provider couldn't fix it.
1. tethering is enabled for the network I'm on.
2. My "Personal Hotspot" is on.
3. iPhone plugged in via USB
4. iTunes is running.
Unfortunately, it doesn't tether automatically like how it should. It's just not happening. I tried looking under the Network services and can't find the network to connect to.
Tethering used to work before I made the iOS 4.3 update, now it's not. Was wondering if any of you are having the same issue here? Or have a solution for this.

Turn off you Wifi everywhere and try the following:
I found a solution to USB tethering problems since recent firmware upgrades and share that here in case anyone else is having the same issue:
Since the introduction of the firmware update 4.3.2 or somewhere thereabouts, and personal hotspot implementation, "Tether using USB" has disappeared from the menu.
Semantically, where they've put it makes no sense (except financially, from forcing frustrated former users of USB tethering to use the wifi personal hotspot, forget, and rack up data charges with their carriers) - USB tethering is hiding under "Personal Hotspot" and the listed instructions don't work unless certain conditions are met. The iPhone shows up as a digital camera only under My Computer in Windows 7 until I follow the list below.
Here's how I got it to work today. There may be better ways and you may not need to take all steps but if you're like me you just want to get it working and carry on.
Solution: (assuming your iPhone is plugged in via USB, and Personal Hotspot is OFF (under Network | Personal Hotspot, and you're not connected to the Internet any other way....
0.     Close iTunes if it's open
1.    Turn Wifi off on your laptop
2.     Turn Wifi off on your iPhone
3.     Go into the Network | Personal Hotspot menu and turn P.H. on.
4.     I get a dialog querying whether I want to turn Wifi on, or to use USB or Bluetooth. Choose the second option
5.     Wait a little bit and it should find the device correctly and connect you to the internet. Verify with a web page.
Feel free to update or eliminate the list above and the assumptions but there you go, it works.
-Ian

Forcing/guiding hotspot to compile sections of code

Anyone has any trick to (predictably) force hotspot to compile
a critical section of code.
I basically have an algorithm (approx 100 lines) where 80% of
cycles are spent but somehow the hotspot implementation
on Symbian/ARM (J2SE/MIDP) only hava around 30% chance of
compiling.
The result is very unpredicatble preformance.
The hotspot on PC J2SE is good of course. But that's the PC.
Anyone has any pointers?
Thanks in advance.
Cheers...

Sadly there is really nothing you dan do here. The Jit works on the background, and the application does not have any control over it.
You might try a System.gc() before you start your algo to make sure the vm cleans up a bit, but I don't think it will help you very much...

Can CDC (Change Data Capture) Can be used for Audit / Trail Purposes

Hi,
My question is bit subjective in nature. I playing around with CDC to implement a Database Auditing solution and it's seems to be working fine. However my question is for experts and for those who have already used CDC for this purpose. Is it feasible to
use it for Data Auditing? Has anybody successfully used it? Any important considerations or configurations you have worked out e.g. CDC cleanup time etc
I will highly appreciate any feed back.
Thanks,
Ali
Saadat

Refer this link...I hope this link will answer all your questions
http://blogs.technet.com/b/josebda/archive/2009/03/24/sql-server-2008-change-tracking-ct-and-change-data-capture-cdc.aspx
-Prashanth

Cdc in same process

Hi,
i wan't to hte cdc hotspot virtual machine to run in the same process as my applicaction (may be in a differente thread). In J2SE I can link my programm against libjvm.so, and then create a VM with the CreateJavaVM.
Is there a similar way to do this with the CDC version?

OK, I'm sorry, my language wasn't at the top.
My JAVA application launch external programs with the method Runtime.getRuntime().exec(...). I want to launch Internet 'Navigator' (IE, Netscape Navigator, Opera, ...), for opening URL, but I want to open several URL in a same window, so in the same 'navigator'.
Can i use the Process Class returned by the Runtime Class or do you know other ways to make what i want ?
Thanks

HP-UX vs. NT performace issue

I have a J2EE application that I've recently ported from a WINNT development box
to a 2-CPU HP L-class server. I am running Weblogic 6.1, SP1 on both machines.
On a particularly memory-intensive piece of the application, I've notice a performance
drop of 50% to 75% from the NT box to the HP box.
Each server is running the JDK 131 (w/Hotspot) that comes with the Weblogic install.
I have set all the HP system variables (max_thread_proc, etc.) to Bea recommendations.
To benchmark I used an XML->PDF engine (Apache's FOP) to render a 200 page PDF
document from a static XML-file. No database connection is involved. Below are
the results I see. Initial heap size=max heap size in each case.
HP server (HP-Unix, 2x550 mhz, 2GB ram):
Heap Size=64M, 1 report = 545ms/page (frequent out of memory errors)
Heap Size=64M, 2 reports = didn't try
Heap Size=256M, 1 report = 372ms/page
Heap Size=256M, 2 reports = 1700ms/page
Heap Size=512M, 1 report = 350ms/page
Heap Size=512M, 2 reports = 1675ms/page
Nt dev box (NT4-Worksatation, PIII-933mhz, 512MB ram):
Heap Size=64M, 1 report = 251ms/page
Heap Size=64M, 2 reports = 750ms/page
Heap Size=256M, 1 report = 245ms/page
Heap Size=256M, 2 reports = 500/page
Does this kind of perfomance gap seem normal? I can see a drop in speed due to
the processors. But two reports at once should be faster on the HP box right?
It seems sometimes Weblogic switches over to two processors, but not usually until
I run 3 or more reports at once.
The only difference I can see for sure between the two boxes is that the NT machine
performs at least 10 times as much garbage collection. (Sometimes several times
per page, as opposed to once every 8-10 pages on the NT box.) Garbage collection
occurs a little more frequenly on the HP box when I lower the heap size, but still
not nearly as often as on the NT--at any heap size. Also the HP box runs out of
memory if I lower the heap size.
Is this just some difference in the hotspot implementations? Tomorrow we are going
to try installing the HP-UX native jdk131 from Sun and pointing to that instead
of the Weblogic jdk. But I have a feeling they are the same.
If anyone has any ideas about how I can boost the performance on the HP box, or
what might be causing this gap, I'd be appreciate hearing them very much.
Thanks a lot,
Matt Savino
Quest Diagnostics

Thanks Mike. You were right, I meant to say "once every 8-10 pages on the HP box".
The thing that really bugs me is how much more the HP box degrades when I run
two reports concurrently.
And we are bent on using HP because it is a Corporate Standard. Amen.
So are you saying that JVMs run better on Windows, Solaris, or other forms of
Unix?. I'd be very interested in hearing any general opinions on this.
thx,
Matt Savino
"Mike Reiche" <[email protected]> wrote:
>
Yup, the NT box is faster, looks pretty normal to me. More concurrent
requests
(10+) might be a bit of an equalizer. Why are you bent on using HP?
Your comments regarding who does more garbage collection are not clear
- I think
you wrote 'once every 8-10 pages on the NT box' when you meant HP. I
think you're
saying that the NT box performs more GC than the HP box.
Mike
"Matt Savino" <[email protected]> wrote:
I have a J2EE application that I've recently ported from a WINNT development
box
to a 2-CPU HP L-class server. I am running Weblogic 6.1, SP1 on both
machines.
On a particularly memory-intensive piece of the application, I've notice
a performance
drop of 50% to 75% from the NT box to the HP box.
Each server is running the JDK 131 (w/Hotspot) that comes with the Weblogic
install.
I have set all the HP system variables (max_thread_proc, etc.) to Bea
recommendations.
To benchmark I used an XML->PDF engine (Apache's FOP) to render a 200
page PDF
document from a static XML-file. No database connection is involved.
Below are
the results I see. Initial heap size=max heap size in each case.
HP server (HP-Unix, 2x550 mhz, 2GB ram):
Heap Size=64M, 1 report = 545ms/page (frequent out of memory errors)
Heap Size=64M, 2 reports = didn't try
Heap Size=256M, 1 report = 372ms/page
Heap Size=256M, 2 reports = 1700ms/page
Heap Size=512M, 1 report = 350ms/page
Heap Size=512M, 2 reports = 1675ms/page
Nt dev box (NT4-Worksatation, PIII-933mhz, 512MB ram):
Heap Size=64M, 1 report = 251ms/page
Heap Size=64M, 2 reports = 750ms/page
Heap Size=256M, 1 report = 245ms/page
Heap Size=256M, 2 reports = 500/page
Does this kind of perfomance gap seem normal? I can see a drop in speed
due to
the processors. But two reports at once should be faster on the HP box
right?
It seems sometimes Weblogic switches over to two processors, but not
usually until
I run 3 or more reports at once.
The only difference I can see for sure between the two boxes is that
the NT machine
performs at least 10 times as much garbage collection. (Sometimes several
times
per page, as opposed to once every 8-10 pages on the NT box.) Garbage
collection
occurs a little more frequenly on the HP box when I lower the heap size,
but still
not nearly as often as on the NT--at any heap size. Also the HP boxruns
out of
memory if I lower the heap size.
Is this just some difference in the hotspot implementations? Tomorrow
we are going
to try installing the HP-UX native jdk131 from Sun and pointing to that
instead
of the Weblogic jdk. But I have a feeling they are the same.
If anyone has any ideas about how I can boost the performance on the
HP box, or
what might be causing this gap, I'd be appreciate hearing them verymuch.
Thanks a lot,
Matt Savino
Quest Diagnostics

Web service and ejp enterprise in JBoss

Is Java a compiled language?
Actually, Java is a compiled/interpreted language. See the links below. This is the best classification for the Java language, in my opinion. Read [_this thread_|http://forums.sun.com/thread.jspa?threadID=5320643&start=0&tstart=0] and give your opinion, too! You are very welcome in this interesting discussion. The more I participate in this forum, the more I learn. The more you participate the more you learn, too! Thank you very much for this forum, Sun!
[_CLDC HotSpot Implementation Architecture Guide Chapter 10_|http://java.sun.com/javame/reference/docs/cldc-hi-2.0-web/doc/architecture/html/VFP.html]
+The 1.1.3 release of CLDC HotSpot Implementation included limited VFP support. This feature was supported only when running in interpreted mode. In this release, full vector floating point support is provided when the virtual machine is running in compiled mode.+
[_Java Virtual Machines_|http://java.sun.com/j2se/1.4.2/docs/guide/vm/index.html]
+Adaptive compiler - Applications are launched using a standard interpreter, but the code is then analyzed as it runs to detect performance bottlenecks, or "hot spots". The Java HotSpot VMs compile those performance-critical portions of the code for a boost in performance, while avoiding unnecessary compilation of seldom-used code (most of the program). The Java HotSpot VMs also usesthe adaptive compiler to decide, on the fly, how best to optimize compiled code with techniques such as in-lining. The runtime analysis performed by the compiler allows it to eliminate guesswork in determining which optimizations will yield the largest performance benefit.+
[_CLDC HotSpot Implementation Architecture Guide Chapter 4_|http://java.sun.com/javame/reference/docs/cldc-hi-2.0-web/doc/architecture/html/DynamicCompiler.html]
+Two different compilers are contained in the CLDC HotSpot Implementation virtual machine: an adaptive, just-in-time (JIT) compiler and an ahead-of-time compiler. The JIT compiler is an adaptive compiler, because it uses data gathered at runtime to decide which methods to compile. Only the methods that execute most frequently are compiled. The other methods are interpreted by the virtual machine.+
[_Java Tuning White Paper_|http://java.sun.com/performance/reference/whitepapers/tuning.html]
+One of the reasons that it's challenging to measure Java performance is that it changes over time. At startup, the JVM typically spends some time "warming up". Depending on the JVM implementation, it may spend some time in interpreted mode while it is profiled to find the 'hot' methods. When a method gets sufficiently hot, it may be compiled and optimized into native code.+
[_Frequently Asked Questions About the Java HotSpot VM_|http://java.sun.com/docs/hotspot/HotSpotFAQ.html]
+Remember how HotSpot works. It starts by running your program with an interpreter. When it discovers that some method is "hot" -- that is, executed a lot, either because it is called a lot or because it contains loops that loop a lot -- it sends that method off to be compiled. After that one of two things will happen, either the next time the method is called the compiled version will be invoked (instead of the interpreted version) or the currently long running loop will be replaced, while still running, with the compiled method. The latter is known as "on stack replacement", or OSR.+
[_Java Technology Fundamentals Newsletter Index - Making Sense of the Java Classes & Tools: Collection Interfaces, What's New in the Java SE 6 Platform Beta 2, and More_|http://java.sun.com/mailers/newsletters/fundamentals/2006/July06.html]
+Java: A simple, object-oriented, network-savvy, interpreted, robust, secure, architecture neutral, portable, high- performance, multithreaded, dynamic language.+
[_Introduction to scripting in Java, Part 1_|http://www.javaworld.com/javaworld/jw-07-2007/jw-07-awscripting1.html?page=2]
+Many of today's interpreted languages are not interpreted purely. Rather, they use a hybrid compiler-interpreter approach, as shown in Figure 1.3.+
+In this model, the source code is first compiled to some intermediate code (such as Java bytecode), which is then interpreted. This intermediate code is usually designed to be very compact (it has been compressed and optimized). Also, this language is not tied to any specific machine. It is designed for some kind of virtual machine, which could be implemented in software. Basically, the virtual machine represents some kind of processor, whereas this intermediate code (bytecode) could be seen as a machine language for this processor.+
+This hybrid approach is a compromise between pure interpreted and compiled languages, due to the following characteristics:+
Because the bytecode is optimized and compact, interpreting overhead is minimized compared with purely interpreted languages.
The platform independence of interpreted languages is inherited from purely interpreted languages because the intermediate code could be executed on any host with a suitable virtual machine.
Lately, just-in-time compiler technology has been introduced, which allows developers to compile bytecode to machine-specific code to gain performance similar to compiled languages. I mention this technology throughout the book, where applicable.
[_Compiled versus interpreted languages_|http://publib.boulder.ibm.com/infocenter/zoslnctr/v1r7/index.jsp?topic=/com.ibm.zappldev.doc/zappldev_85.html]
Assembler, COBOL, PL/I, C/C++ are all translated by running the source code through a compiler. This results in very efficient code that can be executed any number of times. The overhead for the translation is incurred just once, when the source is compiled; thereafter, it need only be loaded and executed.
Interpreted languages, in contrast, must be parsed, interpreted, and executed each time the program is run, thereby greatly adding to the cost of running the program. For this reason, interpreted programs are usually less efficient than compiled programs.
+Some programming languages, such as REXX and Java, can be either interpreted or compiled.+

Is Java a compiled language?
Actually, Java is a compiled/interpreted language. See the links below. This is the best classification for the Java language, in my opinion. Read [_this thread_|http://forums.sun.com/thread.jspa?threadID=5320643&start=0&tstart=0] and give your opinion, too! You are very welcome in this interesting discussion. The more I participate in this forum, the more I learn. The more you participate the more you learn, too! Thank you very much for this forum, Sun!
[_CLDC HotSpot Implementation Architecture Guide Chapter 10_|http://java.sun.com/javame/reference/docs/cldc-hi-2.0-web/doc/architecture/html/VFP.html]
+The 1.1.3 release of CLDC HotSpot Implementation included limited VFP support. This feature was supported only when running in interpreted mode. In this release, full vector floating point support is provided when the virtual machine is running in compiled mode.+
[_Java Virtual Machines_|http://java.sun.com/j2se/1.4.2/docs/guide/vm/index.html]
+Adaptive compiler - Applications are launched using a standard interpreter, but the code is then analyzed as it runs to detect performance bottlenecks, or "hot spots". The Java HotSpot VMs compile those performance-critical portions of the code for a boost in performance, while avoiding unnecessary compilation of seldom-used code (most of the program). The Java HotSpot VMs also usesthe adaptive compiler to decide, on the fly, how best to optimize compiled code with techniques such as in-lining. The runtime analysis performed by the compiler allows it to eliminate guesswork in determining which optimizations will yield the largest performance benefit.+
[_CLDC HotSpot Implementation Architecture Guide Chapter 4_|http://java.sun.com/javame/reference/docs/cldc-hi-2.0-web/doc/architecture/html/DynamicCompiler.html]
+Two different compilers are contained in the CLDC HotSpot Implementation virtual machine: an adaptive, just-in-time (JIT) compiler and an ahead-of-time compiler. The JIT compiler is an adaptive compiler, because it uses data gathered at runtime to decide which methods to compile. Only the methods that execute most frequently are compiled. The other methods are interpreted by the virtual machine.+
[_Java Tuning White Paper_|http://java.sun.com/performance/reference/whitepapers/tuning.html]
+One of the reasons that it's challenging to measure Java performance is that it changes over time. At startup, the JVM typically spends some time "warming up". Depending on the JVM implementation, it may spend some time in interpreted mode while it is profiled to find the 'hot' methods. When a method gets sufficiently hot, it may be compiled and optimized into native code.+
[_Frequently Asked Questions About the Java HotSpot VM_|http://java.sun.com/docs/hotspot/HotSpotFAQ.html]
+Remember how HotSpot works. It starts by running your program with an interpreter. When it discovers that some method is "hot" -- that is, executed a lot, either because it is called a lot or because it contains loops that loop a lot -- it sends that method off to be compiled. After that one of two things will happen, either the next time the method is called the compiled version will be invoked (instead of the interpreted version) or the currently long running loop will be replaced, while still running, with the compiled method. The latter is known as "on stack replacement", or OSR.+
[_Java Technology Fundamentals Newsletter Index - Making Sense of the Java Classes & Tools: Collection Interfaces, What's New in the Java SE 6 Platform Beta 2, and More_|http://java.sun.com/mailers/newsletters/fundamentals/2006/July06.html]
+Java: A simple, object-oriented, network-savvy, interpreted, robust, secure, architecture neutral, portable, high- performance, multithreaded, dynamic language.+
[_Introduction to scripting in Java, Part 1_|http://www.javaworld.com/javaworld/jw-07-2007/jw-07-awscripting1.html?page=2]
+Many of today's interpreted languages are not interpreted purely. Rather, they use a hybrid compiler-interpreter approach, as shown in Figure 1.3.+
+In this model, the source code is first compiled to some intermediate code (such as Java bytecode), which is then interpreted. This intermediate code is usually designed to be very compact (it has been compressed and optimized). Also, this language is not tied to any specific machine. It is designed for some kind of virtual machine, which could be implemented in software. Basically, the virtual machine represents some kind of processor, whereas this intermediate code (bytecode) could be seen as a machine language for this processor.+
+This hybrid approach is a compromise between pure interpreted and compiled languages, due to the following characteristics:+
Because the bytecode is optimized and compact, interpreting overhead is minimized compared with purely interpreted languages.
The platform independence of interpreted languages is inherited from purely interpreted languages because the intermediate code could be executed on any host with a suitable virtual machine.
Lately, just-in-time compiler technology has been introduced, which allows developers to compile bytecode to machine-specific code to gain performance similar to compiled languages. I mention this technology throughout the book, where applicable.
[_Compiled versus interpreted languages_|http://publib.boulder.ibm.com/infocenter/zoslnctr/v1r7/index.jsp?topic=/com.ibm.zappldev.doc/zappldev_85.html]
Assembler, COBOL, PL/I, C/C++ are all translated by running the source code through a compiler. This results in very efficient code that can be executed any number of times. The overhead for the translation is incurred just once, when the source is compiled; thereafter, it need only be loaded and executed.
Interpreted languages, in contrast, must be parsed, interpreted, and executed each time the program is run, thereby greatly adding to the cost of running the program. For this reason, interpreted programs are usually less efficient than compiled programs.
+Some programming languages, such as REXX and Java, can be either interpreted or compiled.+

CDC HotSpot Implementation...

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