But you still just gave me a great idea: I will design a beer based air conditioner ( air cooler ) and sell it/publish it on sites similar to engadget;-)))
Put in 4 cases of 24 and have some mechanism opening them one by one coupled with a fan and I am done;-)
First on my list: Buy 4 cases of 24... half an hour later: Done... one hour later: Second on the list: Funny, I don't remember now...
When I put a beer in the freezer too long but not that long, when I take it out of the freezer, I can see it is pretty 100% liquid inside the bottle. Now, taking it out of the freezer makes it warmer and opening it even warmer due to air circulation inside the bottle.
Well, when I open it, it turns to ice so I make my beer freeze by making it warmer so nothing new here;--))))
Very seriously, I swear this is true but I understand it could be due to other factors that the ones described in TFA like pressure inside the bottle but I thought it would interesting to mention anyway.
Haven't anybody else seen their beer freeze in their hand while opening it just after it has been in the freezer although it was in a liquid state when they actually took it out of the freezer ?
Too bad if it is, we have been waiting for this for a while now since silicon based chips kind of reached their frequency limits. Of course, there is quantum computing but it is not coming to your local store soon;-))
It would be nice to be able to fit a 100 gigahertz chip in current hardware architectures...
Damn it, some hospital staff even posted a rotating picture of my own personal DNA on Wikipedia. What can I do about this ? Can I force them to remove it ?
Yeah you are right, I shouldn't have used that argument in the first place, it led to a misunderstanding that Java was using more resources;-((
I first understood your point although but re-thinking about it, I came to the conclusion that Java wasn't really requiring more resources as my statement led to believe. So, my statement was false. After a second thought at it, I tried to demonstrate that with the best examples I could think of. I wouldn't have replied to yourself "hating the argument" if I hadn't come to the conclusion that my argument led to a misunderstanding.
If it was true that Java needed more memory and that you hated the "get yourself a machine" argument, then there would have been nothing to reply to you.
So I understand your point and also, I ain't pretending my "ecosystem-is-better-than-yours", I am just sharing experiences I had with java and other solutions.;-)
To my defense, I am a victim of reading/. too much so I now realize that myself had started to believe that Java needs more memory than other solutions do;-)
Indeed, java's "references" is just a term to abstract pointers and java only uses references, it is not possible to pass a copy as an argument except for primitive types (8 primitive types and String isn't one of them). So, Java almost use pointers only !;-)))
While coding in C, I have always liked pointers. Understanding pointers is a "feature" that many Java developers lack. It sure helps a lot to understand pointers to get better at coding in Java.
Being a C developer that enjoyed pointers so much, I jumped in the Java band wagon early when I understood what the language was all about.
As a side note, note that the people who created Java were much more C developers than smalltalk developers for example.
The only real private data you have is the one you keep in your head or write on a piece of paper as long as nobody has access to the said piece of paper.
Don't get me wrong here, I still encourage privacy online defenders to continue their efforts but the above statement will always remain a fact when you think about it carefully. Electronic data goes with inherent risks for privacy in my humble opinion;-))
If you log in typing in a password, it might be easier for somebody to get your password by looking over your shoulder, installing a camera in your premises or use a keyboard sniffer. In the case of password authentication, every time you log in is a weak point.
On 512MB machines, I set Java to use 256MB or even 128MB....
A tomcat server with many applications deployed on it will run fine with 128MB reserved to it. It will run a little slower but so would PHP. PHP uses more OS level buffers/cache to run efficiently so it would also run slower on a 128MB machine due to the lack of buffers/cache memory. Java doesn't need as much buffers/cache to run efficiently because it uses its reserved memory to accomplish the same, usually more efficiently. Also, look at the size of a running apache process when compiled with mod_php compared to an apache server without it, 80MB for a single apache process and I use pre_fork so I have many of them !;-)
no php: nobody 2485 0.0 0.0 7392 2128 ? S 18:09 0:00/usr/local/apache/bin/httpd -k start
Before tomcat and application servers were created, I used to run my own custom jsp server on hosts that had 128MB of memory and these hosts were running many other servers (dns, apache, etc...)
I started to develop in Java on a 12MB 386 machine running Linux. Of course you would have to use vi to write code on a 12MB machine, eclipse wouldn't run on it but neither would Visual Studio I guess...
Can you please explain the specific problem that you are experiencing with regards to running java on low memory machines ?
> If java is backward compatible then why do bugfix releases keep breaking java apps?
Untrue, as I said, fully 100% pure java code apps are 100% backwards compatible.
The problems you are referring to are mostly caused by native C libraries used by the JVM that many implemented (Oracle, IBM, etc. to name a few) without regards for the advantages of writing pure Java Code.
Native C libraries used by the JVM should be viewed as "C extension to the JVM". Of course when you use them, you risk suffering the same problems as one would experience in C, your native C libraries are completely and entirely out of control of the JVM;-)))
VM, like the name suggests, use virtual memory, not necessarily RAM.
Typically a java VM needs 25% of the memory it uses to be resident (mapped to real RAM). When running into a VM (guest OS), that percentage may drop to 5 or 10% because the virtualization brings another layer of virtual memory that the programs think is real RAM.
On a 4 GB machine, I typically run 10 VM which all think they have 1 GB available to them. On the VM, each runs a java VM that is configured to use 512 MB of java memory, with OS overhead, the java VMs end up using around 800MB of memory (not necessarily real RAM).
Do the maths;-) I still do not think saying that "Java needs to much memory" is a valid point. The truth is that it doesn't matter how much memory you have available, an application in its Java version will handle more load than, for example, the same application in its PHP version without regards for the machine it is running on.
A lot of people freak out when they see how much memory a java VM reserves on startup without digging any deeper. If they did, they would find out that java is more efficient without regards for the hardware available.
Also, most people that understand what I am trying to explain have given up a long time ago trying to explain this on/.;-))))
All what you say is correct with one subtle nuance;
Java coding guidelines states to specifically close() things like files and sockets as soon as you are done with them so there is no risk of running out of file descriptors like you are suggesting when coding in Java if you follow the guideline. The "close()" call is mapped to the underlying OS call so the file descriptors are freed before garbage collection.
It's a well known fact that you should not rely on garbage collection to free resources like files or sockets although garbage collection usually takes care of closing the sockets.
Plain JDBC apps that rely on garbage collection to close a SQL connection only in one spot in the whole program can typically open 100 or 200 connections to the database before garbage collection runs and close them;-)))
By the way, files and sockets getting closed by garbage collection have a lot less to do with "how smart the garbage collector is" than it has to do with the programmer overwriting the finalize() method of its object in order to free resources used by the said object.
Again, one should never rely on garbage collection to close resources that maps to a OS resource like a file or a socket, but close() it explicitly when done with it but here is the finalize() method in java.io.FileInputStream() anyway;-)
protected void finalize() throws IOException {
387 if ((fd != null) && (fd != fd.in)) {
388
389/*
390 * Finalizer should not release the FileDescriptor if another
391 * stream is still using it. If the user directly invokes
392 * close() then the FileDescriptor is also released.
393 */
394 runningFinalize.set(Boolean.TRUE);
395 try {
396 close();
397 } finally {
398 runningFinalize.set(Boolean.FALSE);
399 }
400 }
401 }
OK, my OP was a joke intended at illustrating that it seems better to have something built-in the language specification than using one of the many third party libraries available to implement it or even worse, to go your own way...
I haven't coded any new functionality in C++ for many years, I only maintain C/C++ stuff now...
So, I am not really developing anything similar to what I mentioned in my OP....;-))
> It keeps track whether an object can be reached my the main program or not.
Not really the main program but more precisely a running Thread.
A running Thread might be unreachable from the main program which could potentially cause memory leaks as I have mentioned in another post.
To cause memory leaks in Java: Fork some Threads which use a bunch of objects and do not keep any reference to the Threads in the main program.
The correct way to do this is to keep references to the running Threads in the main program and to cause them to terminate when the main program wishes them to.
> Usually, this involves Swing and dialogs that were closed and forgotten about, and not properly dereferenced.
This is very new to me !!!
In Java, you do not "dereference" (e.g. myobject = null ). Read on how the garbage collector works. People recommending to do "myObject = null" usually do not know what they are talking about although I have seen it many times...
Here is an example:
if ( true) {
Object myObject = new Object(); }// myObject will be garbage collected here and the memory will be freed...
Application servers based on Java are heavy only on start up, the allocated memory is then reused which makes it light on system load once started.
Java uses some of its memory to cache machine code in order to re-execute it the next time it is needed and this also makes it light on system load.
Simply by using top, you could understand what I am talking about. Java uses more memory but it is otherwise very light on system load and guess what ?
Machines typically have 4 GB of ram nowadays.
Most people bitching about Java being heavy do not understand what I am trying to explain to you here;-)
> The main problem is compilation speed. C++ compilers are just plain slow.
Are you saying C++ doesn't have development platforms that compile your code in real time as you modify it ?
I haven't been coding in C++ for a while but I assumed something similar to eclipse was available for C++ developers. Heck, C++ must be supported by eclipse so doesn't it compile the code in real time as you modify it.
I am just curious, maybe it is harder to acheive this with C++,
This happens sometimes when I screw up doing pointer arithmetics or when I do not check array bounds.
To cure this, I started designing a system were I will abstract pointers with my own custom library. It will also automatically free the memory from unused objects. I will call it "memory recollection".
I am also designing my own custom third party library to automatically check array bounds;-))
I use bash scripts everywhere for "run once in a while" tasks but...
1) Bash scripts are usually heavy weight with regards to resources needed (creating many processes on the system. etc...).
> and the odds are very favorable that the damned thing will work.
2) Java is backward compatible since the very first version. For me, this tells something about the qualification of the people creating/maintaining ANY language or OS, etc.
Slashdot Mirror
> Web App Scanners Miss Half of Vulnerabilities
Well this is no surprise to me. Designing/testing secure systems is much more than scanning for vulnerabilities.
Scanning is only one of the tool to use to accomplish the goal.
Sure, I hinted about this in my post...
But you still just gave me a great idea: I will design a beer based air conditioner ( air cooler ) and sell it/publish it on sites similar to engadget ;-)))
Put in 4 cases of 24 and have some mechanism opening them one by one coupled with a fan and I am done ;-)
First on my list: Buy 4 cases of 24...
half an hour later:
Done...
one hour later:
Second on the list: Funny, I don't remember now...
When I put a beer in the freezer too long but not that long, when I take it out of the freezer, I can see it is pretty 100% liquid inside the bottle. Now, taking it out of the freezer makes it warmer and opening it even warmer due to air circulation inside the bottle.
Well, when I open it, it turns to ice so I make my beer freeze by making it warmer so nothing new here ;--))))
Very seriously, I swear this is true but I understand it could be due to other factors that the ones described in TFA like pressure inside the bottle but I thought it would interesting to mention anyway.
Haven't anybody else seen their beer freeze in their hand while opening it just after it has been in the freezer although it was in a liquid state when they actually took it out of the freezer ?
> Silicon has been "about to reach it's limits" since the late 90's.
Maybe a little later if we trust this graph, granted it has been forecasted for longer than that although :
http://smoothspan.files.wordpress.com/2007/09/clockspeeds.jpg?w=805
> Surely that is some sort of joke.
Too bad if it is, we have been waiting for this for a while now since silicon based chips kind of reached their frequency limits. Of course, there is quantum computing but it is not coming to your local store soon ;-))
It would be nice to be able to fit a 100 gigahertz chip in current hardware architectures...
Damn it, some hospital staff even posted a rotating picture of my own personal DNA on Wikipedia. What can I do about this ? Can I force them to remove it ?
http://en.wikipedia.org/wiki/File:ADN_animation.gif
Yeah you are right, I shouldn't have used that argument in the first place, it led to a misunderstanding that Java was using more resources ;-((
I first understood your point although but re-thinking about it, I came to the conclusion that Java wasn't really requiring more resources as my statement led to believe. So, my statement was false. After a second thought at it, I tried to demonstrate that with the best examples I could think of. I wouldn't have replied to yourself "hating the argument" if I hadn't come to the conclusion that my argument led to a misunderstanding.
If it was true that Java needed more memory and that you hated the "get yourself a machine" argument, then there would have been nothing to reply to you.
So I understand your point and also, I ain't pretending my "ecosystem-is-better-than-yours", I am just sharing experiences I had with java and other solutions. ;-)
To my defense, I am a victim of reading /. too much so I now realize that myself had started to believe that Java needs more memory than other solutions do ;-)
Cheers and sorry for the misunderstanding ;-))
Désolé de t'avoir fait marcher JF, je ne croyais pas que quiconque me prendrait au sérieux ;-))
http://slashdot.org/comments.pl?sid=1534682&cid=31031434
Indeed, java's "references" is just a term to abstract pointers and java only uses references, it is not possible to pass a copy as an argument except for primitive types (8 primitive types and String isn't one of them). So, Java almost use pointers only ! ;-)))
While coding in C, I have always liked pointers. Understanding pointers is a "feature" that many Java developers lack. It sure helps a lot to understand pointers to get better at coding in Java.
Being a C developer that enjoyed pointers so much, I jumped in the Java band wagon early when I understood what the language was all about.
As a side note, note that the people who created Java were much more C developers than smalltalk developers for example.
The only real private data you have is the one you keep in your head or write on a piece of paper as long as nobody has access to the said piece of paper.
Don't get me wrong here, I still encourage privacy online defenders to continue their efforts but the above statement will always remain a fact when you think about it carefully. Electronic data goes with inherent risks for privacy in my humble opinion ;-))
Hey, thanks a lot for enlightening me on the topic, I was kind of surprised nobody replied to me sooner after I posted ;-(
Thanks again ! ;-))
If you log in typing in a password, it might be easier for somebody to get your password by looking over your shoulder, installing a camera in your premises or use a keyboard sniffer. In the case of password authentication, every time you log in is a weak point.
No problems,
On 512MB machines, I set Java to use 256MB or even 128MB....
A tomcat server with many applications deployed on it will run fine with 128MB reserved to it. It will run a little slower but so would PHP. PHP uses more OS level buffers/cache to run efficiently so it would also run slower on a 128MB machine due to the lack of buffers/cache memory. Java doesn't need as much buffers/cache to run efficiently because it uses its reserved memory to accomplish the same, usually more efficiently. Also, look at the size of a running apache process when compiled with mod_php compared to an apache server without it, 80MB for a single apache process and I use pre_fork so I have many of them ! ;-)
no php: /usr/local/apache/bin/httpd -k start
nobody 2485 0.0 0.0 7392 2128 ? S 18:09 0:00
mod_php: /usr/sbin/httpd
nobody 3610 0.0 0.1 84348 6804 ? S Jan18 0:01
Before tomcat and application servers were created, I used to run my own custom jsp server on hosts that had 128MB of memory and these hosts were running many other servers (dns, apache, etc...)
I started to develop in Java on a 12MB 386 machine running Linux. Of course you would have to use vi to write code on a 12MB machine, eclipse wouldn't run on it but neither would Visual Studio I guess...
Can you please explain the specific problem that you are experiencing with regards to running java on low memory machines ?
> If java is backward compatible then why do bugfix releases keep breaking java apps?
Untrue, as I said, fully 100% pure java code apps are 100% backwards compatible.
The problems you are referring to are mostly caused by native C libraries used by the JVM that many implemented (Oracle, IBM, etc. to name a few) without regards for the advantages of writing pure Java Code.
Native C libraries used by the JVM should be viewed as "C extension to the JVM". Of course when you use them, you risk suffering the same problems as one would experience in C, your native C libraries are completely and entirely out of control of the JVM ;-)))
> Just a nitpick,
No problems ;-)
VM, like the name suggests, use virtual memory, not necessarily RAM.
Typically a java VM needs 25% of the memory it uses to be resident (mapped to real RAM). When running into a VM (guest OS), that percentage may drop to 5 or 10% because the virtualization brings another layer of virtual memory that the programs think is real RAM.
On a 4 GB machine, I typically run 10 VM which all think they have 1 GB available to them. On the VM, each runs a java VM that is configured to use 512 MB of java memory, with OS overhead, the java VMs end up using around 800MB of memory (not necessarily real RAM).
Do the maths ;-) I still do not think saying that "Java needs to much memory" is a valid point. The truth is that it doesn't matter how much memory you have available, an application in its Java version will handle more load than, for example, the same application in its PHP version without regards for the machine it is running on.
A lot of people freak out when they see how much memory a java VM reserves on startup without digging any deeper. If they did, they would find out that java is more efficient without regards for the hardware available.
Also, most people that understand what I am trying to explain have given up a long time ago trying to explain this on /. ;-))))
Cheers,
All what you say is correct with one subtle nuance;
Java coding guidelines states to specifically close() things like files and sockets as soon as you are done with them so there is no risk of running out of file descriptors like you are suggesting when coding in Java if you follow the guideline. The "close()" call is mapped to the underlying OS call so the file descriptors are freed before garbage collection.
It's a well known fact that you should not rely on garbage collection to free resources like files or sockets although garbage collection usually takes care of closing the sockets.
Plain JDBC apps that rely on garbage collection to close a SQL connection only in one spot in the whole program can typically open 100 or 200 connections to the database before garbage collection runs and close them ;-)))
By the way, files and sockets getting closed by garbage collection have a lot less to do with "how smart the garbage collector is" than it has to do with the programmer overwriting the finalize() method of its object in order to free resources used by the said object.
Again, one should never rely on garbage collection to close resources that maps to a OS resource like a file or a socket, but close() it explicitly when done with it but here is the finalize() method in java.io.FileInputStream() anyway ;-)
protected void finalize() throws IOException { /*
387 if ((fd != null) && (fd != fd.in)) {
388
389
390 * Finalizer should not release the FileDescriptor if another
391 * stream is still using it. If the user directly invokes
392 * close() then the FileDescriptor is also released.
393 */
394 runningFinalize.set(Boolean.TRUE);
395 try {
396 close();
397 } finally {
398 runningFinalize.set(Boolean.FALSE);
399 }
400 }
401 }
OK, my OP was a joke intended at illustrating that it seems better to have something built-in the language specification than using one of the many third party libraries available to implement it or even worse, to go your own way...
I haven't coded any new functionality in C++ for many years, I only maintain C/C++ stuff now...
So, I am not really developing anything similar to what I mentioned in my OP.... ;-))
> It keeps track whether an object can be reached my the main program or not.
Not really the main program but more precisely a running Thread.
A running Thread might be unreachable from the main program which could potentially cause memory leaks as I have mentioned in another post.
To cause memory leaks in Java: Fork some Threads which use a bunch of objects and do not keep any reference to the Threads in the main program.
The correct way to do this is to keep references to the running Threads in the main program and to cause them to terminate when the main program wishes them to.
Nope, just like in Java where it is built-in the language specifications ;-)))
> Usually, this involves Swing and dialogs that were closed and forgotten about, and not properly dereferenced.
This is very new to me !!!
In Java, you do not "dereference" (e.g. myobject = null ). Read on how the garbage collector works. People recommending to do "myObject = null" usually do not know what they are talking about although I have seen it many times...
Here is an example:
if ( true) { // myObject will be garbage collected here and the memory will be freed...
Object myObject = new Object();
}
code continues...
Application servers based on Java are heavy only on start up, the allocated memory is then reused which makes it light on system load once started.
Java uses some of its memory to cache machine code in order to re-execute it the next time it is needed and this also makes it light on system load.
Simply by using top, you could understand what I am talking about. Java uses more memory but it is otherwise very light on system load and guess what ?
Machines typically have 4 GB of ram nowadays.
Most people bitching about Java being heavy do not understand what I am trying to explain to you here ;-)
> The main problem is compilation speed. C++ compilers are just plain slow.
Are you saying C++ doesn't have development platforms that compile your code in real time as you modify it ?
I haven't been coding in C++ for a while but I assumed something similar to eclipse was available for C++ developers. Heck, C++ must be supported by eclipse so doesn't it compile the code in real time as you modify it.
I am just curious, maybe it is harder to acheive this with C++,
Thanks for answers everybody. ;-)
> An experienced C++ programmer rarely creates memory leaks,
An INEXPERIENCED java programmer NEVER creates memory leaks,
An experienced java programmer could manage to create memory leaks using threads but you almost have to do this on purpose ;-))
This happens sometimes when I screw up doing pointer arithmetics or when I do not check array bounds.
To cure this, I started designing a system were I will abstract pointers with my own custom library. It will also automatically free the memory from unused objects. I will call it "memory recollection".
I am also designing my own custom third party library to automatically check array bounds ;-))
> or any you list, it's light weight,
I use bash scripts everywhere for "run once in a while" tasks but...
1) Bash scripts are usually heavy weight with regards to resources needed (creating many processes on the system. etc...).
> and the odds are very favorable that the damned thing will work.
2) Java is backward compatible since the very first version. For me, this tells something about the qualification of the people creating/maintaining ANY language or OS, etc.