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  • Is Apple getting out of the general purpose development platform business?

    - by Charles E. Grant
    I've been doing general ANSI C/Console C++/Java/Web development on Mac hardware for about ten years. I make no claims of objective superiority over other platforms, it just satisfies my personal tastes. With the success of the iPhone and the related App store there was some speculation that Apple would get out of the general purpose computer market, and become a closed software ecosystem, focusing on consumer appliances. I pooh-poohed the speculation at the time, but this week Apple announced that a) they were opening an App store for the Mac, b) Java applications would not be eligible for the App store, c) the Apple JVM was being deprecated and might not be available for future releases of OS X. I'm not a Java developer per se, but I work in a research lab that occasionally writes Java applications, and also depends on tools written Java. This has the potential to be a huge pain in the butt for us. As of now, there is no other JVM for OS X that we can point our end users to. Soy Latte and OpenJDK might be appropriate for developers, but the complexity of the installation makes them inappropriate for end users. Eventually I expect Oracle/SUN will produce a replacement JVM for OS X. More worrisome to me is that Apple used to specifically advertise that it was an excellent platform for scientific development, because they supported all major language platforms. Is the deprecation of their JVM a sign that this market no longer interests them?

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  • JVM memory initializazion error after windows update

    - by gianni
    We have three Windows Server 2003 with 2 GB RAM. Server1 tomcat 5.5.25 jvm version SUN 1.6.0_11-b03 Server2 tomcat 5.5.25 jvm version SUN 1.6.0_14-b08 Server3 tomcat 6.0.18 jvm version SUN 1.6.0_14-b08 For the three servers JVM parameters are: -XX:MaxPermSize=256m -Dcatalina.base=C:\Programmi\Apache Group\apache-tomcat-5.5.25 -Dcatalina.home=C:\Programmi\Apache Group\apache-tomcat-5.5.25 -Djava.endorsed.dirs=C:\Programmi\Apache Group\apache-tomcat-5.5.25\common\endorsed -Djava.io.tmpdir=C:\Programmi\Apache Group\apache-tomcat-5.5.25\temp vfprintf -Xms512m -Xmx1024m For some months everithing worked fine. Last friday we installed some windows updates. After the reboot tomcat doesnt start with error: Error occurred during initialization of VM Could not reserve enough space for object heap We reduced the parameter -Xmx1024m to -Xmx768m and now tomcat starts. But we need greater max heap size What happened to our servers ? Thanks in advance.

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  • C# 4.0: Alternative To Optional Arguments

    - by Paulo Morgado
    Like I mentioned in my last post, exposing publicly methods with optional arguments is a bad practice (that’s why C# has resisted to having it, until now). You might argument that your method or constructor has to many variants and having ten or more overloads is a maintenance nightmare, and you’re right. But the solution has been there for ages: have an arguments class. The arguments class pattern is used in the .NET Framework is used by several classes, like XmlReader and XmlWriter that use such pattern in their Create methods, since version 2.0: XmlReaderSettings settings = new XmlReaderSettings(); settings.ValidationType = ValidationType.Auto; XmlReader.Create("file.xml", settings); With this pattern, you don’t have to maintain a long list of overloads and any default values for properties of XmlReaderSettings (or XmlWriterSettings for XmlWriter.Create) can be changed or new properties added in future implementations that won’t break existing compiled code. You might now argue that it’s too much code to write, but, with object initializers added in C# 3.0, the same code can be written like this: XmlReader.Create("file.xml", new XmlReaderSettings { ValidationType = ValidationType.Auto }); Looks almost like named and optional arguments, doesn’t it? And, who knows, in a future version of C#, it might even look like this: XmlReader.Create("file.xml", new { ValidationType = ValidationType.Auto });

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  • How can I process command line arguments in Python?

    - by photographer
    What would be an easy expression to process command line arguments if I'm expecting anything like 001 or 999 (let's limit expectations to 001...999 range for this time), and few other arguments passed, and would like to ignore any unexpected? I understand if for example I need to find out if "debug" was passed among parameters it'll be something like that: if 'debug' in argv[1:]: print 'Will be running in debug mode.' How to find out if 009 or 575 was passed? All those are expected calls: python script.py python script.py 011 python script.py 256 debug python script.py 391 xls python script.py 999 debug pdf At this point I don't care about calls like that: python script.py 001 002 245 568 python script.py some unexpected argument python script.py 0001 python script.py 02 ...first one - because of more than one "numeric" argument; second - because of... well, unexpected arguments; third and fourth - because of non-3-digits arguments.

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  • Book (or resource) on Java bytecode

    - by Andrea
    I am looking for some resources on the JVM bytecode. Ideally I would for a short book; something more than a blog post but not a 800 pages tome. If it is relevant, I am a Scala developer, not a Java one, although I know Java just fine. I would like something that allowed me to read JVM bytecode and answer questions such as: Why does the bytecode has to know about high level construct such as classes? Are subtyping relations still visible in bytecode? How does type erasure work exactly? How do Oracle and Dalvik bytecode differ, and what consequences does this have for, say, developing Android apps with Scala? How does the JVM manage the stack, and why exactly this creates issues with tail call elimination? and so on.

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  • JVM Language Summit 2012 - Registration Open

    - by arungupta
    The 2012 edition of the JVM Languages Summit is Jul 30 - Aug 1, at Oracle's Santa Clara Campus. This is an "an open technical collaboration among language designers, compiler writers, tool builders, runtime engineers, and VM architects". There are presentations, workshops, and lightning talks. About 70 language and VM implementers attended last year and the talks were recorded. Some videos from last year are available here. Check out the Main Page, the Agenda, Logistics, and the Wiki. See the Registration Online; for questions, send mail to inquire AT jvmlangsummit.com.

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  • Named arguments (parameters) as a readability aid

    - by Damian Mehers
    A long time ago I programmed a lot in ADA, and it was normal to name arguments when invoking a function - SomeObject.DoSomething(SomeParameterName = someValue); Now that C# supports named arguments, I'm thinking about reverting to this habit in situations where it might not be obvious what an argument means. You might argue that it should always be obvious what an argument means, but if you have a boolean argument, and callers are passing in "true" or "false" then qualifying the value with the name makes the call site more readable. contentFetcher.DownloadNote(note, manual : true); I guess I could create Enums instead of using true or false (Manual, Automatic in this case). What do you think about occasionally using named arguments to make code easier to read?

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  • Input to program without command-line arguments

    - by Core Xii
    Let's assume that there are no command-line arguments. How do you pass input data to a program? I'm thinking you'd write the input to a file with a specific name, such that the program knows to open and read it as input. However, how would one discover the name of that file? Usually, running a command-line program without arguments or with some standard help argument (e.g. \?) produces some instruction on how to use it. But given an environment with no command-line arguments, how does one discover how to operate a program?

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  • Java Spotlight Episode 35: JVM Performance and Quality

    - by Roger Brinkley
    Tweet Interview with Vladimir Ivanov, Ivan Krylov, Sergey Kuksenko on the JDK 7 Java Virtual Machine performance and quality. Joining us this week on the Java All Star Developer Panel are Dalibor Topic, Java Free and Open Source Software Ambassador, and Alexis Moussine-Pouchkine, Java EE Developer Advocate. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link: Java Spotlight Podcast in iTunes. Show Notes News Java 7 Launch Event GlassFish 3.1.1 re-planning done, first RC on July 7th, lots of component updates following customer and community feedback Mojarra 2.1.2 is here, just a little ahead of the GlassFish 3.1.1 release. In other JSF-related news, JSF 2.0 has a first expert draft New OpenJDK Project proposed: JDK 7 Update Events June 20-23 JAX, San Jose, CA June 21 Java + MySQL Webinar at 9:00 AM PDT June 21-23 JaZoon, Zurich, Switzerland June 22nd and 28th GlassFish Webinars (one in Portuguese) June 29-July 2 12th Forum Internatioal Software Livre, Porto Alegre, Brazil July 3, Sao Jose do Rio Preto, Brazil July 5, Brasilia, Brazil (DFJUG) July 6, Goiania, Brazil (GOJava) July 6-10 The Developers Conference, Sao Paulo, Brazil July 7 Java 7 Launch Event live in Redwood Shores, CA; Sao Paulo, BR; London, England. July 9, Joao Pessoa, Brazil (PBJUG) July 11, Natal, Brazil (JavaRN) July 14, Fortaleza, Brazil (CEJUG) July 16, Salvador, Brazil (JavaBahia) July 19, Toledo, Brazil (UNIPAR) July 21, Maringa, Brazil (RedFoot) Feature interview This weeks feature interview is with Vladimir Ivanov, HotSpot JVM Quality Engingeer;  Ivan Krylov, Licensee Engineering;  and Sergey Kuksenko, Java SE Performance Team on the JDK 7 Java Virtual Machine peformance and quality. What's Cool Ongoing OpenJDK Bylaws ratification results Show Transcripts Transcript for this show is available here when available

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  • Inverted schedctl usage in the JVM

    - by Dave
    The schedctl facility in Solaris allows a thread to request that the kernel defer involuntary preemption for a brief period. The mechanism is strictly advisory - the kernel can opt to ignore the request. Schedctl is typically used to bracket lock critical sections. That, in turn, can avoid convoying -- threads piling up on a critical section behind a preempted lock-holder -- and other lock-related performance pathologies. If you're interested see the man pages for schedctl_start() and schedctl_stop() and the schedctl.h include file. The implementation is very efficient. schedctl_start(), which asks that preemption be deferred, simply stores into a thread-specific structure -- the schedctl block -- that the kernel maps into user-space. Similarly, schedctl_stop() clears the flag set by schedctl_stop() and then checks a "preemption pending" flag in the block. Normally, this will be false, but if set schedctl_stop() will yield to politely grant the CPU to other threads. Note that you can't abuse this facility for long-term preemption avoidance as the deferral is brief. If your thread exceeds the grace period the kernel will preempt it and transiently degrade its effective scheduling priority. Further reading : US05937187 and various papers by Andy Tucker. We'll now switch topics to the implementation of the "synchronized" locking construct in the HotSpot JVM. If a lock is contended then on multiprocessor systems we'll spin briefly to try to avoid context switching. Context switching is wasted work and inflicts various cache and TLB penalties on the threads involved. If context switching were "free" then we'd never spin to avoid switching, but that's not the case. We use an adaptive spin-then-park strategy. One potentially undesirable outcome is that we can be preempted while spinning. When our spinning thread is finally rescheduled the lock may or may not be available. If not, we'll spin and then potentially park (block) again, thus suffering a 2nd context switch. Recall that the reason we spin is to avoid context switching. To avoid this scenario I've found it useful to enable schedctl to request deferral while spinning. But while spinning I've arranged for the code to periodically check or poll the "preemption pending" flag. If that's found set we simply abandon our spinning attempt and park immediately. This avoids the double context-switch scenario above. One annoyance is that the schedctl blocks for the threads in a given process are tightly packed on special pages mapped from kernel space into user-land. As such, writes to the schedctl blocks can cause false sharing on other adjacent blocks. Hopefully the kernel folks will make changes to avoid this by padding and aligning the blocks to ensure that one cache line underlies at most one schedctl block at any one time.

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  • What could be the Java successor Oracle wants to invest in?

    - by deamon
    I've read that Oracle wants to invest into another language than Java: "On the other hand, Oracle has been particularly supportive of alternative JVM languages. Adam Messinger ( http://www.linkedin.com/in/adammessinger ) was pretty blunt at the JVM Languages Summit this year about Java the language reaching it's logical end and how Oracle is looking for a 'higher level' language to 'put significant investment into.'" But what language could be the one Oracle wants to invest in? Is there another candidate than Scala?

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  • Java Terms that are Plagued with Vaguery

    - by Adam Tannon
    What's the difference between a Java Process (what your OS sees) and a JVM? Are they one in the same or are they actually different? How are the JRE and JDK different (in purpose and file content), and which one contains the libraries for Java SE? What's the difference between the Java "Runtime" and a JVM? These are questions I've been asking myself (and colleagues) for years and everybody seems to have very different answers.

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  • Java heap space

    - by java_mouse
    In Java/JVM, why do we call the memory place where Java creates objects as "Heap"? Does it use the Heap Data Structure to create/remove/maintain the objects? As I read in the documentation of Heap data structure, the algorithm compares the objects with existing nodes and places them in such a way that Parent object is "greater" than the children. ( Or "lesser" in case of min heap). So in JVM, how are the objects compared against each other before placing them in the heap?

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  • Why is the JVM stack-based and the DalvikVM register based?

    - by aioobe
    I'm curious, why did Sun decide to make the JVM stack-based and Google decide to make the DalvikVM register based? I suppose the JVM can't really assume that a certain number of registers are available on the target platform, since it is supposed to be platform independent. Therefor it just postpones the register-allocation etc, to the JIT compiler. (Correct me if I'm wrong.) So the Android guys thought, "hey, that's inefficient, let's go for a register based vm right away..."? But wait, there are multiple different android devices, what number of registers did the Dalvik target? Are the Dalvik opcodes hardcoded for a certain number of registers? Do all current Android devices on the market have about the same number of registers? Or, is there a register re-allocation performed during dex-loading? How does all this fit together?

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  • Is there a way to tell JVM to optimize my code before processing?

    - by Rogach
    I have a method, which takes much time to execute first time. But after several invocations, it takes about 30 times less time. So, to make my application respond to user interaction faster, I "warm-up" this method (5 times) with some sample data on initialization of application. But this increases app start-up time. I read, that JVM's can optimize and compile my java code to native, thus speeding things up. I wanted to know - maybe there is some way to explicitly tell JVM that I want this method to be compiled on startup of application?

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  • JVM specification and Java compiler code useful for SCJP preparation ?

    - by BenoitParis
    I'm preparing the SCJP exam with the almost official study book ("SCJP Sun Certified Programmer for Java 6 Exam 310-065") I understand that Java programming is writting code that fulfills a certain high-level contract; So that Java can stay platform-independent. However, I have trouble understanding and remembering things when it comes to highly specific SCJP items (and they are numerous) The book stays high-level and does not provide examples of how one compiler would handle things. This is the same thing for runtime issues (JVM level): things are too much abstract for me. Rules often seems arbitrary and therefore, with no well defined purpose, are difficult to remember. Or maybe it's that sometimes I just don't get the underlying purpose. And here is the question: Would a JVM specification and/or some java compiler code help in preparing the SCJP? Have you had the need for such material or is the book sufficient enough? Also, please share the resources you used, apart from the book.

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  • Can I replicate some of the optimisations done by the JVM by hand?

    - by Subb
    I'm working on a Sudoku solver at school and we're having a little performance contest. Right now, my algorithm is pretty fast on the first run (about 2.5ms), but even faster when I solve the same puzzle 10 000 times (about 0.5ms for each run). Those timing are, of course, depend of the puzzle being solved. I know the JVM do some optimization when a method is called multiple time, and this is what I suspect is happening. I don't think I can further optimize the algorithm itself (though I'll keep looking), so I was wondering if I could replicate some of the optimizations done by the JVM. Note : compiling to native code is not an option Thanks!

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  • ???????·?????????????????·??????·???????????WebLogic?????

    - by ???01
    Java EE??????????·????????????????????????????·??????·??????????????WebLogic Server???????????????????????????????????????·???????????????????????????????????·???????????????????????????????????????WebLogic Server????????? ????????????????????????2??????????(???)? ????????·?????????????????????????????? ???????????IT?????????????????/?????????????????????????????/??????????IT??????????????????????????????·??????????????????? ????????/???????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·?????????????????????????????? ?????????????????????????????????Oracle WebLogic Server???????????????????Java EE????????Java EE?????????????????????????????????????·??????·????????????????????????????????????????????????????????????????Java EE??????·???????????????????WebLogic Server?????Oracle Tuxedo???Oracle Coherence??????????????????????????????????????????·???????????????????????? ???????WebLogic Server???????????????????????????????????? ????????·?????????????????????????????????????(??·??????)??????????????????????????? ???·??????????????????????????? ???·????????????????????·????????WebLogic Server???????????1????????????????????????????????????????WebLogic Server???????????????????????????????????????? ???????????????2????????1???????????????????????????????????1?????????????????????????????? ???????????????????·???????????????? WebLogic Server??????????·?????????Java?????(JVM:Java Virtual Machine)????????????????????????????????????????????????????·???????????????????????????????????WebLogic Server??????????JVM????·??????????·??????(GC)???????????????????????????????? ?????????????????????????????????????·??????????????????????WebLogic Server????????1????????????????·?????????Web???????????????????????HTTP?????????????????????????????????????????????????????·????????????????????????????????????????????????????????????????????????????????? ???WebLogic Server?????????????????????????·?????????????????Web???????????URL?????????????????????????????HTTP??????????????WebLogic Server?????????????????????????????????????HTTP?????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????????????????????????????????????????????????????????????????Web?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·????????????????·??????????????????????????????????????????????????????????????????????????? ???????????????? ???????????????????????/?????????????????????????????????????? ???????1??????·??????????????????????·??????????????Java???????????????·?????????????????????????????????????????????????????????????????????????·?????????????????????????????????????????·??????????????????????1???????? WebLogic Server?????????·????????????????????????????????????????????????????????????????????????(??)??????????????????????????????·????????????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????WebLogic Server???????????????????????????????????????????????????? ???????·?????????JVM??????????????????????????????????WebLogic Server????JVM?JRockit???????????????????????????????????????·???????????????????????GC??????????????????????????????????????????????????????????????????????? ????????????????????? ?????·??????·???????????????????WebLogic Server???????????????????????????????????·??????????????????SpecjEnterprise2010??????????????????????? WebLogic Server?????????????????JVM?JRockit????????????????????????????JVM?????????????SPECjbb2005??????????????????????JRockit???????????? ???JVM???????????Java???????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit??????????????????·????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit?????????????????????????????????????????????????????? JRockit????????????????????????????????????????????JIT(Just In-Time)?????????????????????????????·?????????????????? ??????????????????????GC??????????????????????????????GC?????????JRockit?????????????????????????GC????????????????????????????????????????GC????????????????????????????????????GC?????????????????????????1?????????JRockit?GC???????????????????????????????????????????? ?????JRockit????Sun JVM????????JVM?????????????????????????Sun JVM?????????·??????????????????????????????????????????????????????JIT?????????????????????????·????????????????????????·?????????????????????????????????JVM???????1????? ???JVM Oracle JRockit??? ???? ···???JVM?Oracle JRockit??????????????????????????JRockit Flight Recorder????????????????? ?????45???????????????????????????????????? ?WMV?? ?MP4?? ?????????·???????????????????????????????·???/JVM????????????????????????????????WebLogic Server????????????????????????????????????????????????????????????????·??????·????????????WebLogic Server??????????????????????????????????????????????????????????????????????????????????

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  • ???????·?????????????????·??????·???????????WebLogic?????|WebLogic Channel|??????

    - by ???02
    Java EE??????????·????????????????????????????·??????·??????????????WebLogic Server???????????????????????????????????????·???????????????????????????????????·???????????????????????????????????????WebLogic Server????????? ????????????????????????2??????????(???)?????????·?????????????????????????????????????????IT?????????????????/?????????????????????????????/??????????IT??????????????????????????????·??????????????????? ????????/???????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·?????????????????????????????? ?????????????????????????????????Oracle WebLogic Server???????????????????Java EE????????Java EE?????????????????????????????????????·??????·????????????????????????????????????????????????????????????????Java EE??????·???????????????????WebLogic Server?????Oracle Tuxedo???Oracle Coherence??????????????????????????????????????????·???????????????????????????????WebLogic Server???????????????????????????????????? ????????·?????????????????????????????????????(??·??????)??????????????????????????????·???????――?????????????????????·????????????????????·????????WebLogic Server???????????1????????????????????????????????????????WebLogic Server???????????????????????????????????????? ???????????????2????????1???????????????????????????????????1?????????????????????????????????????????????????·????????????????WebLogic Server??????????·?????????Java?????(JVM:Java Virtual Machine)????????????????????????????????????????????????????·???????????????????????????????????WebLogic Server??????????JVM????·??????????·??????(GC)?????????????????????????????????????????????????????????????????????·??????????????????????WebLogic Server????????1????????????????·?????????Web???????????????????????HTTP?????????????????????????????????????????????????????·????????????????????????????????????????????????????????????????????????????????? ???WebLogic Server?????????????????????????·?????????????????Web???????????URL?????????????????????????????HTTP??????????????WebLogic Server?????????????????????????????????????HTTP???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????Web?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????·????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????/?????????????????????????????????????? ???????1??????·??????????????????????·??????????????Java???????????????·?????????????????????????????????????????????????????????????????????????·?????????????????????????????????????????·??????????????????????1???????? WebLogic Server?????????·????????????????????????????????????????????????????????????????????????(??)??????????????????????????????·????????????????????????????·??????????????????????????????????????????????????????????????????????????????????????????????????????WebLogic Server???????????????????????????????????????????????????????????·?????????JVM??????????????????????????????????WebLogic Server????JVM?JRockit???????????????????????????????????????·???????????????????????GC?????????????????????????????????????????????????????????????????????????????????????????????????·??????·???????????????????WebLogic Server???????????????????????????????????·??????????????????SpecjEnterprise2010???????????????????????WebLogic Server?????????????????JVM?JRockit????????????????????????????JVM?????????????SPECjbb2005??????????????????????JRockit???????????????JVM???????????Java???????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit??????????????????·????·??????????????????????????????????????????????????????????????????????????????????????????????????????????????????JRockit?????????????????????????????????????????????????????? JRockit????????????????????????????????????????????????JIT(Just In-Time)?????????????????????????????·?????????????????? ??????????????????????GC??????????????????????????????GC?????????JRockit?????????????????????????GC????????????????????????????????????????GC????????????????????????????????????GC?????????????????????????1?????????JRockit?GC?????????????????????????????????????????????????JRockit????Sun JVM????????JVM?????????????????????????Sun JVM?????????·??????????????????????????????????????????????????????JIT?????????????????????????·????????????????????????·?????????????????????????????????JVM???????1????????JVM Oracle JRockit??? ???? ···???JVM?Oracle JRockit??????????????????????????JRockit Flight Recorder????????????????? ?????45???????????????????????????????????? ?WMV?? ?MP4???????????·???????????????????????????????·???/JVM????????????????????????????????WebLogic Server????????????????????????????????????????????????????????????????·??????·????????????WebLogic Server??????????????????????????????????????????????????????????????????????????????????

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  • C++0x, How do I expand a tuple into variadic template function arguments?

    - by Gustaf
    Consider the case of a templated function with variadic template arguments: template<typename Tret, typename... T> Tret func(const T&... t); Now, I have a tuple t of values. How do I call func() using the tuple values as arguments? I've read about the bind() function object, with call() function, and also the apply() function in different some now-obsolete documents. The GNU GCC 4.4 implementation seems to have a call() function in the bind() class, but there is very little documentation on the subject. Some people suggest hand-written recursive hacks, but the true value of variadic template arguments is to be able to use them in cases like above. Does anyone have a solution to is, or hint on where to read about it?

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  • Is this error caused by a 64-bit library being accessed by a Java program running in a 32-bit JVM?

    - by Mike
    I'm trying to create a simple Java app that uses JNI to call some native functions. I've followed the examples in the JNI Programming Guide and can't seem to get them to work. I have the following Hello World program, written in Java: class HelloWorld { private native void print(); public static void main(String [] args) { new HelloWorld().print(); } static { System.load("/home/mike/Desktop/libHelloWorld.so"); } } I compile it using javac HelloWorld.java, just like normal. Then I run javah -jni HelloWorld, and finally the following: gcc34 -shared -fpic -o libHelloWorld.so -I/<path to JDK>/include -I/<path to JDK>/include/linux HelloWorld.c gcc34 is the name of the GCC program on my machine here at work (I don't control that) and I obviously place the real path to the JDK in that command. When I run my program, using the standard java HelloWorld, I get an error saying the following: Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/mike/Desktop/libHelloWorld.so: /home/mike/Desktop/libHelloWorld.so: wrong ELF class: ELFCLASS64 (Possible causes: architecture word width mismatch) at java.lang.ClassLoader$NativeLibrary.load(Native Method) at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1778) at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1674) at java.lang.Runtime.load0(Runtime.java:770) at java.lang.System.load(System.java:1003) at HelloWorld.<clinit>(HelloWorld.java:8) Could not find the main class: HelloWorld. Program will exit. I know I'm running a 32-bit JVM (and unfortunately, as of right now, I'm not allowed to get a 64-bit JVM). I tried telling GCC to compile in 32-bit mode using the "-m32" option, but we don't have (and again, can't get) what we need for that. Does this sound like a 32/64-bit conflict or something else?

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  • 32-bit JVM on 64-bit Windows crashes on launch with -Xmx1300m and plenty of free memory

    - by Konrad Garus
    I'm struggling with Java heap space settings. The default Java on Windows is the 32-bit client regardless of OS version (that's what Oracle recommends to all users). It appears to set max heap size to 256 MB by default, and that is too little for me. I use a custom launcher to start the application. I would like it to use more memory on computers with plenty RAM, and default to -Xmx512m on those with less RAM. As far as I'm aware, the only way is the static -Xmx setting (that has to be set on launch). I have a user who has 8 GB RAM, 64-bit Windows and 32-bit Java 7. Maximum memory visible to the JVM is 4G (as returned by querying OperatingSystemMXBean). I understand why, no issue. For some reason my application is unable to start for this user with -Xmx1300m, even though he has 2.3G free memory. He closed some applications (having 5G free memory), and still it would not launch. The error reported to me was: error occured during init of vm could not reserve enough space for object heap What's going on? Could it be that the 32-bit JVM is only able to address the "first" 4G of memory and has to have a 1300M block available within those first 4 gigabytes? How can I solve this problem, except for asking everyone to install 64-bit Java (what is unlikely to be acceptable)?

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  • grep - what arguments do you usually specify?

    - by meder
    My most common grep line is just.. grep -IRl "text" * However I'm kinda getting tired of retyping this over and over - is there some way I can make an alias command so that those arguments are always enabled? And, I was wondering what arguments you usually specify for text searching - my two arguments 'R' for recursion, 'I' for not including binary types like jpg/gif, and 'l' for line number seem a bit too minimal. Which arguments do you use?

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