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• How do people know so much about programming?

  - by Luciano

  I see people in this forums with a lot of points, so I assume they know about a lot of different programming stuff. When I was young I knew about basic (commodore) and the turbo pascal (pc). Then in college I learnt about C, memory management, x86 set, loop invariants, graphs, db query optimization, oop, functional, lambda calculus, prolog, concurrency, polymorphism, newton method, simplex, backtracking, dynamic programming, heuristics, np completeness, LR, LALR, neural networks, static & dynamic typing, turing, godel, and more in between. Then in industry I started with Java several years ago and learnt about it, and its variety of frameworks, and also design patterns, architecture patterns, web development, server development, mobile development, tdd, bdd, uml, use cases, bug trackers, process management, people management if you are a tech lead, profiling, security concerns, etc. I started to forget what I learnt in college... And then there is the stuff I don't know yet, like python, .net, perl, JVM stuff like groovy or scala.. Of course Google is a must for rapid documentation access to know if a problem has been solved already and how, and to keep informed about new stuff by blogs and places like this one. It's just too much or I just have a bad memory.. how do you guys manage it?

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• Infinite loop in regex in java

  - by carpediem

  Hello, My purpose is to match this kind of different urls: url.com my.url.com my.extended.url.com a.super.extended.url.com and so on... So, I decided to build the regex to have a letter or a number at start and end of the url, and to have a infinite number of "subdomains" with alphanumeric characters and a dot. For example, in "my.extended.url.com", "m" from "my" is the first class of the regex, "m" from "com" is the last class of the regex, and "y.", "extended." and "url." are the second class of the regex. Using the pattern and subject in the code below, I want the find method to return me a false because this url must not match, but it uses 100% of CPU and seems to stay in an infinite loop. String subject = "www.association-belgo-palestinienne-be"; Pattern pattern = Pattern.compile("^[A-Za-z0-9]\\.?([A-Za-z0-9_-]+\\.?)*[A-Za-z0-9]\\.[A-Za-z]{2,6}"); Matcher m = pattern.matcher(subject); System.out.println(" Start"); boolean hasFind = m.find(); System.out.println(" Finish : " + hasFind); Which only prints: Start I can't reproduce the problem using regex testers. Is it normal ? Is the problem coming from my regex ? Could it be due to my Java version (1.6.0_22-b04 / JVM 64 bit 17.1-b03) ? Thanks in advance for helping.

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• Memory leak of java.lang.ref.WeakReference objects inside JDK classes

  - by mandye

  The following simple code reproduces the growth of java.lang.ref.WeakReference objects in the heap: public static void main(String[] args) throws Exception { while (true) { java.util.logging.Logger.getAnonymousLogger(); Thread.sleep(1); } } Here is the output of jmap command within a few seconds interval: user@t1007:~ jmap -d64 -histo:live 29201|grep WeakReference 8: 22493 1079664 java.lang.ref.WeakReference 31: 1 32144 [Ljava.lang.ref.WeakReference; 106: 17 952 com.sun.jmx.mbeanserver.WeakIdentityHashMap$IdentityWeakReference user@t1007:~ jmap -d64 -histo:live 29201|grep WeakReference 8: 23191 1113168 java.lang.ref.WeakReference 31: 1 32144 [Ljava.lang.ref.WeakReference; 103: 17 952 com.sun.jmx.mbeanserver.WeakIdentityHashMap$IdentityWeakReference user@t1007:~ jmap -d64 -histo:live 29201|grep WeakReference 8: 23804 1142592 java.lang.ref.WeakReference 31: 1 32144 [Ljava.lang.ref.WeakReference; 103: 17 952 com.sun.jmx.mbeanserver.WeakIdentityHashMap$IdentityWeakReference Note that jmap command forces FullGC. JVM settings: export JVM_OPT="\ -d64 \ -Xms200m -Xmx200m \ -XX:MaxNewSize=64m \ -XX:NewSize=64m \ -XX:+UseParNewGC \ -XX:+UseConcMarkSweepGC \ -XX:MaxTenuringThreshold=10 \ -XX:SurvivorRatio=2 \ -XX:CMSInitiatingOccupancyFraction=60 \ -XX:+UseCMSInitiatingOccupancyOnly \ -XX:+CMSParallelRemarkEnabled \ -XX:+DisableExplicitGC \ -XX:+CMSClassUnloadingEnabled \ -XX:+PrintGCTimeStamps \ -XX:+PrintGCDetails \ -XX:+PrintTenuringDistribution \ -XX:+PrintGCApplicationConcurrentTime \ -XX:+PrintGCApplicationStoppedTime \ -XX:+PrintGCApplicationStoppedTime \ -XX:+PrintClassHistogram \ -XX:+ParallelRefProcEnabled \ -XX:SoftRefLRUPolicyMSPerMB=1 \ -verbose:gc \ -Xloggc:$GCLOGFILE" java version "1.6.0_18" Java(TM) SE Runtime Environment (build 1.6.0_18-b07) Java HotSpot(TM) Server VM (build 16.0-b13, mixed mode) Solaris 10/Sun Fire(TM) T1000

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• Executing bat file and returning the prompt

  - by Lieven Cardoen

  I have a problem with cruisecontrol where an ant scripts executes a bat file that doesn't give me the prompt back. As a result, the project in cruisecontrol keeps on bulding forever until I restart cruisecontrol. How can I resolve this? It's a startup.bat from wowza (Streaming Server) that I'm executing: @echo off call setenv.bat if not %WMSENVOK% == "true" goto end set _WINDOWNAME="Wowza Media Server 2" set _EXESERVER= if "%1"=="newwindow" ( set _EXESERVER=start %_WINDOWNAME% shift ) set CLASSPATH="%WMSAPP_HOME%\bin\wms-bootstrap.jar" rem cacls jmxremote.password /P username:R rem cacls jmxremote.access /P username:R rem NOTE: Here you can configure the JVM's built in JMX interface. rem See the "Server Management Console and Monitoring" chapter rem of the "User's Guide" for more information on how to configure the rem remote JMX interface in the [install-dir]/conf/Server.xml file. set JMXOPTIONS=-Dcom.sun.management.jmxremote=true rem set JMXOPTIONS=%JMXOPTIONS% -Djava.rmi.server.hostname=192.168.1.7 rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.port=1099 rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.authenticate=false rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.ssl=false rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.password.file= "%WMSCONFIG_HOME%/conf/jmxremote.password" rem set JMXOPTIONS=%JMXOPTIONS% -Dcom.sun.management.jmxremote.access.file= "%WMSCONFIG_HOME%/conf/jmxremote.access" rem log interceptor com.wowza.wms.logging.LogNotify - see Javadocs for ILogNotify %_EXESERVER% "%_EXECJAVA%" %JAVA_OPTS% %JMXOPTIONS% -Dcom.wowza.wms.AppHome="%WMSAPP_HOME%" -Dcom.wowza.wms.ConfigURL="%WMSCONFIG_URL%" -Dcom.wowza.wms.ConfigHome="%WMSCONFIG_HOME%" -cp %CLASSPATH% com.wowza.wms.bootstrap.Bootstrap start :end

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• java serialization problems with different JVMs

  - by Alberto

  I am having trouble using serialization in Java. I've searched the web for a solution but haven't found an answer yet. The problem is this - I have a Java library (I have the code and I export it to an archive prior to executing the code) which I need to use with two differents JVMs. One JVM is on the server (Ubuntu, running Java(TM) JRE SE Runtime Environment (build 1.7.0_09-b05)) and the other on Android 2.3.3. I compiled the library in Java 1.6. Now, I am trying to import to the client, an object exported from the server, but I receive this error: java.io.InvalidClassException: [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;; Incompatible class (SUID): [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;: static final long serialVersionUID =-359311387972759020L; but expected [Lweka.classifiers.functions.MultilayerPerceptron$NeuralEnd;: static final long serialVersionUID =1920571045915494592L; I do have an explicit serial version UID declared on the class MultilayerPerceptron$NeuralEnd, like this: protected class NeuralEnd extends NeuralConnection { private static final long serialVersionUID = 7305185603191183338L; } Where NeuralConnection implements the java.io.Serializable interface. If I do a serialver on MultilayerPerceptron$NeuralEnd I receive the serialVersionUID which I declared. So, why have both JVMs changed this value? Can you help me? Thanks, Alberto

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• Why is it a bad practice to call System.gc?

  - by zneak

  After answering to a question about how to force-free objects in Java (the guy was clearing a 1.5GB HashMap) with System.gc(), I've been told it's a bad practice to call System.gc() manually, but the comments seemed mitigated about it. So much that no one dared to upvote it, nor downvote it. I've been told there it's a bad practice, but then I've also been told garbage collector runs don't systematically stop the world anymore, and that it could also be only seen as a hint, so I'm kind of at loss. I do understand that usually the JVM knows better than you when it needs to reclaim memory. I also understand that worrying about a few kilobytes of data is silly. And I also understand that even megabytes of data isn't what it was a few years back. But still, 1.5 gigabyte? And you know there's like 1.5 GB of data hanging around in memory; it's not like it's a shot in the dark. Is System.gc() systematically bad, or is there some point at which it becomes okay? So the question is actually double: Why is it or not a bad practice to call System.gc()? Is it really a hint under certain implementations, or is it always a full collection cycle? Are there really garbage collector implementations that can do their work without stopping the world? Please shed some light over the various assertions people have made. Where's the threshold? Is it never a good idea to call System.gc(), or are there times when it's acceptable? If any, what are those times?

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• Restricting dynamically loaded classes and jars based on a security policy

  - by Max

  Hi, I would like to dynamically load a set of jars or classes (i.e. plugins loaded at runtime). At the same time, I would like to restrict what these plugins are able to do in the JVM. For a test case, I would like to restrict them to pretty much everything (right now I'm just allowing one System.getProperty value to be read). I am currently using a security policy file, but I'm having difficulty specifying a policy for one folder or package in my codeBase, but not another. Here is how my policy looks now: grant codeBase "file:/home/max/programming/java/plugin/plugins/" { permission java.util.PropertyPermission "java.version", "read"; }; grant codeBase "file:/home/max/programming/java/plugin/api/" { permission java.security.AllPermission; }; Where (for testing purposes), all files in the plugins package and folder are restricted, but the classes in the api folder are not. Is this possible? Do I have to create a custom class loader? Is there a better way to go about doing this? Thanks.

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• Why is my multithreaded Java program not maxing out all my cores on my machine?

  - by James B

  Hi, I have a program that starts up and creates an in-memory data model and then creates a (command-line-specified) number of threads to run several string checking algorithms against an input set and that data model. The work is divided amongst the threads along the input set of strings, and then each thread iterates the same in-memory data model instance (which is never updated again, so there are no synchronization issues). I'm running this on a Windows 2003 64-bit server with 2 quadcore processors, and from looking at Windows task Manager they aren't being maxed-out, (nor are they looking like they are being particularly taxed) when I run with 10 threads. Is this normal behaviour? It appears that 7 threads all complete a similar amount of work in a similar amount of time, so would you recommend running with 7 threads instead? Should I run it with more threads?...Although I assume this could be detrimental as the JVM will do more context switching between the threads. Alternatively, should I run it with fewer threads? Alternatively, what would be the best tool I could use to measure this?...Would a profiling tool help me out here - indeed, is one of the several profilers better at detecting bottlenecks (assuming I have one here) than the rest? Note, the server is also running SQL Server 2005 (this may or may not be relevant), but nothing much is happening on that database when I am running my program. Note also, the threads are only doing string matching, they aren't doing any I/O or database work or anything else they may need to wait on. Thanks in advance, -James

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• Do servlet containers prevent web applications from causing each other interference and how do they do it?

  - by chrisbunney

  I know that a servlet container, such as Apache Tomcat, runs in a single instance of the JVM, which means all of its servlets will run in the same process. I also know that the architecture of the servlet container means each web application exists in its own context, which suggests it is isolated from other web applications. As depicted here: Accepting that each web application is isolated, I would expect that you could create 2 copies of an identical web application, change the names and context paths of each (as well as any other relevant configuration), and run them in parallel without one affecting the other. The answers to this question appear to support this view. However, a colleague disagrees based on their experience of attempting just that. They took a web application and tried to run 2 separate instances (with different names etc) in the same servlet container and experienced issues with the 2 instances conflicting (I'm unable to elaborate more as I wasn't involved in that work). Based on this, they argue that since the web applications run in the same process space, they can't be isolated and things such as class attributes would end up being inadvertently shared. This answer appears to suggest the same thing The two views don't seem to be compatible, so I ask you: Do servlet containers prevent web applications deployed to the same container from conflicting with each other? If yes, How do they do this? If no, Why does interference occur? and finally, Under what circumstances could separate web applications conflict and cause each other interference?, perhaps scenarios involving resources on the file system, native code, or database connections?

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• What is best practice (and implications) for packaging projects into JAR's?

  - by user245510

  What is considered best practice deciding how to define the set of JAR's for a project (for example a Swing GUI)? There are many possible groupings: JAR per layer (presentation, business, data) JAR per (significant?) GUI panel. For significant system, this results in a large number of JAR's, but the JAR's are (should be) more re-usable - fine-grained granularity JAR per "project" (in the sense of an IDE project); "common.jar", "resources.jar", "gui.jar", etc I am an experienced developer; I know the mechanics of creating JAR's, I'm just looking for wisdom on best-practice. Personally, I like the idea of a JAR per component (e.g. a panel), as I am mad-keen on encapsulation, and the holy-grail of re-use accross projects. I am concerned, however, that on a practical, performance level, the JVM would struggle class loading over dozens, maybe hundreds of small JAR's. Each JAR would contain; the GUI panel code, necessary resources (i.e. not centralised) so each panel can stand alone. Does anyone have wisdom to share?

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• Modify Executing Jar file

  - by pinkynobrain

  Hello Stack Overflow friends. I have a simple problem which i fear doesnt have a simple solution and i need advice as to how to proceed. I am developing a java application packaged as and executable JAR but it requires to modify some of its JAR file contents during execution. At this stage i hit a problem because some OS lock the file preventing writes to it. It is essential that the user sees an updated version of the jar file by the time the application exits allthough i can be pretty flexible as to how to achieve this. A clean and efficient solution is obviously prefereable but portability is the only hard requirement. The following are three approaches i can see to solving the problem, feel free to comment on them or suggest others. Tell Java to unlock the JAR file for writing(this doesnt seem possible but it would be the easyest solution) Copy the executable class files to a tempory file on application startup, use a class loader to load these files and unload the ones from the initial JAR file.(Not had much experience with the classloaders but hopefully the JVM would then be smart enough to realize that the original JAR is nolonger in use and so unlock it) Put a Second executable JAR File inside the First, on startup extract the inner jar to e temporaryfile, invoke a new java process and pass it the location of the Outer JAR, first process exits, second process modifys the Outer jar unincumbered.(This will work but im not sure there is a platform independant way of one java app invoking another) I know this is a weird question but any help would be appreciated.

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• grails scaffolding broken

  - by damian

  Grails scaffoldin does not work in my grails application. When I go from the main page to the specific controller page it output something like this: Error 500: Servlet: default URI: /myapp/myDomain/list Exception Message: Tag [sortableColumn] is missing required attribute [title] or [titleKey] at /webTestDummyDomain/list:25 Caused by: Error processing GroovyPageView: Tag [sortableColumn] is missing required attribute [title] or [titleKey] at /myDomain/list:25 Class: /myDomain/list At Line: [25] Code Snippet: Code snippet empty. If I try to create a new app scaffold works perfectly. Additional data: Application Status * App version: 0.1 * Grails version: 1.2.2 * JVM version: 1.6.0_20 * Controllers: 11 * Domains: 10 * Services: 19 * Tag Libraries: 26 Installed Plugins * i18n - 1.2.2 * filters - 1.2.2 * logging - 1.2.2 * core - 1.2.2 * tomcat - 1.2.2 * webtest - 2.0.4 * functionalTest - 1.2.7 * yui - 2.7.0.1 * rest - 0.3 * jquery - 1.4.2.1 * bubbling - 2.1.2 * urlMappings - 1.2.2 * groovyPages - 1.2.2 * servlets - 1.2.2 * dataSource - 1.2.2 * controllers - 1.2.2 * codecs - 1.2.2 * jqueryUi - 1.8-SNAPSHOT * grailsUi - 1.2-SNAPSHOT * domainClass - 1.2.2 * mimeTypes - 1.2.2 * scaffolding - 1.2.2 * converters - 1.2.2 * hibernate - 1.2.2 * validation - 1.2.2 * services - 1.2.2 Can you give me any pointer?

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• Scala Interpreter scala.tools.nsc.interpreter.IMain Memory leak

  - by Peter

  I need to write a program using the scala interpreter to run scala code on the fly. The interpreter must be able to run an infinite amount of code without being restarted. I know that each time the method interpret() of the class scala.tools.nsc.interpreter.IMain is called, the request is stored, so the memory usage will keep going up forever. Here is the idea of what I would like to do: var interpreter = new IMain while (true) { interpreter.interpret(some code to be run on the fly) } If the method interpret() stores the request each time, is there a way to clear the buffer of stored requests? What I am trying to do now is to count the number of times the method interpret() is called then get a new instance of IMain when the number of times reaches 100, for instance. Here is my code: var interpreter = new IMain var counter = 0 while (true) { interpreter.interpret(some code to be run on the fly) counter = counter + 1 if (counter > 100) { interpreter = new IMain counter = 0 } } However, I still see that the memory usage is going up forever. It seems that the IMain instances are not garbage-collected by the JVM. Could somebody help me solve this issue? I really need to be able to keep my program running for a long time without restarting, but I cannot afford such a memory usage just for the scala interpreter. Thanks in advance, Pet

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• Create image from scratch with JMagick

  - by Michael IV

  I am using Java port of ImageMagick called JMagick .I need to be able to create a new image and write an arbitrary text chunk into it.The docs are very poor and what I managed to get so far is to write text into the image which comes from IO.Also , in all the examples I have found it seems like the very first operation ,before writing new image data , is always loading of an existing image into ImageInfo instance.How do I create an image from scratch with JMagick and then write a text into it? Here is what I do now : try { ImageInfo info = new ImageInfo(); info.setSize("512x512"); info.setUnits(ResolutionType.PixelsPerInchResolution); info.setColorspace(ColorspaceType.RGBColorspace); info.setBorderColor(PixelPacket.queryColorDatabase("red")); info.setDepth(8); BufferedImage img = new BufferedImage(512,512,BufferedImage.TYPE_4BYTE_ABGR); byte[] imageBytes = ((DataBufferByte) img.getData().getDataBuffer()).getData(); MagickImage mimage = new MagickImage(info,imageBytes); DrawInfo aInfo = new DrawInfo(info); aInfo.setFill(PixelPacket.queryColorDatabase("green")); aInfo.setUnderColor(PixelPacket.queryColorDatabase("yellow")); aInfo.setOpacity(0); aInfo.setPointsize(36); aInfo.setFont("Arial"); aInfo.setTextAntialias(true); aInfo.setText("JMagick Tutorial"); aInfo.setGeometry("+40+40"); mimage.annotateImage(aInfo); mimage.setFileName("text.jpg"); mimage.writeImage(info); } catch (MagickException ex) { Logger.getLogger(LWJGL_IDOMOO_SIMPLE_TEST.class.getName()).log(Level.SEVERE, null, ex); } It doesn't work , the JVM crashes with access violation as it probably expects for the input image from IO.

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• Eclipse does not start on Windows 7

  - by van

  Suddenly Eclipse today has decides to stop working. The last thing I did was close all perspectives and close Eclipse. When loading eclipse from the command prompt, using: "eclipse.exe -clean" the splash screen loads for a split second then exits. When I run the command: eclipsec -consoleLog -debug it results in the following output: Start VM: -Dosgi.requiredJavaVersion=1.6 -Dhelp.lucene.tokenizer=standard -Xms4096m -Xmx4096m -XX:MaxPermSize=512m -Djava.class.path=d:\devtools\eclipse\\plugins/org.eclipse.equinox.launcher_1.3. 0.v20130327-1440.jar -os win32 -ws win32 -arch x86_64 -showsplash d:\devtools\eclipse\\plugins\org.eclipse.platform_4.3.0.v20130605-20 00\splash.bmp -launcher d:\devtools\eclipse\eclipsec.exe -name Eclipsec --launcher.library d:\devtools\eclipse\\plugins/org.eclipse.equinox.launcher.win 32.win32.x86_64_1.1.200.v20130521-0416\eclipse_1503.dll -startup d:\devtools\eclipse\\plugins/org.eclipse.equinox.launcher_1.3.0.v201303 27-1440.jar --launcher.appendVmargs -product org.eclipse.epp.package.standard.product -consoleLog -debug -vm C:/Program Files/Java/jdk1.6.0_37/bin\..\jre\bin\server\jvm.dll -vmargs -Dosgi.requiredJavaVersion=1.6 -Dhelp.lucene.tokenizer=standard -Xms4096m -Xmx4096m -XX:MaxPermSize=512m -Djava.class.path=d:\devtools\eclipse\\plugins/org.eclipse.equinox.launcher_1.3. 0.v20130327-1440.jar Error occurred during initialization of VM Incompatible minimum and maximum heap sizes specified Checking Task Manager shows no Java process running and both the CPU and memory usage are very low. I have tried: Re-installing Eclipse Re-starting my machine But running eclipsec -consoleLog -debug from the command prompt still results in the issue: Error occurred during initialization of VM Incompatible minimum and maximum heap sizes specified

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• Standardizing a Release/Tools group on a specific language

  - by grahzny

  I'm part of a six-member build and release team for an embedded software company. We also support a lot of developer tools, such as Atlassian's Fisheye, Jira, etc., Perforce, Bugzilla, AnthillPro, and a couple of homebrew tools (like my Django release notes generator). Most of the time, our team just writes little plugins for larger apps (ex: customize workflows in Anthill), long-term utility scripts (package up a release for QA), or things like Perforce triggers (don't let people check into a specific branch unless their change description includes a bug number; authenticate against Active Directory instead of Perforce's internal passwords). That's about the scale of our problems, although we sometimes tackle something slightly more sizable. My boss, who is reasonably technical, has asked us to standardize on one or two languages so we can more easily substitute for each other. He's advocating bash scripts and Perl, due to their universality and simplicity. I can see his point--we mostly do "glue", so why not use "glue" languages rather than saddle ourselves with something designed for much larger projects? Since some of the tools we work with are Java-based, we do need to use something that speaks JVM sometimes. (The path of least resistance for these projects is BeanShell and Groovy.) I feel a tremendous itch toward language advocacy, but I'm trying to avoid saying "We should use Python 'cause I like it and Perl is gross." Instead, I'm trying to come up with a good approach to defining our problem set: what problems do we solve with scripts? Would we benefit from a library of common functions by our team, or are most of our projects more isolated? What is it reasonable to expect my co-workers to learn? What languages give us the most ease of development and ease of modification? Can you folks suggest some useful ways to approach this problem, both for my own thinking process and to help me facilitate some brainstorming among my coworkers?

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• Can't start the portable version of NetBeans 6.9.1 IDE

  - by Coder

  I downloaded the portable version of netbeans netbeans-6.9.1-201007282301-ml.zip from the netbeans site and changed the config file in etc/netbeans.conf as indicated on the netbeans site. The file contents are below. # ${HOME} will be replaced by JVM user.home system property #netbeans_default_userdir="${HOME}/.netbeans/6.9" netbeans_default_userdir=".netbeans/6.9" # Options used by NetBeans launcher by default, can be overridden by explicit # command line switches: netbeans_default_options="-J-client -J-Xss2m -J-Xms32m -J-XX:PermSize=32m -J-XX:MaxPermSize=200m -J-Dapple.laf.useScreenMenuBar=true -J-Dapple.awt.graphics.UseQuartz=true -J-Dsun.java2d.noddraw=true" # Note that a default -Xmx is selected for you automatically. # You can find this value in var/log/messages.log file in your userdir. # The automatically selected value can be overridden by specifying -J-Xmx here # or on the command line. # If you specify the heap size (-Xmx) explicitely, you may also want to enable # Concurrent Mark & Sweep garbage collector. In such case add the following # options to the netbeans_default_options: # -J-XX:+UseConcMarkSweepGC -J-XX:+CMSClassUnloadingEnabled -J-XX:+CMSPermGenSweepingEnabled # (see http://wiki.netbeans.org/wiki/view/FaqGCPauses) # Default location of JDK, can be overridden by using --jdkhome <dir>: #netbeans_jdkhome="/path/to/jdk" netbeans_jdkhome="C:\Program Files\Java\jdk1.6.0_24\" # Additional module clusters, using ${path.separator} (';' on Windows or ':' on Unix): #netbeans_extraclusters="/absolute/path/to/cluster1:/absolute/path/to/cluster2" # If you have some problems with detect of proxy settings, you may want to enable # detect the proxy settings provided by JDK5 or higher. # In such case add -J-Djava.net.useSystemProxies=true to the netbeans_default_options. But it refuses to start when i try to run it. If i change the JDK path to something incorrect it complains that it can't find the jdk so i think the jdk path is correct. It also creates a .netbeans directory when i try to start it. I don't see any errors and it just doesn't do anything else observable. Does anybody know how to set up this version of netbeans? Thanks.

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• jmap -histo is missing a lot of memory

  - by ripper234

  I have a JVM with 12 gigs of total RAM, out of which 7 GB is allocated to the old generation. There seems to be some memory leak, because almost the entire old gen is full, and will not release when I schedule a GC (the process is not doing anything else at that time). A jmap -histo dump only reveals less than 1 gigabyte worth of objects. Where are the missing 6 gigs? What better tool do you propose for diagnosing this? Here is the top of the jmap output: num #instances #bytes class name ---------------------------------------------- 1: 429853 68725736 <constMethodKlass> 2: 429853 51594040 <methodKlass> 3: 37503 49611368 <constantPoolKlass> 4: 37503 31109576 <instanceKlassKlass> 5: 191716 28019968 [C 6: 32573 26933152 <constantPoolCacheKlass> 7: 86158 13789560 [I 8: 53532 11244232 [B 9: 284 10507216 [J 10: 137608 7210664 <symbolKlass> 11: 203072 6498304 java.lang.String 12: 10132 5219512 <methodDataKlass> 13: 39694 4128176 java.lang.Class 14: 55713 3792816 [S 15: 61816 3141936 [[I 16: 90109 2883488 java.util.HashMap$Entry

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• Is it safe to reuse javax.xml.ws.Service objects

  - by Noel Ang

  I have JAX-WS style web service client that was auto-generated with the NetBeans IDE. The generated proxy factory (extends javax.xml.ws.Service) delegates proxy creation to the various Service.getPort methods. The application that I am maintaining instantiates the factory and obtains a proxy each time it calls the targetted service. Creating the new proxy factory instances repeatedly has been shown to be expensive, given that the WSDL documentation supplied to the factory constructor, an HTTP URI, is re-retrieved for each instantiation. We had success in improving the performance by caching the WSDL. But this has ugly maintenance and packaging implications for us. I would like to explore the suitability of caching the proxy factory itself. Is it safe, e.g., can two different client classes, executing on the same JVM and targetting the same web service, safely use the same factory to obtain distinct proxy objects (or a shared, reentrant one)? I've been unable to find guidance from either the JAX-WS specification nor the javax.xml.ws API documentation. The factory-proxy multiplicity is unclear to me. Having Service.getPort rather than Service.createPort does not inspire confidence.

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• Java performance issue

  - by Colby77

  Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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• How do I find Microsoft APIs?

  - by Stephen

  I'm a java programmer, and if I see something that: I don't know about or just want to find a method description without opening an ide or am on support I type java [classname] into google, and there it is. If I try this crazy stunt for C# I'll come up with a whole heap of tutorials (how do I use it etc). If I manage to get to MSDN, I have to wade through a page describing every .net technology to see how their syntax references the same object, and then I have to find the appropriate page from there ([class name] Constructor) for example. This is even more pronounced, because I don't have Visual Studio, so I've got nothing to make it easier. There must be something I'm missing or don't know... how does this situation work for Microsoft developers? how can I make my life easier/searches better? are there techniques that work no matter what computer I'm on (e.g. require no computer setup/downloads) Notes It could be thought that java is just "java", but it's just that the java apis are only referenced/defined in the core language. For all the other languages on the JVM, it's assumed that you will just learn the correct syntax to use the java apis. I presume that .Net only lists a whole heap of languages as the api classes are actually different and have different interfaces capabilities (or some approximation of this presumption). Edit While searching msdn works... in the java space I can type 'java [anyclass]' and it will generally be found... whether it's a java core api or a third party library

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• are there java based auto-updating tools other than WebStart & Eclipse P2?

  - by DaddyB

  Hi, I am working on a java based application and we are looking to ease our deployment of updates. Up until now, we've always simply sent out new install packs & had the sysadmin's on our customer sites roll out the upgrades - painful for a large number of users. what I'd like to do is something similar to java webstart (or eclipse p2) - when the application starts, it checks for updates in a specified location and then downloads the updates prior to starting. But here's my problem - I want more control over what's done outside of the scope of plugins & jar files. For example: I'd like to be able to upate my JVM (we ship a modified version with additional security features). I need to install DLL's - possibly local to the jar files, sometimes to windows Occasiontally run MSI's to install windows components (e.g. printer drivers). I need to modify config files & the registry. I have found a few applications that support this (such as AppLifeUpdate at http://www.kineticjump.com/) but they tend to be .NET focused and it seems a bit perverse to introduce a .NET dependancy on a java application ;) I know I could write my own here, but if there is already a 3rd party library out there that supports this kind of facility, then it would make my life a lot easier. So, has anyone else had a similar problem & knows of some products I could look at? Thanks, Brian.

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• Groovy / Scala / Java under the hood

  - by Jack

  I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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• .Net Remoting: Serialize Object and implementation

  - by flogo

  Hi, In my scenario there is a client-side assembly that contains a class (Task). This class implements an interface (ITask) that is known on the server. I'm trying to send a Task object from client to server without copying the assembly of the client manually to the server. If I just serialize the task object, the server obviously complains about the missing assembly. I then tried to serialze typeof(Task).Assembly but could not derserialize it on the server. Next I tried to File.ReadAllBytes(typeof(Task).Assembly.Location) and saved it to a temporary file on the server, which threw an exception on Assembly.LoadFrom(@".\temporary.dll"); Why am I doing this? Java RMI has a neat feature to request the implementation of an object that is received through remoting but is stil "unkown" (this JVM doesn't have the *.class file). This can be used for a compute server that just knows the interface of a "task" containing a run() method and downloads the implementation of this method on demand. This way the server doesn't have to be changed for new tasks. I'm trying to achieve something like this in .Net.

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• Yet another Haskell vs. Scala question

  - by Travis Brown

  I've been using Haskell for several months, and I love it—it's gradually become my tool of choice for everything from one-off file renaming scripts to larger XML processing programs. I'm definitely still a beginner, but I'm starting to feel comfortable with the language and the basics of the theory behind it. I'm a lowly graduate student in the humanities, so I'm not under a lot of institutional or administrative pressure to use specific tools for my work. It would be convenient for me in many ways, however, to switch to Scala (or Clojure). Most of the NLP and machine learning libraries that I work with on a daily basis (and that I've written in the past) are Java-based, and the primary project I'm working for uses a Java application server. I've been mostly disappointed by my initial interactions with Scala. Many aspects of the syntax (partial application, for example) still feel clunky to me compared to Haskell, and I miss libraries like Parsec and HXT and QuickCheck. I'm familiar with the advantages of the JVM platform, so practical questions like this one don't really help me. What I'm looking for is a motivational argument for moving to Scala. What does it do (that Haskell doesn't) that's really cool? What makes it fun or challenging or life-changing? Why should I get excited about writing it?

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