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  • Installed Java 7, but terminal still shows Java 6

    - by chipbk10
    I've installed Java 7 on my Mac (10.7.5), but in the terminal there is still java 6. java version "1.6.0_37" Java(TM) SE Runtime Environment (build 1.6.0_37-b06-434-11M3909) Java HotSpot(TM) 64-Bit Server VM (build 20.12-b01-434, mixed mode) There will be no problem with the version 6 on terminal, if I always got that errors when I tried to install a java application (LatexDraw): : CGContextGetCTM: invalid context 0x0 : CGContextSetBaseCTM: invalid context 0x0 : CGContextGetCTM: invalid context 0x0 : CGContextSetBaseCTM: invalid context 0x0 The problem is related to instability of java 6 inferred from this link I've read this installed-java-7-on-mac-osx-but-terminal-is-still-using-version-6 and also try to change my Java version by using export JAVA_HOME="/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home", but in my folder /System/Library/Frameworks/JavaVM.framework/Versions, there is no version 1.7, only versions under 1.6 ??? So, how can I fix this issue?

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  • Netgear VPN can't access specific server

    - by Critologist
    I have a Netgear FVS318N configured with a VPN. I'm trying to access my call recorder with the provided software from another office. I've already setup the VPN connection, and it works. I can connect and ping the remote router and a few other things on the network. However, I can't ping or connect to my call recorder. If I move outside of the office network (i.e. connect directly to the cable modem or via a mobile hotspot), I can connect and ping the call recorder just fine. The office has a simple Linksys WRT54G router and is using AT&T Uverse. The remote location is using Charter Cable with a Netgear FVS318N. Has anyone ever encountered anything like this before? I've setup an identical VPN previously for a different client using similar hardware and never encountered this. Thanks in advance!

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  • Windows Java-based apps not working

    - by DariusVE
    After updating the Java JRE to 7u25, many Java-based applications not works as usual, the I upgrade Java to 7u45, and still the apps not working. Minecraft start screen not showing, have to press TAB key to select the Run button and press ENTER to run the game. Netbeans IDE it's running, but none it's showing on the screen. Eclipse and JDownloader are working fine. I cannot run the Java Control Panel, it's only shows the Java icon at the taskbar. My System OS: Windows 7 Ultimate SP1 64Bits Java: java version "1.7.0_45" Java(TM) SE Runtime Environment (build 1.7.0_45-b18) Java HotSpot(TM) Client VM (build 24.45-b08, mixed mode, sharing)

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  • Why can't I connect to a wifi network with my laptop, when I can with my phone?

    - by Alex Sf.
    I can connect with my phone and use the browser as usual. On my laptop it won't connect when using windows 7 while in ubuntu it will connect, but with no internet. What is going on here and how can I get internet on my laptop ? [edit] It's a public wifi hotspot. I can connect with no issues at home. My network asapter is: Atheros AR5B97. And my phone is an iPhone 3G. The wizard's of no help since it asks me to check the router, which I can't since it's a public hostspot.

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  • Command output as string

    - by rik
    I want to get output from command C:\Program Files (x86)\Java\jre7\bin\java.exe" -version as string variable. I tried this way: $out = &"C:\Program Files (x86)\Java\jre7\bin\java.exe" -version but it gives error message: java.exe : java version "1.7.0_05" At line:1 char:9 + $out = & <<<< "C:\Program Files (x86)\Java\jre7\bin\java.exe" -version + CategoryInfo : NotSpecified: (java version "1.7.0_05":String) [], RemoteException + FullyQualifiedErrorId : NativeCommandError Java(TM) SE Runtime Environment (build 1.7.0_05-b05) Java HotSpot(TM) Client VM (build 23.1-b03, mixed mode, sharing) $out variable seems empty. What am I doing wrong?

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  • how to uninstall the jdk 1.7.0 in the ubuntu

    - by kaiwii ho
    i encounter a very strange problem,and here is the detail: i'm going to uninstall the jdk 1.7.0.but when i use the rpm to check the appropriate name of the package,it prompt nothing.Anyway,when i use the command java -version,it will prompt the detail of the jdk 1.7.0. below is the detail: root@kaiwiiho:/usr/java# rpm -qa|grep jdk root@kaiwiiho:/usr/java# java -version java version "1.7.0" Java(TM) SE Runtime Environment (build 1.7.0-b147) Java HotSpot(TM) Server VM (build 21.0-b17, mixed mode) root@kaiwiiho:/usr/java# rpm -qa|grep jdk root@kaiwiiho:/usr/java# so what happen?And how can i uninstall it?thx

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  • How can I access a Web server in a VM from an iPad?

    - by Nick Haslam
    I have a virtual machine (running Windows Server 2012, if it's relevant), on VMware Workstation. It is running an Apache Tomcat web server, and I'm wanting to access that webserver from an iPad. Is this feasible, or even possible ? I have tried running Connectify Hotspot on the host machine, but that only gets me as far as being able to access a webpage on the host machine. It doesn't look to pass the connection through to the VM as they are on different subnets. Any thoughts are gratefully received.

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  • Can the JVM(Oracle) run into an OutOfMemory error if the heap size is below the max?

    - by user439407
    I am running a Tomcat site(with an NGinx front end) that seems to be randomly running out of memory even though the max heap size is pretty large. My question is is it possible for the JVM to get an OutOfMemory error even if the heap size is significantly less than -Xmx? For instance, here is a snapshot I took just 15 seconds before an OutOfMemory error: Tue Dec 18 23:13:28 JST 2012 Free memory: 162.31 MB Total memory: 727.75 MB Max memory: 3808.00 MB I guess theoretically it's possible that my code generated 3 gigs worth of objects in 15 seconds, but I highly doubt it. It seems like the JVM was unable to grow the heap even though it theoretically had room....Is it possible that other processes started using memory to the point that the JVM could not grow? I am running 64-bit Oracle Hotspot on a 64 bit vm running CentOS 5 with 6 gigs of ram.

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  • Public Wi-Fi and software updates

    - by coding4fun
    According to Microsoft, "Never update your software on a public Internet connection." So I have some questions. 1. What if a public Wi-Fi hotspot is the only Internet available, ever? Never update anything? 2. What happens if Windows or some other program is set to update automatically and attempts to do so while you are using a public Wi-Fi? Disable all automatic updates on all software? 3. Will VPN help to secure software updates? If so, how to go about it? Thanks.

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  • Logins with only HTTP - are they as insecure as I'm thinking?

    - by JoeCool1986
    Recently I was thinking about how websites like gmail and amazon use HTTPS during the login process when accessing your account. This makes sense, obviously, since you're typing in your account username and password and you would want that to be secure. However, on Facebook, among countless other websites, their logins are done with simple HTTP. Doesn't that mean that my login name and password are completely unencrypted? Which, even worse, means that all those people who login to their facebooks (or similar sites) at a wifi hotspot in public are susceptible to anyone getting their credentials using a simple packet sniffer (or something similar)? Is it really that easy? Or am I misunderstanding internet security? I'm a software engineer working on some web related stuff, and although at the current time I'm not too involved with the security aspect of our software, I knew I should probably know the answer to this question, since it's extremely fundamental to website security. Thanks!

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  • I need to make Windows 7 STOP disabling the wifi adapter when the wired LAN is connected

    - by Escobar Ceaser
    This is a Dell Latitude E6430. There is a setting in the bios to control this behavior and I have DISABLED it but it still happens. I am also running the latest bios. When I plug in a network cable the wifi adapter becomes disabled. I need it to stay enabled. What else could be making this happen? EDIT: The reason I need to do this is because with NETSH WLAN commands you can create a wifi hotspot by sharing the internet connection on the wired adapter and broadcasting a ssid on the virtual wifi nic. I do this all the time but it's not working on this laptop. I'm wondering if it's a network security thing where I am. I'm going to try from my hotel tonight and report back.

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  • Upgrade to java 1.7 in eclipse on mac

    - by user2159614
    I'm sort of a beginner with eclipse but I want to update the libraries or build path or whatever to java 1.7 from java 1.6 and I can't figure it out. I'm a computer science student at the university of washington and various TA's and students have tried to figure out this problem but it's stumped them all. I've installed java 1.7 from Oracle a few times already and the java section of system preferences says I have 1.7 but java -version in terminal says: java version "1.6.0_41" Java(TM) SE Runtime Environment (build 1.6.0_41-b02-445-11M4107) Java HotSpot(TM) 64-Bit Server VM (build 20.14-b01-445, mixed mode) What's going on here? My mac is totally up to date on everything else

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  • Java Spotlight Episode 86: Tony Printezis on Garbage Collection First

    - by Roger Brinkley
    Interview with Tony Printezis on Garbage Collection First (GC1). Joining us this week on the Java All Star Developer Panel is Arun Gupta, Java EE Guy. 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 JSR 358: A major revison of the Java Community Process - JCP 3.Next JAX-RS 2.0 Early Draft- Third Edition Events June 11-14, Cloud Computing Expo, New York City June 12, Boulder JUG June 13, Denver JUG June 13, Eclipse Juno DemoCamp, Redwoood Shore June 13, JUG Münster June 14, Java Klassentreffen, Vienna, Austria June 18-20, QCon, New York City June 19, CJUG, Chicago June 20, 1871, Chicago June 26-28, Jazoon, Zurich, Switzerland Jun 27, Houston JUG ?? July 5, Java Forum, Stuttgart, Germany Jul 13-14, IndicThreads, Delhi July 30-August 1, JVM Language Summit, Santa Clara Feature InterviewTony Printezis is a Principal Member of Technical Staff at Oracle, based in Burlington, MA. He has been contributing to the Java HotSpot Virtual Machine since 2006. He spends most of his time working on dynamic memory management for the Java platform, concentrating on performance, scalability, responsiveness, parallelism, and visualization of garbage collectors. He obtained a Ph.D. in 2000 and a BSc (Hons) in 1995, both from the University of Glasgow in Scotland. In addition, he is a JavaOne Rock Star, a title awarded for his highly rated JavaOne session on GC. Mail Bag What’s Cool JavaOne content selection is complete. Notifications done.

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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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  • EclipseCon 2011

    - by Marcus Hirt
    I sadly could not make it to EclipseCon last year. It was sad for so many reasons, not the least being that Sweden during that part of the year is cold and dark. ;) This year, however, I will be contributing two talks: ---> HotRockit – What to Expect from Oracle’s Converged JVM Oracle is converging the HotSpot and JRockit JVMs to produce a "best of breed JVM". Internally the project is sometimes referred to as the HotRockit project. There is already a large influx of ideas and solutions provided by the JRockit JVM into the Open JDK. Examples of improvements include: Better monitoring and profiling Improved performance Better ergonomics This talk will discuss what to expect from the converged JVM over the next two years, and how this will benefit the Eclipse community. Production-time Problem Solving in Eclipse This session will look at some common problems and pitfalls in Java applications. The focus will be on non-invasive profiling and diagnostics of running production systems. Problems tackled will be: Excessive GC Finding hotspots and optimizing them Optimizing the choice of data structures Synchronization problems Finding out where exceptions are thrown Finding memory leaks All problems will be demonstrated and solved running both the bad-behaving applications and the tools to analyze them from within the Eclipse Java IDE. <--- I hope to meet you there!

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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  • The biggest ADF conference "down under"

    - by Chris Muir
    While Oracle Open World is the place to be for ADF presentations, for Aussies living in Perth, San Francisco is a tad far away (believe me from experience, the 23hrs flight from PER-SYD-SFO is tedious).  That's why I'm very excited to see that the Australian Oracle User Group at this year's Perth conference is running its largest set of ADF presentation to date: 5! Okay, it doesn't compare to the 60 ADF sessions at OOW, but it's a small conference of around 300 people that runs for 2 days with 54 sessions total, not 40000 people that runs for 5 days with 1900+ sessions, so I think that's a good effort for a conference that's at the end of the earth! What's even better about this year's conference, is the AUSOUG conference is moving away from just consultants and Oracle staff presenting, but will also include customers presenting on ADF too.  This again proves Perth is a little ADF hotspot, which puts a tear to an ADF product manager's eye let me tell you ;-) The ADF sessions will include: Kevin Payne - JWH Group - ADF Mobile Application Development Matthew Carrigy - Department of Finance Western Australia - The times, they are a-changin’ - An Oracle Forms to JDeveloper ADF  Case Study Penny Cookson & Chris Noonan - Sage Computing Services - Impress your bosses with JDeveloper ADF dashboards on their iPads ...oh and... Chris Muir - Oracle Corporation - Speed-Dating Oracle JDeveloper 12c and Oracle ADF New Features  Chris Muir - Oracle Corporation - Develop Mobile Apps for Smart Devices: Converging Web and Native Applications You can check out the conference schedule here.  I hope you'll support these ADF presenters by attending the AUSOUG Perth conference, I look forward to seeing you there.

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  • Screwed up terminal after modifying bashrc

    - by omgzor
    I ended up screwing up my terminal, while setting up Sbt for the Coursera Scala course. I can't summon gedit (or anything else) anymore. I get the following error: Command 'gedit' is available in '/usr/bin/gedit' The command could not be located because '/usr/bin' is not included in the PATH environment variable. Also, each new instance of Terminal writes these messages before any command is written: -bash: :/home/antonio/jdk7/jdk1.7.0_07/bin: No such file or directory -bash: export: `/home/antonio/Desktop/Scala/install/sbt/bin:/home/antonio/jdk7/jdk1.7.0_07/bin': not a valid identifier I recently did a manual installation of the jdk 7, which apparently works: java -version java version "1.7.0_07" Java(TM) SE Runtime Environment (build 1.7.0_07-b10) Java HotSpot(TM) 64-Bit Server VM (build 23.3-b01, mixed mode) While setting up Sbt, I made the mistake of editing bashrc by writing gedit ~/.bashrc on my terminal instead of writing gedit .bashrc, I wrote the following lines at the end of the bashrc file that opened: export PATH=/PATH/TO/YOUR/jdk1.7.0-VERSION/bin:$PATH export PATH=/home/antonio/jdk7/jdk1.7.0_07/bin:$PATH What is wrong here? How can I access my bashrc file and modify it again?

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  • Pointer position way off in Java Application menu's when using gnome-shell

    - by Hailwood
    When using any java application in gnome-shell if the window is maximised the pointer position is way off; but only on the menu's, in the editor, or the side panel, the pointer is fine. This only presents itself when the window is maximized, and it seems that the further away from 0x0 the window is when you maximise it, the bigger the pointer offset. From what I have gathered it has to do with the window not updating it's size when it gets maximised. The other issue is that when a gnome-shell notification appears, when clicking on it, I lose the ability to type in the editor, I can select text etc, but can't give it focus to type. I must bring up some other text input (e.g. right click on a file on the left, select rename, which brings up a rename dialog) after that I can type in the editor again. So, how can I fix this? Below is as much information as I can think to provide $ gnome-shell --version GNOME Shell 3.6.1 $ java -version java version "1.7.0_09" Java(TM) SE Runtime Environment (build 1.7.0_09-b05) Java HotSpot(TM) 64-Bit Server VM (build 23.5-b02, mixed mode) $ file /etc/alternatives/java /etc/alternatives/javac /etc/alternatives/java: symbolic link to '/usr/lib/jvm/java-7-oracle/jre/bin/java' /etc/alternatives/javac: symbolic link to '/usr/lib/jvm/java-7-oracle/bin/javac'

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  • Talking JavaOne with Rock Star Charles Nutter

    - by Janice J. Heiss
    JavaOne Rock Stars, conceived in 2005, are the top rated speakers from the JavaOne Conference. They are awarded by their peers who through conference surveys recognize them for their outstanding sessions and speaking ability. Over the years many of the world’s leading Java developers have been so recognized.We spoke with distinguished Rock Star, Charles Nutter. A JRuby Update from Charles NutterCharles Nutter of Red Hat is well known as a lead developer of JRuby, a Ruby implementation of Java that is tightly integrated with Java to allow for the embedding of the interpreter into any Java application with full two-way access between the Java and the Ruby code. Nutter is giving the following sessions at this year’s JavaOne: CON7257 – “JVM Bytecode for Dummies (and the Rest of Us Too)” CON7284 – “Implementing Ruby: The Long, Hard Road” CON7263 – “JVM JIT for Dummies” BOF6682 – “I’ve Got 99 Languages, but Java Ain’t One” CON6575 – “Polyglot for Dummies” (Both with Thomas Enebo) I asked Nutter, to give us the latest on JRuby. “JRuby seems to have hit a tipping point this past year,” he explained, “moving from ‘just another Ruby implementation’ to ‘the best Ruby implementation for X,’ where X may be performance, scaling, big data, stability, reliability, security, and a number of other features important for today's applications. We're currently wrapping up JRuby 1.7, which improves support for Ruby 1.9 APIs, solves a number of user issues and concurrency challenges, and utilizes invokedynamic to outperform all other Ruby implementations by a wide margin. JRuby just gets better and better.” When asked what he thought about the rapid growth of alternative languages for the JVM, he replied, “I'm very intrigued by efforts to bring a high-performance JavaScript runtime to the JVM. There's really no reason the JVM couldn't be the fastest platform for running JavaScript with the right implementation, and I'm excited to see that happen.”And what is Nutter working on currently? “Aside from JRuby 1.7 wrap-up,” he explained, “I'm helping the Hotspot developers investigate invokedynamic performance issues and test-driving their new invokedynamic code in Java 8. I'm also starting to explore ways to improve the general state of dynamic languages on the JVM using JRuby as a guide, and to help the JVM become a better platform for all kinds of languages.”

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  • Talking JavaOne with Rock Star Charles Nutter

    - by Janice J. Heiss
    JavaOne Rock Stars, conceived in 2005, are the top rated speakers from the JavaOne Conference. They are awarded by their peers who through conference surveys recognize them for their outstanding sessions and speaking ability. Over the years many of the world’s leading Java developers have been so recognized.We spoke with distinguished Rock Star, Charles Nutter. A JRuby Update from Charles NutterCharles Nutter of Red Hat is well known as a lead developer of JRuby, a Ruby implementation of Java that is tightly integrated with Java to allow for the embedding of the interpreter into any Java application with full two-way access between the Java and the Ruby code. Nutter is giving the following sessions at this year’s JavaOne: CON7257 – “JVM Bytecode for Dummies (and the Rest of Us Too)” CON7284 – “Implementing Ruby: The Long, Hard Road” CON7263 – “JVM JIT for Dummies” BOF6682 – “I’ve Got 99 Languages, but Java Ain’t One” CON6575 – “Polyglot for Dummies” (Both with Thomas Enebo) I asked Nutter, to give us the latest on JRuby. “JRuby seems to have hit a tipping point this past year,” he explained, “moving from ‘just another Ruby implementation’ to ‘the best Ruby implementation for X,’ where X may be performance, scaling, big data, stability, reliability, security, and a number of other features important for today's applications. We're currently wrapping up JRuby 1.7, which improves support for Ruby 1.9 APIs, solves a number of user issues and concurrency challenges, and utilizes invokedynamic to outperform all other Ruby implementations by a wide margin. JRuby just gets better and better.” When asked what he thought about the rapid growth of alternative languages for the JVM, he replied, “I'm very intrigued by efforts to bring a high-performance JavaScript runtime to the JVM. There's really no reason the JVM couldn't be the fastest platform for running JavaScript with the right implementation, and I'm excited to see that happen.”And what is Nutter working on currently? “Aside from JRuby 1.7 wrap-up,” he explained, “I'm helping the Hotspot developers investigate invokedynamic performance issues and test-driving their new invokedynamic code in Java 8. I'm also starting to explore ways to improve the general state of dynamic languages on the JVM using JRuby as a guide, and to help the JVM become a better platform for all kinds of languages.” Originally published on blogs.oracle.com/javaone.

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  • internet sharing over wifi between ubuntu 11.10 and windows7

    - by Vivek Pradhan
    So i have looked up a lot of forums for these solution but haven't really found one that works. I have a laptop running ubuntu 11.10 connected to the ethernet cord at home and i want to share the internet over wifi with my friend's laptop running windows7. I did not think it would be so difficult, I tried a lot of things: I went to networks and then wireless and set up a wifi hotspot, my laptop got connected to it and the ipv4 was set to "shared to other computers". Thankfully the network was discoverable and after some tries my friend was able to connect to the network, but it still showed that there was no internet access. I tried coniguring the tcp addresses of the wifi on his laptop. Bottom line: did not work. I went to the network manager, clicked on create a new wireless network, created one with security WEP 40/128 bit passphrase, tried the other 2 options later, and did the same thing as with the wifi, this network was also not discoverable initially and after some tries, we could connect to it but then ICS was not working although there was a working internet on my ubuntu laptop. I would really appreciate if some one who has faced a similar problem and got it fixed to please give me a step by step solution of how to get this work, because this is a prety common problem with ubuntu distros I have noticed. Note: This however seems to work with ubuntu to ubuntu connections, but specifically cross OS connections like windows or my phone running android ICS are not able to see or if connect not able to share internet on my laptop

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  • Why so Long time span in creating Session Factory?

    - by vijay.shad
    Hi My project is web application running in the tomcat container. This application is a spring framework based hibernate application. The problem with this is it takes a lot of time when creates session factory. here is the logs 2010-04-15 23:05:28,053 DEBUG [SessionFactoryImpl] Session factory constructed with filter configurations : {} 2010-04-15 23:05:28,053 DEBUG [SessionFactoryImpl] instantiating session factory with properties: {java.vendor=Sun Microsystems Inc., sun.java.launcher=SUN_STANDARD, catalina.base=/usr/local/InstalledPrograms/apache-tomcat-6.0.20, sun.management.compiler=HotSpot Tiered Compilers, catalina.useNaming=true, os.name=Linux, sun.boot.class.path=/usr/java/jdk1.6.0_17/jre/lib/resources.jar:/usr/java/jdk1.6.0_17/jre/lib/rt.jar:/usr/java/jdk1.6.0_17/jre/lib/sunrsasign.jar:/usr/java/jdk1.6.0_17/jre/lib/jsse.jar:/usr/java/jdk1.6.0_17/jre/lib/jce.jar:/usr/java/jdk1.6.0_17/jre/lib/charsets.jar:/usr/java/jdk1.6.0_17/jre/classes, java.util.logging.config.file=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/conf/logging.properties, java.vm.specification.vendor=Sun Microsystems Inc., hibernate.generate_statistics=true, java.runtime.version=1.6.0_17-b04, hibernate.cache.provider_class=org.hibernate.cache.EhCacheProvider, user.name=root, shared.loader=, tomcat.util.buf.StringCache.byte.enabled=true, hibernate.connection.release_mode=auto, user.language=en, java.naming.factory.initial=org.apache.naming.java.javaURLContextFactory, sun.boot.library.path=/usr/java/jdk1.6.0_17/jre/lib/i386, java.version=1.6.0_17, java.util.logging.manager=org.apache.juli.ClassLoaderLogManager, user.timezone=Canada/Pacific, sun.arch.data.model=32, java.endorsed.dirs=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/endorsed, sun.cpu.isalist=, sun.jnu.encoding=UTF-8, file.encoding.pkg=sun.io, package.access=sun.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper.,sun.beans., file.separator=/, java.specification.name=Java Platform API Specification, java.class.version=50.0, user.country=US, java.home=/usr/java/jdk1.6.0_17/jre, java.vm.info=mixed mode, os.version=2.6.18-128.el5, path.separator=:, java.vm.version=14.3-b01, hibernate.jdbc.batch_size=25, java.awt.printerjob=sun.print.PSPrinterJob, sun.io.unicode.encoding=UnicodeLittle, package.definition=sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper., java.naming.factory.url.pkgs=org.apache.naming, sun.rmi.dgc.client.gcInterval=3600000, user.home=/root, java.specification.vendor=Sun Microsystems Inc., java.library.path=/usr/java/jdk1.6.0_17/jre/lib/i386/server:/usr/java/jdk1.6.0_17/jre/lib/i386:/usr/java/jdk1.6.0_17/jre/../lib/i386:/usr/java/packages/lib/i386:/lib:/usr/lib, java.vendor.url=http://java.sun.com/, java.vm.vendor=Sun Microsystems Inc., hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect, sun.rmi.dgc.server.gcInterval=3600000, common.loader=${catalina.home}/lib,${catalina.home}/lib/*.jar, java.runtime.name=Java(TM) SE Runtime Environment, java.class.path=:/usr/local/InstalledPrograms/apache-tomcat-6.0.20/bin/bootstrap.jar, hibernate.bytecode.use_reflection_optimizer=false, java.vm.specification.name=Java Virtual Machine Specification, java.vm.specification.version=1.0, catalina.home=/usr/local/InstalledPrograms/apache-tomcat-6.0.20, sun.cpu.endian=little, sun.os.patch.level=unknown, hibernate.cache.use_query_cache=true, hibernate.connection.provider_class=org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider, java.io.tmpdir=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/temp, java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi, server.loader=, os.arch=i386, java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment, java.ext.dirs=/usr/java/jdk1.6.0_17/jre/lib/ext:/usr/java/packages/lib/ext, user.dir=/, line.separator=, java.vm.name=Java HotSpot(TM) Server VM, hibernate.cache.use_second_level_cache=true, file.encoding=UTF-8, java.specification.version=1.6, hibernate.show_sql=true} 2010-04-15 23:08:53,516 DEBUG [AbstractEntityPersister] Static SQL for entity: com.vsd.model.Order There you can see the time delay of more than 3 mins in executing these processes. My database is mysql and database server is running on the local machine only. The container environment is Centos Linux system. I am clueless about why it takes that much of time in executing these process, But when i do the same task from under eclipse it does not take that much of time. Development environment is Windows.

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  • Java Not Recognized As Default Application

    - by John
    I just installed java according to this article, and 'java -version' displays java version "1.7.0_07" Java(TM) SE Runtime Environment (build 1.7.0_07-b10) Java HotSpot(TM) 64-Bit Server VM (build 23.3-b01, mixed mode) 'update-alternatives --config java' returns this: There are 2 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/bin/gij-4.6 1046 auto mode 1 /usr/bin/gij-4.6 1046 manual mode * 2 /usr/local/java/jdk1.7.0_07/bin/java 1 manual mode Press enter to keep the current choice[*], or type selection number: with update-alternatives --config javac (or javaws) returning similarly. however java isn't listed in the default applications menu when I click on a .jar file and go to "open with application". I tried to install java this way, and on the update-alternatives part of the command returned me: /etc/alternatives/[java,javac,javaws] is dangling, it will be updated with best choice I just confirmed that I can use java, as 'java -jar file.jar' does work. Just figured that I'd mention it, don't know why I didn't before, but when I right click on a .jar file, java 7 run-time isn't even listed there, it seems that the file-manager isn't recognizing it as a program, but it is there, and it does work...

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