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  • Active - like-minded Java mailing lists

    - by Lewis Robbins
    I need to find an active Java mailing list, I have looked onto the GNU Java mailing list, to my surprise there had been not too much activity this month, it also focused on any GNU related Java - I'd really help me progress my Java ability, if I had an active, likeminded Java mailing list. Questions' that are not suited to Stackoverflow, or provide little benefit to any user that see's the question: discussing a new API change; best practices; open source discussion; trivia type questions on Java ArrayList boxining-unboxing; Community atmosphere. I also read Jon Skeets blog post about his previous Java/C# mailing lists examples - I did not catch any names, though I did they would be of benefit to me, if I had access to any of them.

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  • how to learn Java

    - by Sarang
    This question I am asking because I couldn't find any source which gives complete overview of java development. I just want to know where java technology currently in market & what is preferable for development ! Java always remain top programming language for development point of view. However, java is combo of, j2ee, j2me, jsp, jsf, spring, other frameworks, ui components, jndi, networking tools and various other "J" are there ! However, learning java is definitely dependent on the development requirement, but still, to be a well-experienced java developer, what is the organised way of learning java? What is preferable in current technology ? and what is deprecated, currently ?

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  • New Java Tutorials Updated

    - by hinkmond
    The new Java Tutorials are here! The new Java Tutorials are here! So what? So, you can read them on your iPad thingie--if that's how you roll, that is... See: Read New Java Tutorials Here's a quote: What's New The Java Tutorials are continuously updated to keep up with changes to the Java Platform and to incorporate feedback from our readers. Recent updates include the following features: The Generics lesson has been completely reworked... The Java Tutorials are now available in two ebook formats: mobi ebook files for Kindle. ePub ebook files for iPad, Nook, and other eReaders that support the ePub format. Just kick back, open up your favorite tablet or eReader and learn all about the new things in the Java platform. Nice. All you need now is a cool drink and you're all set! Hinkmond

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  • New to Java Programming - Error help

    - by JJJ
    I am going through a Java book and drafting the examples and have run into the following error when compiling this code. Any help would be appreciated thank you. Error: Main.java:3: class Addition is public, should be declared in a file named Addition.java public class Addition        ^ 1 error Code: import java.io.*; import java.util.Scanner; public class Addition {   public static void main(String[] args) { java.util.Scanner input = new java.util.Scanner(System.in);  int number1; int number2; int sum; System.out.print( "Enter first digit: " ); number1 = input.nextInt(); System.out.print( "Enter second digit:" ); number2 = input.nextInt(); sum = number1 + number2; System.out.printf( "Sum is %d\n, sum" );      } }

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  • From J2EE to Java EE: what has changed?

    - by Bruno.Borges
    See original @Java_EE tweet on 29 May 2014 Yeap, it has been 8 years since the term J2EE was replaced, and still some people refer to it (mostly recruiters, luckily!). But then comes the question: what has changed besides the name? Our community friend Abhishek Gupta worked on this question and provided an excellent response titled "What's in a name? Java EE? J2EE?". But let me give you a few highlights here so you don't lose yourself with YATO (yet another tab opened): J2EE used to be an infrastructure and resources provider only, requiring developers to depend on external 3rd-party frameworks to then implement application requirements or improve productivity J2EE used to require hundreds of XML lines of codes to define just a dozen of resources like EJBs, MDBs, Servlets, and so on J2EE used to support only EAR (Enterprise Archives) with a bunch of other archives like JARs and WARs just to run a simple Web application And so on, and so on! It was a great technology but still required a lot of work to get something up and running. Remember xDoclet? Remember Struts? The old days of pure Hibernate code? Or when Ajax became a trending topic and we were all implementing it with DWR Servlet? Still, we J2EE developers survived, and learned, and helped evolve the platform to a whole new level of DX (Developer Experience). A new DX for J2EE suggested a new name. One that referred to the platform as the Enterprise Edition of Java, because "Java is why we're here" quoting Bill Shannon. The release of Java EE 5 included so many features that clearly showed developers the platform was going after all those DX gaps. Radical simplification of the persistence model with the introduction of JPA Support of Annotations following the launch of Java SE 5.0 Updated XML APIs with the introduction of StAX Drastic simplification of the EJB component model (with annotations!) Convention over Configuration and Dependency Injection A few bullets you may say but that represented a whole new DX and a vision for upcoming versions. Clearly, the release of Java EE 5 helped drive the future of the platform by reducing the number of XMLs, Java Interfaces, simplified configurations, provided convention-over-configuration, etc! We then saw the release of Java EE 6 with even more great features like Managed Beans, CDI, Bean Validation, improved JSP and Servlets APIs, JASPIC, the posisbility to deploy plain WARs and so many other improvements it is difficult to list in one sentence. And we've gotta give Spring Framework some credit here: thanks to Rod Johnson and team, concepts like Dependency Injection fit perfectly into the Java EE Platform. Clearly, Spring used to be one of the most inspiring frameworks for the Java EE platform, and it is great to see things like Pivotal and Spring supporting JSR 352 Batch API standard! Cooperation to keep improving DX at maximum in the server-side Java landscape.  The master piece result of these previous releases is seen and called today as Java EE 7, which by providing a newly and improved JavaServer Faces release, with new features for Web Development like WebSockets API, improved JAX-RS, and JSON-P, but also including Batch API and so many other great improvements, has increased developer productivity and brought innovation to server-side Java developers. Java EE is not just a new name (which was introduced back in May 2006!) but a new Developer Experience for server-side Java developers. To show you why we are here and where we are going (see the Java EE 8 update), we wanted to share with you a draft of the new Java EE logos that the evangelist team created, to help you spread the word about Java EE. You can get access to these images at the Java EE Platform Facebook Album, or the Google+ Java EE Platform Album whichever is better for you, but don't forget to like and/or +1 those social network profiles :-) A message to all job recruiters: stop using J2EE and start using Java EE if you want to find great Java EE 5, Java EE 6, or Java EE 7 developers To not only save you recruiter valuable characters when tweeting that job opportunity but to also match the correct term, we invite you to replace long terms like "Java/J2EE" or even worse "#Java #J2EE #JEE" or all these awkward combinations with the only acceptable hashtag: #JavaEE. And to prove that Java EE is catching among developers and even recruiters, and that J2EE is past, let me highlight here how are the jobs trends! The image below is from Indeed.com trends page, for the following keywords: J2EE, Java/J2EE, Java/JEE, JEE. As you can see, J2EE is indeed going away, while JEE saw some increase. Perhaps because some people are just lazy to type "Java" but at the same time they are aware that J2EE (the '2') is past. We shall forgive that for a while :-) Another proof that J2EE is going away is by looking at its trending statistics at Google. People have been showing less and less interest in the term J2EE. See the chart below:  Recruiter, if you still need proof that J2EE is past, that Java EE is trending, and that other job recruiters are seeking for Java EE developers, and that the developer community is aware of the new term, perhaps these other charts can show you what term you should be using. See for example the Job Trends for Java EE at Indeed.com and notice where it started... 2006! 8 years ago :-) Last but not least, the Google Trends for Java EE term (including the still wrong but forgivable JavaEE term) shows us that the new term is catching up very well. J2EE is past. Oh, and don't worry about the curves going down. We developers like to be hipsters sometimes and today only AngularJS, NodeJS, BigData are going up. Java EE and other traditional server-side technologies such as Spring, or even from other platforms such as Ruby on Rails, PHP, Grails, are pretty much consolidated and the curves... well, they are consolidated too. So If you are a Java EE developer, drop that J2EE from your résumé, and let recruiters also know that this term is past. Embrace Java EE, and enjoy a new developer experience for server-side Java developers. Java EE on TwitterJava EE on Google+Java EE on Facebook

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  • Java RMI (Server: TCP Connection Idle/Client: Unmarshalexception (EOFException))

    - by Perry Dahl Christensen
    I'm trying to implement Sun Tutorials RMI application that calculates Pi. I'm having some serious problems and I cant find the solution eventhough I've been searching the entire web and several javaskilled people. I'm hoping you can put an end to my frustrations. The crazy thing is that I can run the application from the cmd on my desktop computer. Trying the exact same thing with the exact same code in the exact same directories on my laptop produces the following errors. The problem occures when I try to connect the client to the server. I don't believe that the error is due to my policyfile as I can run it on the desktop. It must be elsewhere. Have anyone tried the same and can you give me a hint as to where my problem is, please? POLICYFILE SERVER: grant { permission java.security.AllPermissions; permission java.net.SocketPermission"*", "connect, resolve"; }; POLICYFILE CLIENT: grant { permission java.security.AllPermissions; permission java.net.SocketPermission"*", "connect, resolve"; }; SERVERSIDE ERRORS: Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\STUDENTcd\ C:start rmiregistry C:java -cp c:\java;c:\java\compute.jar -Djava.rmi.server.codebase=file:/c:/jav a/compute.jar -Djava.rmi.server.hostname=localhost -Djava.security.policy=c:/jav a/servertest.policy engine.ComputeEngine ComputeEngine bound Exception in thread "RMI TCP Connection(idle)" java.security.AccessControlExcept ion: access denied (java.net.SocketPermission 127.0.0.1:1440 accept,resolve) at java.security.AccessControlContext.checkPermission(Unknown Source) at java.security.AccessController.checkPermission(Unknown Source) at java.lang.SecurityManager.checkPermission(Unknown Source) at java.lang.SecurityManager.checkAccept(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.checkAcceptPermi ssion(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.checkAcceptPermission(Unknown Sour ce) at sun.rmi.transport.Transport$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.rmi.transport.Transport.serviceCall(Unknown Source) at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Sou rce) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Sour ce) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source ) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) CLIENTSIDE ERRORS: Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\STUDENTcd\ C:java -cp c:\java;c:\java\compute.jar -Djava.rmi.server.codebase=file:\C:\jav a\files\ -Djava.security.policy=c:/java/clienttest.policy client.ComputePi local host 45 ComputePi exception: java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is: java.io.EOFException at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source) at sun.rmi.server.UnicastRef.invoke(Unknown Source) at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unkn own Source) at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source) at $Proxy0.executeTask(Unknown Source) at client.ComputePi.main(ComputePi.java:18) Caused by: java.io.EOFException at java.io.DataInputStream.readByte(Unknown Source) ... 6 more C: Thanks in advance Perry

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  • java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to X

    - by adisembiring
    Hi all, I'm using Hibernate 3.2.1 and database SQLServer2000 while I'm try to insert some data using my dao, some warning occurred like this: java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to BTN_SPP_DB at com.microsoft.jdbc.base.BaseWarnings.createSQLWarning(Unknown Source) at com.microsoft.jdbc.base.BaseWarnings.get(Unknown Source) at com.microsoft.jdbc.base.BaseConnection.getWarnings(Unknown Source) at org.hibernate.util.JDBCExceptionReporter.logAndClearWarnings(JDBCExceptionReporter.java:22) at org.hibernate.jdbc.ConnectionManager.closeConnection(ConnectionManager.java:443) at org.hibernate.jdbc.ConnectionManager.aggressiveRelease(ConnectionManager.java:400) at org.hibernate.jdbc.ConnectionManager.afterTransaction(ConnectionManager.java:287) at org.hibernate.jdbc.JDBCContext.afterTransactionCompletion(JDBCContext.java:221) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:119) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:43) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:1) at co.id.hanoman.btnmw.spp.dao.test.TagihanDaoTest.testSave(TagihanDaoTest.java:81) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99) at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75) at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45) at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66) at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35) at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196) my hibernate initialization log is: 2010-04-26 22:54:05,203 INFO [Version] Hibernate Annotations 3.3.0.GA 2010-04-26 22:54:05,234 INFO [Environment] Hibernate 3.2.1 2010-04-26 22:54:05,234 INFO [Environment] hibernate.properties not found 2010-04-26 22:54:05,234 INFO [Environment] Bytecode provider name : cglib 2010-04-26 22:54:05,234 INFO [Environment] using JDK 1.4 java.sql.Timestamp handling 2010-04-26 22:54:05,343 INFO [Configuration] configuring from resource: /hibernate.cfg.xml 2010-04-26 22:54:05,343 INFO [Configuration] Configuration resource: /hibernate.cfg.xml 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] trying to resolve system-id [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] recognized hibernate namespace; attempting to resolve on classpath under org/hibernate/ 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] located [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] in classpath 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.dialect=org.hibernate.dialect.SQLServerDialect 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.driver_class=com.microsoft.jdbc.sqlserver.SQLServerDriver 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.url=jdbc:microsoft:sqlserver://12.56.11.65:1433;databaseName=BTN_SPP_DB 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.username=spp 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.password=spp

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  • Java Generic Casting Type Mismatch

    - by Kay
    public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; public void main(String[] args){ int i; T[] arr = {1,3,4,5,2}; //ERROR HERE ******* foo } public T[] Heapsort(T[]anArray, int n){ // build initial heap T[]sortedArray = anArray; for (int i = n-1; i< 0; i--){ //assert: the tree rooted at index is a semiheap heapRebuild(anArray, i, n); //assert: the tree rooted at index is a heap } //sort the heap array int last = n-1; //invariant: Array[0..last] is a heap, //Array[last+1..n-1] is sorted for (int j=1; j<n-1;j++) { sortedArray[0]=sortedArray[last]; last--; heapRebuild(anArray, 0, last); } return sortedArray; } protected void heapRebuild(T[ ] items, int root, int size){ foo } } The error is on the line with "T[arr] = {1,3,4,5,2}" Eclispe complains that there is a: "Type mismatch: cannot convert from int to T" I've tried to casting nearly everywhere but to no avail.A simple way out would be to not use generics but instead just ints but that's sadly not an option. I've got to find a way to resolve the array of ints "{1,3,4,5,2}" into an array of T so that the rest of my code will work smoothly.

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  • What does this Java generics paradigm do and what is it called?

    - by Tom
    I'm looking at some Java classes that have the following form: public abstract class A <E extends A<E>> implements Comparable <E> { public final int compareTo( E other ) { // etc } } public class B extends A <B> { // etc } public class C extends A <C> { // etc } My usage of "Comparable" here is just to illustrate a possible use of the generic parameter "E". Does this usage of generics/inheritance have a name? What is it used for? My impression is that this allows the abstract class to provide a common implementation of a method (such as compareTo) without having to provide it in the subclasses. However, in this example, unlike an inherited method it would restrict subclasses to invoking compareTo on other instances of the same subclass, rather than any "A" subclass. Does this sound right? Anyway, just curious if any gurus out there have seen this before and know what it does. Thanks!

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  • Frustration with generics

    - by sbi
    I have a bunch of functions which are currently overloaded to operate on int and string: bool foo(int); bool foo(string); bool bar(int); bool bar(string); void baz(int p); void baz(string p); I then have a bunch of functions taking 1, 2, 3, or 4 arguments of either int or string, which call the aforementioned functions: void g(int p1) { if(foo(p1)) baz(p1); } void g(string p1) { if(foo(p1)) baz(p1); } void g(int p2, int p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); } void g(int p2, string p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); } void g(string p2, int p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); } void g(string p2, string p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); } // etc. (The implementation of the g() family is just a placeholder. actually they are more complicated.) More types than the current int or string might have to be introduced at any time. The same goes for functions with more arguments than 4. The current number of identical functions is barely manageable. Add one more variant in either dimension and the combinatoric explosion will be so huge, it might blow away the application. In C++, I'd templatize g() and be done. I understand that .NET generics are different. <sigh> But I have been fighting them for two hours trying to come up with a solution that doesn't involve too much copy&paste of code. To no avail. Surely, C#/.NET/generics/whatever won't require me to type out identical code for a family of functions taking five arguments of either of three types? So what am I missing here?

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  • Generics and anonymous type

    - by nettguy
    I understood,normally generics is for compile time safe and allow us to keep strongly typed collection.Then how do generic allow us to store anonymous types like List<object> TestList = new List<object>(); TestList.Add(new { id = 7, Name = "JonSkeet" }); TestList.Add(new { id = 11, Name = "Marc Gravell" }); TestList.Add(new { id = 31, Name = "Jason" });

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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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  • Spring to Java EE, Part Three - new tech article on otn/java

    - by Janice J. Heiss
    In a new article up on otn/java, Java EE expert David Heffelfinger continues his series exploring the relative strengths and weaknesses of Java EE and Spring. Here, he demonstrates how easy it is to develop the data layer of an application using Java EE, JPA, and the NetBeans IDE instead of the Spring Framework.In the first two parts of the series, he generated a complete Java EE application by using JavaServer Faces (JSF) 2.0, Enterprise JavaBeans (EJB) 3.1, and Java Persistence API (JPA) 2.0 from Spring’s Pet Clinic MySQL schema, thus showing how easy it is to develop an application whose functionality equaled that of the Spring sample application.In his new article, Heffelfinger tweaks the application to make it more user friendly.From the article:“The generated application displays primary keys on some of the pages, and these keys are surrogate primary keys—meaning that they have no business value and are used strictly as a unique identifier—so there is no reason why they should be visible to the user. In addition, we will modify some of the generated labels to make them more user-friendly.”He concludes the article with a summary:“The Java EE version of the application is not a straight port of the Spring version. For example, the Java EE version enables us to create, update, and delete veterinarians as well as veterinary specialties, whereas the Spring version of the application enables us only to view veterinarians and specialties. Additionally, the Spring version has a single page for managing/viewing owners, pets, and visits, whereas the Java EE version of the application has separate pages for each of these entities.The other thing we should keep in mind is that we didn’t actually write a lot of the code and markup for the Java EE version of the application, because the bulk of it was generated by the NetBeans wizard.” Have a look at the complete article here.

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  • Java Magazine????6? / Java Developer Newsletter

    - by sasa
    ??????????????????????9?26??Java Magazine????6??????????? ?6???????????????? ???????????????? ????? BlueJ??????????????????? Web????????????? ADAM BIEN??? HotSpot??? ??????JAVA????????????FORK/JOIN??????? javac??????? JavaFX 2??????????????????????·??????? ????????? ????????????????????????????? Oracle Berkeley DB Java Edition?Java API ConnectionPool.java????????? ?????????????????????????????????????????? ??????Java Developer Newsletter????????????Java????????????????????????????????????????????????????????????????????????????12?31?????????????1,000???Java??????Duke?????????????????????

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  • How to run Spring 3.0 PetClinic in tomcat with Hibernate backed JPA

    - by Zwei Steinen
    OK, this probably is supposed to be the easiest thing in the world, but I've been trying for the entire day, and it's still not working.. Any help is highly appreciated! What I did: Downloaded Tomcat 6.0.26 & Spring 3.0.1 Downloaded PetClinic from https://src.springframework.org/svn/spring-samples/petclinic Built & deployed petclinic.war. Ran fine with default TopLink persistence. Edited webapps/WEB-INF/spring/applicationContext-jpa.xml and changed jpaVendorAdaptor from TopLink to Hibernate. Edited webapps/WEB-INF/web.xml and changed context-param from applicationContext-jdbc.xml to applicationContext-jpa.xml Copied everything in the Spring 3.0.1 distribution to TOMCAT_HOME/lib. Launched tomcat. Saw Caused by: java.lang.IllegalStateException: ClassLoader [org.apache.catalina.loader.WebappClassLoader] does NOT provide an 'addTransformer(ClassFileTransformer)' method. Specify a custom LoadTimeWeaver or start your Java virtual machine with Spring's agent: -javaagent:spring-agent.jar Uncommented line <Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader"/> in webapps/META-INF/context.xml. Same error. Added that line to TOMCAT_HOME/context.xml Deployed without error. However, when I do something it will issue an error saying java.lang.NoClassDefFoundError: javax/transaction/SystemException at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:39) at org.hibernate.ejb.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:34) at org.springframework.orm.jpa.JpaTransactionManager.createEntityManagerForTransaction(JpaTransactionManager.java:400) at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:321) at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371) at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:336) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:102) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy34.findOwners(Unknown Source) at org.springframework.samples.petclinic.web.FindOwnersForm.processSubmit(FindOwnersForm.java:56) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doInvokeMethod(HandlerMethodInvoker.java:710) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:167) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:414) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:402) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:771) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:716) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:647) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:552) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:71) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.ClassNotFoundException: javax.transaction.SystemException at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1516) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1361) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 41 more I feel silly.. What am I missing?

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  • Netbeans with Oracle connection java.lang.ClassNotFoundException

    - by Attilah
    I use NetBeans 6.5 . When I try to run the following code : package com.afrikbrain.numeroteur16; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.logging.Level; import java.util.logging.Logger; /** * * @author */ public class NumeroteurTest { public NumeroteurTest() { } public void doIt() throws ClassNotFoundException{ try { Class.forName("oracle.jdbc.OracleDriver"); Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE","user","pwd"); String newNUMERO = new Numeroteur16("MATCLI", connection).numeroter(); System.out.println("NUMERO GENERE : "+newNUMERO.toString()); } catch (SQLException ex) { Logger.getLogger(NumeroteurTest.class.getName()).log(Level.SEVERE, null, ex); ex.printStackTrace(); } catch (NumException ex) { System.out.println(ex.getMessage()); ex.printStackTrace(); } } public static void main(String[] args){ try { new NumeroteurTest().doIt(); } catch (ClassNotFoundException ex) { Logger.getLogger(NumeroteurTest.class.getName()).log(Level.SEVERE, null, ex); System.out.println("Driver not found."); } } } when running it, I get this error : java.lang.ClassNotFoundException: oracle.jdbc.OracleDriver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at com.afrikbrain.numeroteur16.NumeroteurTest.doIt(NumeroteurTest.java:27) at com.afrikbrain.numeroteur16.NumeroteurTest.main(NumeroteurTest.java:45) Driver not found. how do I solve this problem ?

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  • Java Servlet: getInitParameter not work in Service()

    - by Gabriele
    I've added some parameters in my web.xml config file, as follow: <context-param> <param-name>service1</param-name> <param-value>http://www.example.com/example2.html</param-value> </context-param> <context-param> <param-name>service2</param-name> <param-value>http://www.example.com/example2.html</param-value> </context-param> ... I try to get the parameter in my servlet, in particular in my service method: protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println(this.getServletContext().getInitParameter("service1")); ... but at runtime I have a NullPointerException... How can I get the parameter value included in web.xml? This is the stacktrace: GRAVE: Servlet.service() for servlet DispatcherServlet threw exception java.lang.NullPointerException at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:160) at it.servlethope.DispatcherServlet.service(DispatcherServlet.java:66) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:176) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:145) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:92) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:381) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Unknown Source) DispatcherServlet.java:66 is the line where I try the getInitParameter()

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  • What would be different in Java if Enum declaration didn't have the recursive part

    - by atamur
    Please see http://stackoverflow.com/questions/211143/java-enum-definition and http://stackoverflow.com/questions/3061759/why-in-java-enum-is-declared-as-enume-extends-enume for general discussion. Here I would like to learn what exactly would be broken (not typesafe anymore, or requiring additional casts etc) if Enum class was defined as public class Enum<E extends Enum> I'm using this code for testing my ideas: interface MyComparable<T> { int myCompare(T o); } class MyEnum<E extends MyEnum> implements MyComparable<E> { public int myCompare(E o) { return -1; } } class FirstEnum extends MyEnum<FirstEnum> {} class SecondEnum extends MyEnum<SecondEnum> {} With it I wasn't able to find any benefits in this exact case. PS. the fact that I'm not allowed to do class ThirdEnum extends MyEnum<SecondEnum> {} when MyEnum is defined with recursion is a) not relevant, because with real enums you are not allowed to do that just because you can't extend enum yourself b) not true - pls try it in a compiler and see that it in fact is able to compile w/o any errors PPS. I'm more and more inclined to believe that the correct answer here would be "nothing would change if you remove the recursive part" - but I just can't believe that.

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  • Getting java.lang.ClassNotFoundException: com.mysql.jdbc.Driver Exception

    - by Yashwant Chavan
    Hi , I am getting Following Exception while configuring the Connection Pool in Tomcat This is Context.xml <Context path="/DBTest" docBase="DBTest" debug="5" reloadable="true" crossContext="true"> <!-- maxActive: Maximum number of dB connections in pool. Make sure you configure your mysqld max_connections large enough to handle all of your db connections. Set to -1 for no limit. --> <!-- maxIdle: Maximum number of idle dB connections to retain in pool. Set to -1 for no limit. See also the DBCP documentation on this and the minEvictableIdleTimeMillis configuration parameter. --> <!-- maxWait: Maximum time to wait for a dB connection to become available in ms, in this example 10 seconds. An Exception is thrown if this timeout is exceeded. Set to -1 to wait indefinitely. --> <!-- username and password: MySQL dB username and password for dB connections --> <!-- driverClassName: Class name for the old mm.mysql JDBC driver is org.gjt.mm.mysql.Driver - we recommend using Connector/J though. Class name for the official MySQL Connector/J driver is com.mysql.jdbc.Driver. --> <!-- url: The JDBC connection url for connecting to your MySQL dB. --> <Resource name="jdbc/TestDB" auth="Container" type="javax.sql.DataSource" maxActive="100" maxIdle="30" maxWait="10000" username="root" password="password" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql:///BUSINESS"/> </Context> This is Bean Entry <bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean"> <property name="jndiName" value="jdbc/TestDB"></property> <property name="resourceRef" value="true"></property> </bean> org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Co nnection; nested exception is org.apache.tomcat.dbcp.dbcp.SQLNestedException: Ca nnot load JDBC driver class 'com.mysql.jdbc.Driver' at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(Dat aSourceUtils.java:82) at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java: 382) at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:45 8) at org.springframework.jdbc.core.JdbcTemplate.query(JdbcTemplate.java:46 6) at com.businesscaliber.dao.Dao.getQueryForListMap(Dao.java:66) at com.businesscaliber.dao.MiscellaneousDao.getDefaultSucessStory(Miscel laneousDao.java:109) at com.businesscaliber.listeners.BusinessContextLoader.contextInitialize d(BusinessContextLoader.java:40) at org.apache.catalina.core.StandardContext.listenerStart(StandardContex t.java:3795) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4 252) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase .java:760) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:74 0) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:544) at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:831) at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:720 ) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:490 ) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1150) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java :311) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(Lifecycl eSupport.java:120) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1022) at org.apache.catalina.core.StandardHost.start(StandardHost.java:736) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443 ) at org.apache.catalina.core.StandardService.start(StandardService.java:4 48) at org.apache.catalina.core.StandardServer.start(StandardServer.java:700 ) at org.apache.catalina.startup.Catalina.start(Catalina.java:552) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl. java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces sorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433) Caused by: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot load JDBC driv er class 'com.mysql.jdbc.Driver' at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDat aSource.java:1136) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSo urce.java:880) at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(D ataSourceUtils.java:113) at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(Dat aSourceUtils.java:79) ... 30 more Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:164) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDat aSource.java:1130)

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  • Java Spotlight Episode 58: Peter Korn and Ofir Leitner on ME Accessibility

    - by Roger Brinkley
    Tweet Interview with Peter Korn and Ofir Leitner on Mobile and Embedded Accessibility. 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 Announcing Oracle WebLogic 12c Geronimo 3 beta - Another Apache project now compatible with Java EE 6 NetBeans 7.1 RC1 is out JavaFX links of the weeks JavaFX videos on Parleys: Nicolas Lorain's Introduction to JavaFX 2.0 from JavaOne 2011 & Richard Bair on JavaFX Architecture and Programming Model Events Dec 4, SOUJava Geek Bike Ride 2011, Sao Paulo  Dec 5-7, UKOUG, Birmingham, UK Dec 6-8, Java One Brazil, Sao Paulo Dec 9 UAIJUG, Uberlandia Dec 9 CEJUG, Fortaleza/CE Dec 10 GUJAVA, Florianopolis Dec 10 ALJUG, Maceio/AL Dec 11 Javaneiros, Campo Grande/MS Dec 12 GOJAVA, Goiania/GO Dec 13 RioJUG, Rio de Janeiro Feature interview Peter Korn is Oracle's Accessibility Principal – their senior individual contributor on accessibility. He is also Technical Manager of the AEGIS project, leading an EC-funded €12.6m investment building accessibility into future mainstream ICT (FP7-ICT224348). Mr. Korn co-developed and co-implemented the Java Accessibility API, and developed the Java Access Bridge for Windows. He helped design the open source GNOME Accessibility architecture found on most modern UNIX and GNU/Linux systems, and consulted on accessibility support for OpenOffice.org, Firefox, Thunderbird, and other applications. Prior to Sun/Oracle, Peter co-developed the outSPOKEN for Windows screen reader. Mr. Korn represented Sun/Oracle on TEITAC for the Section 508/255 refresh, co-led the OASIS ODF Accessibility subcommittee, and sits on INCITS V2 where he is contributing to ISO 13066: defining AT-IT interoperability standards including specifically the Java Accessibility API. Ofir Leitner is the architect of one of LWUIT's key features - the HTMLComponent which allows rendering HTML within LWUIT applications and to embed web-flows inside apps. Ofir is also responsible for LWUIT's bidirectional and RTL support and for the accessibility work that is being done these days in LWUIT. Mail Bag What's Cool Devoxx 2011 (Alexis) Eclipsecon Europe Talk by Andrew Overholt: IcedTea & IcedTea-Web Geek bike ride & Rio 500 Twitter followers @JavaSpotlight Show Transcripts Transcript for this show is available here when available.

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  • How to execute a Ruby file in Java, capable of calling functions from the Java program and receiving primitive-type results?

    - by Omega
    I do not fully understand what am I asking (lol!), well, in the sense of if it is even possible, that is. If it isn't, sorry. Suppose I have a Java program. It has a Main and a JavaCalculator class. JavaCalculator has some basic functions like public int sum(int a,int b) { return a + b } Now suppose I have a ruby file. Called MyProgram.rb. MyProgram.rb may contain anything you could expect from a ruby program. Let us assume it contains the following: class RubyMain def initialize print "The sum of 5 with 3 is #{sum(5,3)}" end def sum(a,b) # <---------- Something will happen here end end rubyMain = RubyMain.new Good. Now then, you might already suspect what I want to do: I want to run my Java program I want it to execute the Ruby file MyProgram.rb When the Ruby program executes, it will create an instance of JavaCalculator, execute the sum function it has, get the value, and then print it. The ruby file has been executed successfully. The Java program closes. Note: The "create an instance of JavaCalculator" is not entirely necessary. I would be satisfied with just running a sum function from, say, the Main class. My question: is such possible? Can I run a Java program which internally executes a Ruby file which is capable of commanding the Java program to do certain things and get results? In the above example, the Ruby file asks the Java program to do a sum for it and give the result. This may sound ridiculous. I am new in this kind of thing (if it is possible, that is). WHY AM I ASKING THIS? I have a Java program, which is some kind of game engine. However, my target audience is a bunch of Ruby coders. I don't want to have them learn Java at all. So I figured that perhaps the Java program could simply offer the functionality (capacity to create windows, display sprites, play sounds...) and then, my audience can simply code with Ruby the logic, which basically justs asks my Java engine to do things like displaying sprites or playing sounds. That's when I though about asking this.

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  • Auto convert java source to use generic rather than raw types

    - by Sam
    Is there a way/tool to auto convert Java source code from using raw types to using generic types? I have some legacy code with 677 references to raw types: ArrayList 47 Vector 420 Hashtable 61 Enumeration 64 Class 7 Iterator 78 TOTAL 677 Now I could manually look through the code to infer the generic types and replace, but that is going to take a long time.

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  • Java class object from type variable

    - by Alexander Temerev
    Is there a way to get Class object from the type variable in Java generic class? Something like that: public class Bar extends Foo<T> { public Class getParameterClass() { return T.class; // doesn't compile } } This type information is available at compile time and therefore should not be affected by type erasure, so, theoretically, there should be a way to accomplish this. Does it exist?

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