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• Using a JSON web service from a Java client application

  - by user383341

  I am developing a client-side Java application that has a bit of functionality that requires getting data from some web services that transmit in JSON (some RESTful, some not). No JavaScript, no web browser, just a plain JAR file that will run locally with Swing for the GUI. This is not a new or unique problem; surely there must be some open source libraries out there that will handle the JSON data transmission over HTTP. I've already found some that will parse JSON, but I'm having trouble finding any that will handle the HTTP communication to consume the JSON web service. So far I've found Apache Axis2 apparently which might have at least part of the solution, but I don't see enough documentation for it to know if it will do what I need, or how to use it. Maybe part of the problem is that I don't have experience with web services so I'm not able to know a solution when I see it. I hope some of you can point me in the right direction. Examples would be helpful.

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• Retrieving Large Lists of Objects Using Java EE

  - by hallidave

  Is there a generally-accepted way to return a large list of objects using Java EE? For example, if you had a database ResultSet that had millions of objects how would you return those objects to a (remote) client application? Another example -- that is closer to what I'm actually doing -- would be to aggregate data from hundreds of sources, normalize it, and incrementally transfer it to a client system as a single "list". Since all the data cannot fit in memory, I was thinking that a combination of a stateful SessionBean and some sort of custom Iterator that called back to the server would do the trick. How have you successfully solved this problem in the past?

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• Java Hibernate/C3P0 error: "Could not obtain connection metadata. An attempt by a client to checkout

  - by Allan

  I'm trying to get some code I was passed up and running. It appears to use the Hibernate framework. I've gotten past most of the errors tweaking the configuration, but this one has me dead stumped. It's trying to connect to two databases: gameapp and gamelog. Both exist. It seems to have issues connecting to gamelog, but none connecting to gameapp (later in the init, it connects to and loads other DBs just fine). Below, I've pasted the error and exception stack dump. I imaging there's something else in the configs, so I've also included the configuration file for that db. I know this is very vague, but I'm hoping some pro can see the stupid mistake I'm missing. <?xml version="1.0" encoding="GBK"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://127.0.0.1:3306/gamelog</property> <property name="connection.username">root</property> <property name="connection.password"></property> <property name="connection.useUnicode">true</property> <property name="connection.characterEncoding">UTF-8</property> <property name="hibernate.jdbc.batch_size">100</property> <property name="jdbc.fetch_size">1</property> <property name="hbm2ddl.auto">none</property><!-- update --> <property name="connection.useUnicode">true</property> <property name="show_sql">true</property> <!-- c3p0-configuration --> <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.min_size">5</property> <property name="hibernate.c3p0.max_size">10</property> <property name="hibernate.c3p0.timeout">30</property> <property name="hibernate.c3p0.idle_test_period">30</property> <property name="hibernate.c3p0.max_statements">0</property> <property name="hibernate.c3p0.acquire_increment">5</property> </session-factory> </hibernate-configuration> Exception and stack trace: 2010-04-30 17:50:00,411 WARN [org.hibernate.cfg.SettingsFactory] - Could not obtain connection metadata java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106) at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:65) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:527) at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128) at org.hibernate.connection.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:35) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:76) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:1933) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1216) at com.database.hibernate.util.HibernateFactory.<init>(Unknown Source) at com.database.hibernate.util.HibernateUtil.<clinit>(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.initBreedGoods(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl.access$000(Unknown Source) at com.server.databaseop.goodOp.GoodOpImpl$1.run(Unknown Source) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351) at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) Caused by: com.mchange.v2.resourcepool.TimeoutException: A client timed out while waiting to acquire a resource from com.mchange.v2.resourcepool.BasicResourcePool@ca470 -- timeout at awaitAvailable() at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1317) at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557) at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525) ... 18 more

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• AccessControlException: access denied - caller function failed to load properties file

  - by Michael Mao

  Hi all: I am having a jar archive environment which is gonna call my class in a folder like this: java -jar "emarket.jar" ../tournament 100 My compiled class is deployed into the ../tournament folder, this command runs well. After I changed my code to load a properties file, it gets the following exception message: Exception in thread "main" java.security.AccessControlException: access denied (java.io.FilePermission agent.properties read) 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.checkRead(Unknown Source) at java.io.FileInputStream.<init>(Unknown Source) at java.io.FileInputStream.<init>(Unknown Source) at Agent10479475.getPropertiesFromConfigFile(Agent10479475.java:110) at Agent10479475.<init>(Agent10479475.java:100) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at java.lang.Class.newInstance0(Unknown Source) at java.lang.Class.newInstance(Unknown Source) at emarket.client.EmarketSandbox.instantiateClientObjects(EmarketSandbox.java:92) at emarket.client.EmarketSandbox.<init>(EmarketSandbox.java:27) at emarket.client.EmarketSandbox.main(EmarketSandbox.java:166) I am wondering why this security checking will fail. I issue the getPropertitiesFromConfigFile() function inside my class's default constructor, like this: public class Agent10479475 extends AbstractClientAgent { //default constructor public Agent10479475() { //set all properties to their default values in constructor FT_THRESHOLD = 400; FT_THRESHOLD_MARGIN = 50; printOut("Now loading properties from a config file...", ""); getPropertiesFromConfigFile(); printOut("Finished loading",""); } private void getPropertiesFromConfigFile() { Properties props = new Properties(); try { props.load(new FileInputStream("agent.properties")); FT_THRESHOLD = Long.parseLong(props.getProperty("FT_THRESHOLD")); FT_THRESHOLD_MARGIN = Long.parseLong(props.getProperty("FT_THRESHOLD_MARGIN ")); } catch(java.io.FileNotFoundException fnfex) { printOut("CANNOT FIND PROPERTIES FILE :", fnfex); } catch(java.io.IOException ioex) { printOut("IOEXCEPTION OCCURED :", ioex); } } } My class is loading its own .properties file under the same folder. why would the Java environment complains about such a denial of access? Must I config the emarket.client.EmarketSandbox class, which is not written by me and stored inside the emarket.jar, to access my agent.properties file? Any hints or suggestions is much appreciated. Many thanks in advance.

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• Flat File Connection Manager in SSIS package shows "Valid File Name Must be Selected"

  - by Traples

  (Flat File Location) Samba Share | Windows Share (SSIS) _______________________________ | | XP 32bit | Works | Works | | 2003 Serv 32bit | Works | Works | | Vista 64bit | ERROR | Works | | Win 7 64bit | ERROR | Works | | 2008 Serv 64bit | ERROR | Works I created an SSIS package in VS 2008 that parses a flat file from a shared folder and puts the records into a SQL Server db. I recently installed Windows 7 and VS 2008 on a new workstation. When I import the package from TFS and open it, I get the error Validation error. Parse and Import Catalog Flat File: MySSISPackage: The file name "\\shared\flatfile.txt" specified in the connection was not valid. When I open the Flat File Connection Manager Editor, there is an error stating: A valid file name must be selected I can browse to and select the file from inside the editor, but I cannot change any properties, or move away from the General tab because of this error. If I go back to my laptop (Windows XP), where the package was first created, there is no error. Both workstations are on the same domain, and I'm logging in using the same credentials. Any ideas as to why I would receive this error from one workstation and not another? UPDATE: If I take the .dtsx package from the running workstation and load it into SSIS on the server, I get the following errors when it tries to run: Error: The file name "\\shared\flatfile.txt" specified in the connection was not valid. and... Error: Connection "MySSISPackage" failed validation. and... Error: The file name property is not valid. The file name is a device or contains invalid characters. UPDATE 2: a) The Shared folder I'm trying to pull the flat file from is a Samba share on a Unix box. b) If I access the file using SSIS on any 64-bit platform (Windows 7 64-bit, Vista 64-bit, Windows Server 2008) I get the error "A valid file name must be selected." c) Accessing the file using SSIS from 32-bit environments (Windows XP 32-bit, Windows Server 2003 32-bit) there is no problem. d) If I move the file to a shared folder on a Windows server, 64-bit SSIS recognizes the file.

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• Simple Java networking game engine [on hold]

  - by Florian Peschka

  I want to create a simple java networking game and search a networking engine that eases use of sockets etc. I have already read some questions on here and the internet about java networking for games, but many of them were over 10 years old or not really answered. I have no idea whatsoever about what exactly I need to send in terms of messages, but I figured simple strings or integers will be enough for my purposes. It's basically a peer to peer game, so I don't need a centralized server structure. Messaging doesn't have to have an extremely low ping, yet of course all players need to have a synchronized view. What are the possibilities I have here?

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• Open source Java CMS for Google App Engine?

  - by markvgti

  I am looking for an open source Java CMS (Web CMS, actually) to run on Google App Engine. I have looked at related older questions on this topic (What CMS runs on Google AppEngine?, CMS over Google App Engine, with SEO etc.) but the problem is that they all largely list Python-based CMSes. Plus these questions are pretty old, and since GAE is a fast-moving target, I thought it might be worthwhile to ask again. I want a CMS for creating some websites (for myself and for others), but would rather not start writing one from scratch. A "good" (very subjective, I know) open source WCMS allows me to start using a product, while still being able to add to/extend the product/project. On the one hand I am looking for a somewhat mature product/project, on the other hand it's easier to start contributing to the development cycle of a young product/project (conflicting, I know :-). Here are some features that would be preferable: [X]HTML/XML/CSS based templating Ability to create multiple blogs Galleries Ability to create a "Downloads" section (is this pretty much standard?) Separate management for digital assets (images, PDFs, binary files etc.) Roles like "Administrator", "Editor", "Contributor" etc. (or their equivalents) Ability to move/reorganize pages Export to PDF Reformat content for printing Is the CMS you are about to suggest especially well-suited to publishing an online book? My idea is that while the book may be offered as a downloadable eBook, the latest, most current version will be the one available on the website.

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• Java Spotlight Episode 84: Anil Gaur on JavaEE 7

  - by Roger Brinkley

  Tweet Interview with Anil Gaur, VP of Java Platform for Enterprise Edition and GlassFish Server, on JavaEE 7. Joining us this week on the Java All Star Developer Panel are Dalibor Topic, Java Free and Open Source Software Ambassador and 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 Tori Wieldt - Judges Selected for Duke's Choice Awards Donald Smith - #OpenJDK interview in Java Magazine Henrik Ståhl - Java 7 adoption at 23% JavaOne Kicks Off with Sunday Keynotes at Masonic Auditorium Jersey 2.0 M4 JSF 2.2 Latest Snapshot NetBeans IDE 7.2 - Deploy to Cloud Events May 30, OTN Java Developer Day, Redwood Shores 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 26-28, Jazoon, Zurich, Switzerland July 5, Java Forum, Stuttgart, Germany July 30-August 1, JVM Language Summit, Santa Clara Feature InterviewAnil Gaur is the Vice President of Java Platform, Enterprise Edition, and GlassFish Server at Oracle in the Fusion Middleware Group. Is responsible for creation of Java EE Specifications, Reference Implementation, and Compatibility Test Suites. Leading the evolution on Java EE into Cloud and PaaS environment through the Java EE 7 standard. Prior to that, managed the delivery of Java EE 6 Platform and SDK which quickly gained momentum in enterprise application development and deployments. In this episode we talk about GlassFish 3.1 release. Mail Bag What’s Cool RFR (L): Adding core file parsing on Mac OS X to SA Sergio Del Valle @swdelvalle is the 1,000 @JavaSpotlight twitter follower

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• Tech Article: Powerful Logging in Java ME

  - by OracleTechnologyNetwork

  Learn how to add logging to your Java ME MIDlets with Microlog, an open-source logging library.

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• How to specify file permission when putting a file using OpenSSH sftp command

  - by Adi Roiban

  I am using various SFTP clients for uploading files to an SFTP server and I have a problem with default permission used when putting files. When requesting to put a file, SFTP client like WinSCP or Filezilla will send the SSH_OPEN command without requesting any explicit file permission. On the other side, it looks like the OpenSSH sftp command on Linux (Red Hat and Ubuntu) is pending the SSH_OPEN command together with the '640' mode. How can I configure the OpenSSH command to not explictly set the file mode or how can I configure it to send a mode, other than 640? Many thanks! Update: I checked the OpenSSH sftp client source code and it looks like OpenSSH sftp will always tries to preserve file mode even if -P is not set: http://www.koders.com/c/fidD3B20680F615B33ACCB42398FAAFEE1C007DF942.aspx?s=rsa#L986 To solve this problem I used Putty SFTP client.

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• Java Transaction Service without the application server

  - by johnny

  Is it possible to have a Java standalone application (no application server attached) that exposes some operations that a client can call and be the one to manage the transactions? I was thinking this application to expose JNDI resources and get a hold of a java:comp/UserTransaction from there, get also a bean from there and call methods A, B and C on it and coordinate the transaction from the client? The application I'm writing isn't complex enough so that I need a big application server around it so I'm thinking to have a standalone JTS inside it that the client could interact with from a transactions point of view. I don't have much experience with distributed transactions and don't really know how to tackle the issue. Is it even possible? Am I getting myself into something beyond what a mere mortal (programmer) can handle? How can I approach this?

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• java.lang.ClassCastException: $Proxy99 cannot be cast

  - by svaret

  Hi, I am using JBoss4.2.2 and java6. The deployed ear's name is apa.ear In a servlet I have the following code line: placeBid = (PlaceBid) context.lookup("apa/" + PlaceBid.class.getSimpleName() + "/remote"); I have a generated jboss-app.xml like this: <jboss-app> <loader-repository>apa:app=ejb3</loader-repository> </jboss-app> When trying to get the PlaceBid via the context I get this exception java.lang.ClassCastException: $Proxy99 cannot be cast to se.nextit.actionbazaar.buslogic.PlaceBid The PlaceBid interface looks like this: @Remote public interface PlaceBid { Long addBid(String userId, Long itemId, Double bidPrice); } When I run the example coming with EJB3 in action it works. EJB3 in action sample code comes with ant building. I want to use Maven so I have rearranged the code some. However, I don't understan what I am doing wrong here. I have some thoughts about the jboss-app.xml file. I am not sure of how its content should look like. Grateful for any help. Best wishes Lasse

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• Feasibility to take over a JavaMe Project by Coders who have no experience in JavaMe

  - by Stephenmjm

  As the original JavaMe team will leave to do other items. The JavaMe project will be taken over by some guys knowing nothing about JavaMe. Transition period: One month About this JavaMe project: about 3.5 million lines of code (more than 180 java file, SourceCode is 8.5KB in total) using the Polish, Proguard document: The JavaMe project itself have no document. No UML map. Difficulties I guess: familiar with the JavaMe, this should be okay In order to do the further development. We need to Read the sourceCode ---- It's not easy to read 3.5 million lines of code having not enough comment Adaptation work for more than 100 phone These are the questions, thank you! In the case of our guys have no experience in JavaMe, Is one month too hasty? In order to take the job in time . What we should ask the original JavaMe team to do . Considering we hava no experience in JavaMe. The complication we taking the Adaptation work without the original JavaMe team? Any other suggestions?

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• ca-certificates-java fails to install

  - by Jonas

  I use a VPS with Ubuntu Server 10.10. I want to use Jetty and run the command sudo apt-get install jetty but it fails because the installation encounted errors while processing ca-certificates-java. I have tried to install the failed package with: sudo apt-get install ca-certificates-java How can I solve this? I have run sudo apt-get update and sudo apt-get upgrade but I get the same errors after that. I have also installed Ubuntu Server x64 on a VirtualBox, but the two Ubuntu Server 10.10 has different kernel versions (2.6.35 on VirtualBox and 2.6.18 on my VPS). And on VirtualBox I can install Jetty without any problems.

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• Eloqua API Full Code Example in JAVA

  - by Shawn Spencer

  Is there anyone out there who has mastered to retrieve some data programmatically from Eloqua? First of all, I'm more or less a newbie, as far as JAVA. I can follow tutorials, take directions and will Google till my fingers bleed. I understand the basics and am slightly familiar with OOP. My main problem is that I have a Friday deadline (and tomorrow is Thanksgiving). At any rate, all the Eloqua code snippets (that I've been able to find) illustrate one aspect of a specific issue, and that's it. In my case, I would greatly appreciate a JAVA project of some sort, with all the necessary files to do web services (WSDL, SOAP and perhaps WSIT) and the main class and all that included. No, I don't want you to do my work for me! Just give me enough to find my way around, enter the information I need to retrieve and all that. I'll take it from there. Any pointers, links or suggestions?

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• Java ExecutorService java heap space ptoblems

  - by Sergey Aganezov jr

  I have a little bit of a problem in a multitasking java department. I have a class, called public class ThreadWorker implements Runnable { //some code in here public void run(){ // invokes some recursion method in the ThreadWorker itself, // which will stop eventually { } all in all, pretty simple "worker" that can work on it's on. To work with threads I'm using public static int THREAD_NUMBER = 4; public static ExecutorServide es = Executors.newFixedThreadPool(THREAD_NUMBER); adding instances of ThreadWroker class happens here: public void recursiveMethod(Arraylist<Integers> elements, MyClass data){ if (elements.size() == 0 && data.qualifies()){ ThreadWorker tw = new ThreadWorker(data); es.execute(tw); return; } for (int i=0; i< elements.size(); i++){ // some code to prevent my problem MyClass data1 = new MyClass(data); MyClass data2 = new MyClass(data); ArrayList<Integer> newElements = (ArrayList<Integer>)elements.clone(); data1.update(elements.get(i)); data2.update(-1 * elements.get(i)); newElements.remove(i); recursiveMethod(newElements, data1); recursiveMethod(newElements, data2); { } and the problem is that the depth of the recursion tree is quite big, so as it's width, so a lot of ThreadWorkers are added to the ExecutorService, so after some time on the big input a get Exception in thread "pool-1-thread-2" java.lang.OutOfMemoryError: Java heap space which is caused, as I think because of a ginormous number of ThreadWorkers i'm adding to ExecutorSirvice to be executed, so it runs out of memory. Every ThreadWorker takes about 40 Mb of RAM for all it needs. Is there a method to get how many threads (instances of classes implementing runnable interface) have been added to ExecutorService? So I can add it in the shown above code (int the " // some code to prevent my problem"), as while ("number of threads in the ExecutorService" > 10){ Thread.sleep(10000); } so I won't go to deep or to broad with my recursion and prevent those exception-throwing situations. Sincerely, Sergey Aganezov jr.

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• Question about casting a class in Java with generics

  - by Florian F

  In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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• File and Printer Sharing, in 10.0.0.x

  - by bubbles2

  Hi, I have a strange problem: When I assign addresses of the form 10.0.0.x to my computers, file sharing (smb) does not work. When I assign them addresse of the form 192.168.1.x it works... OS is XP SP3, for subnetmasks i tried both 255.255.255.0 and 255.0.0.0 Any ideas what I can do? [EDIT] I forgot to add: pinging doesn't work either

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• Java: volatile guarantees and out-of-order execution

  - by WizardOfOdds

  Note that this question is solely about the volatile keyword and the volatile guarantees: it is not about the synchronized keyword (so please don't answer "you must use synchronize" for I don't have any issue to solve: I simply want to understand the volatile guarantees (or lack of guarantees) regarding out-of-order execution). Say we have an object containing two volatile String references that are initialized to null by the constructor and that we have only one way to modify the two String: by calling setBoth(...) and that we can only set their references afterwards to non-null reference (only the constructor is allowed to set them to null). For example (it's just an example, there's no question yet): public class SO { private volatile String a; private volatile String b; public SO() { a = null; b = null; } public void setBoth( @NotNull final String one, @NotNull final String two ) { a = one; b = two; } public String getA() { return a; } public String getB() { return b; } } In setBoth(...), the line assigning the non-null parameter "a" appears before the line assigning the non-null parameter "b". Then if I do this (once again, there's no question, the question is coming next): if ( so.getB() != null ) { System.out.println( so.getA().length ); } Am I correct in my understanding that due to out-of-order execution I can get a NullPointerException? In other words: there's no guarantee that because I read a non-null "b" I'll read a non-null "a"? Because due to out-of-order (multi)processor and the way volatile works "b" could be assigned before "a"? volatile guarantees that reads subsequent to a write shall always see the last written value, but here there's an out-of-order "issue" right? (once again, the "issue" is made on purpose to try to understand the semantics of the volatile keyword and the Java Memory Model, not to solve a problem).

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• Java Cryptography Extension

  - by Adam Tannon

  I was told that in order to support AES256 encryption inside my Java app that I would need the JCE with Unlimited Strength Jurisdiction Policy Files. I downloaded this from Oracle and unzipped it and I'm only seeing 2 JARs: local_policy.jar; and US_export_polic.jar I just want to confirm I'm not missing anything here! My understanding (after reading the README.txt) is that I just drop these two into my <JAVA_HOME>/lib/security/ directory and they should be installed. By the names of these JARs I have to assume that its not the Java Crypto API that cannot handle AES256, but it's in fact a legal issue, perhaps? And that these two JARs basically tell the JRE "yes, it's legally-acceptable to run this level of crypto (AES256)." Am I correct or off-base?

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• FileNotFound exception when trying to write to a file

  - by Chris Knight

  OK, I'm feeling like this should be easy but am obviously missing something fundamental to file writing in Java. I have this: File someFile = new File("someDirA/someDirB/someDirC/filename.txt"); and I just want to write to the file. However, while someDirA exists, someDirB (and therefore someDirC and filename.txt) do not exist. Doing this: BufferedWriter writer = new BufferedWriter(new FileWriter(someFile)); throws a FileNotFoundException. Well, er, no kidding. I'm trying to create it after all. Do I need to break up the file path into components, create the directories and then create the file before instantiating the FileWriter object?

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• Resources for game networking in Java

  - by pudelhund

  I am currently working on a Java multiplayer game. The game itself (single player) already works perfectly fine and so does the chat. The only thing that is really missing is the multiplayer part. Sadly I am absolutely clueless on where to start with that. I roughly know that I will have to work with packages, and I also know many things about streaming etc (chat is already working). Oh and it should - according to this article - be a UDP server. My problem is that I can't find any resources on how to do this. A tutorial (book or website) would be perfect, alternatively a good example of an open source client/server (in Java of course) would be fine as well. If you feel like doing something helpful I'd also really appreciate someone "privately" teaching me via email or some chat program :) Thank you!

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• Can't decide between Java or Python for college [on hold]

  - by Will Harrison

  I'm returning to college in about a month for Computer Science. My problem is, I have been programming on the web since I left (4 years ago), using PHP, ASP.NET, and JavaScript. I want to bone up on a more general purpose language that is cross platform before I begin. I would also like to be using a language that is common at my school and I know that they teach the students C++, Java, and Python. I would like to choose between Java or Python but I'm not sure which one. What do you think would be better based on job prospects in the next 2 years and community?

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• DI/IoC in Java for a .NET'er used to Castle.Windsor

  - by Ciddan

  Is there a Java DI container that works in a similar way to the most excellent Castle.Windsor container on the .NET side? The Java containers I've had a look at all seem to rely on annotations (Guice) within my services, which I don't dig all that much - I'd like to go POJO all the way if possible. Spring on the other hand can do without the annotations, but it requires a lot of XML. XML configuration != maintainability. One of the really nice things about Castle.Windsor is the wiring you're able to set up in code with Installers, auto wiring based on naming conventions and whatnot. Ideally the container should also support lifecycle management and configuration; i.e. registering components as transient, singleton, pooled etc. Another bonus would be support for interceptors. Any tips would be greatly appreciated.

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• java 2D and swing

  - by user384706

  Hi, I have trouble understanding a fundamental concept in Java 2D. To give a specific example: One can customize a swing component via implementing it's own version of the method paintComponent(Graphics g) Graphics is available to the body of the method. Question: What is exactly this Graphics object, I mean how it is related to the object that has the method paintComponent? Ok, I understand that you can do something like: g.setColor(Color.GRAY); g.fillOval(0, 0, getWidth(), getHeight()); To get a gray oval painted. What I can not understand is how is the Graphics object related to the component and the canvas. How is this drawing actually done? Another example: public class MyComponent extends JComponent { protected void paintComponent(Graphics g) { System.out.println("Width:"+getWidth()+", Height:"+getHeight()); } public static void main(String args[]) { JFrame f = new JFrame("Some frame"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setSize(200, 90); MyComponent component = new MyComponent (); f.add(component); f.setVisible(true); } } This prints Width:184, Height:52 What does this size mean? I have not added anything to the frame of size(200,90). Any help on this is highly welcome Thanks

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