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• NoClassDefFoundError points to the wrong class.

  - by Sora

  I'm validating the installation of a program that consists of a few separate modules. They are not co-dependent. I have apple.jar and orange.jar, they are placed in the same folder and were developed in the same project, but run independent of each other. Running apple.jar goes fine, but orange.jar gives me a NoClassDefFoundError pointing to apple.jar. /usr/java/jre1.6.0_14/bin/java -jar validator.jar Exception in thread "main" java.lang.NoClassDefFoundError: orange/client/Apple Caused by: java.lang.ClassNotFoundException: orange.client.Apple at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClassInternal(Unknown Source) Could not find the main class: validator/client/StormDataXMLGenerator. Program will exit. The manifest file lists Orange as the correct main class. Main-Class: orange/client/Orange Anybody know why it's giving me the NoClassDefFoundError? Thanks in advance!

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• Custom event listener on Android app

  - by Bilthon

  Hi everybody, I need to set up a simple event listener to refresh a listview from once in a while. The problem is I don't know how could I generate an event. I know that for events like key or button pressing I just need to implement the handler. But in this specific case I actually need to generate the event, which will be fired everytime another running thread of my app wakes up and refreshes it's list of news from a rss feed. I've done everything, but got stucked in here. Can I get any suggestion or link with some more info on how to implement this? Thanks Nelson R. Perez

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• 2008 Datacenter Word Automation issue

  - by Brad

  We have an application that uses word automation. It works fine under Windows XP, but does not work on our Windows Server 2008 64-bit virtual machine running on VMware ESX unless it is running as the domain administrator. Under any other account (including a local admin), Word starts, uses a lot of CPU for 40 seconds when opening a document, and then just hangs. Our application does not access anything not on the local machine, and this machine is not being used for anything else (not a domain controller, etc). I know others have posted similar issues, with the solution of creating a Desktop folder somewhere under the windows directory. We did this, and it did not solve the problem (Word did not get as far as it did before we did this though). Please don't turn this into a thread about why I am trying to do this, whether I should do this, or whether I need to. For argument sake, I don't need to do this, but understanding what privilege a local admin does not have that is needed to do this is a legitimate concern.

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• Can I mix compile time string comparison with MPL templates?

  - by Negative Zero

  I got this compile time string comparison from another thread using constexpr and C++11 (http://stackoverflow.com/questions/5721813/compile-time-assert-for-string-equality). It works with constant strings like "OK" constexpr bool isequal(char const *one, char const *two) { return (*one && *two) ? (*one == *two && isequal(one + 1, two + 1)) : (!*one && !*two); } I am trying to use it in the following context: static_assert(isequal(boost::mpl::c_str<boost::mpl::string<'ak'>>::value, "ak"), "should not fail"); But it gives me an compilation error of static_assert expression is not an constant integral expression. Can I do this?

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• Can JNI handle any dll files (Windows)?

  - by henry

  I am new to JNI. And have a few questions : Can JNI handle every type dll exists in windows? I wanted to link a library but it gives me error. Is it possible JNI and the dll are not compatible? Excerpt from VB .NET (It works) Private Declare Function ConnectReader Lib "rfidhid.dll" () As Integer Private Declare Function DisconnectReader Lib "rfidhid.dll" () As Integer Private Declare Function SetAntenna Lib "rfidhid.dll" (ByVal mode As Integer) As Integer Full Code From Java public class MainForm { /** * @param args */ public native int ConnectReader(); public static void main(String[] args) { // TODO Auto-generated method stub MainForm mf = new MainForm(); System.out.println(mf.ConnectReader()); } static { System.loadLibrary("rfidhid"); } } Error code shown Exception in thread "main" java.lang.UnsatisfiedLinkError: MainForm.ConnectReader()I at MainForm.ConnectReader(Native Method) at MainForm.main(MainForm.java:13) Can anyone point to me where I might do wrong

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• Server Emulator Design Pattern

  - by adisembiring

  I wanna build server socket emulator, but I want implement some design pattern there. I will described my case study that I have simplified like these: My Server Socket will always listen client socket. While some request message come from the client socket, the server emulator will response the client through the socket. the response is response code. '00' will describe request message processed successfully, and another response code expect '00' will describe there are some error while processing the message request. IN the server there are some UI, this UI contain check response parameter such as. response code timeout interval While the server want to response the client message, the response code taken from input parameter response form UI check the timeout interval, it will create sleep thread and the interval taken from timeout interval input from UI. I have implement the function, but I create it in one class. I feel it so sucks. Can you suggest me what class / interface that I must create to refactor my code.

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• Database file is inexplicably locked during SQLite commit

  - by sweeney

  Hello, I'm performing a large number of INSERTS to a SQLite database. I'm using just one thread. I batch the writes to improve performance and have a bit of security in case of a crash. Basically I cache up a bunch of data in memory and then when I deem appropriate, I loop over all of that data and perform the INSERTS. The code for this is shown below: public void Commit() { using (SQLiteConnection conn = new SQLiteConnection(this.connString)) { conn.Open(); using (SQLiteTransaction trans = conn.BeginTransaction()) { using (SQLiteCommand command = conn.CreateCommand()) { command.CommandText = "INSERT OR IGNORE INTO [MY_TABLE] (col1, col2) VALUES (?,?)"; command.Parameters.Add(this.col1Param); command.Parameters.Add(this.col2Param); foreach (Data o in this.dataTemp) { this.col1Param.Value = o.Col1Prop; this. col2Param.Value = o.Col2Prop; command.ExecuteNonQuery(); } } this.TryHandleCommit(trans); } conn.Close(); } } I now employ the following gimmick to get the thing to eventually work: private void TryHandleCommit(SQLiteTransaction trans) { try { trans.Commit(); } catch (Exception e) { Console.WriteLine("Trying again..."); this.TryHandleCommit(trans); } } I create my DB like so: public DataBase(String path) { //build connection string SQLiteConnectionStringBuilder connString = new SQLiteConnectionStringBuilder(); connString.DataSource = path; connString.Version = 3; connString.DefaultTimeout = 5; connString.JournalMode = SQLiteJournalModeEnum.Persist; connString.UseUTF16Encoding = true; using (connection = new SQLiteConnection(connString.ToString())) { //check for existence of db FileInfo f = new FileInfo(path); if (!f.Exists) //build new blank db { SQLiteConnection.CreateFile(path); connection.Open(); using (SQLiteTransaction trans = connection.BeginTransaction()) { using (SQLiteCommand command = connection.CreateCommand()) { command.CommandText = DataBase.CREATE_MATCHES; command.ExecuteNonQuery(); command.CommandText = DataBase.CREATE_STRING_DATA; command.ExecuteNonQuery(); //TODO add logging } trans.Commit(); } connection.Close(); } } } I then export the connection string and use it to obtain new connections in different parts of the program. At seemingly random intervals, though at far too great a rate to ignore or otherwise workaround this problem, I get unhandled SQLiteException: Database file is locked. This occurs when I attempt to commit the transaction. No errors seem to occur prior to then. This does not always happen. Sometimes the whole thing runs without a hitch. No reads are being performed on these files before the commits finish. I have the very latest SQLite binary. I'm compiling for .NET 2.0. I'm using VS 2008. The db is a local file. All of this activity is encapsulated within one thread / process. Virus protection is off (though I think that was only relevant if you were connecting over a network?). As per Scotsman's post I have implemented the following changes: Journal Mode set to Persist DB files stored in C:\Docs + Settings\ApplicationData via System.Windows.Forms.Application.AppData windows call No inner exception Witnessed on two distinct machines (albeit very similar hardware and software) Have been running Process Monitor - no extraneous processes are attaching themselves to the DB files - the problem is definitely in my code... Does anyone have any idea whats going on here? I know I just dropped a whole mess of code, but I've been trying to figure this out for way too long. My thanks to anyone who makes it to the end of this question! brian UPDATES: Thanks for the suggestions so far! I've implemented many of the suggested changes. I feel that we are getting closer to the answer...however... The code above technically works however it is non-deterministic! It is not guaranteed to do anything aside from spin in neutral forever. In practice it seems to work somewhere between the 1st and 10th iteration. If i batch my commits at a reasonable interval damage will be mitigated but I really do not want to leave things in this state... More suggestions welcome!

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• List of files and libraries that Window SDK contains?

  - by AKN

  For developing programs for windows, we need windows SDK. I understand that this SDK is what helps to create windows and handle window events and all that. I suppose it also enables us to manipulate with files and registries. (Does the same SDK is the reason for thread creation and handling?) All that is fine. I would like to know what are the files and libraries that come as a part of this SDK. Also does it come when I install the OS or when I install editors like Visual studio? Sometimes I see links to windows SDK separately as such. Is it same as the one that I get when installing Visual Studio or has something more than that.

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• Issue in configuring JPA with Spring 3 in Jboss 4.2.2 server.

  - by KVMKReddy

  Hi, I am facing issues in configuring JPA with Spring 3 in JBoss 4.2.2 server. Please find the below file of persistence.xml. <?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="TestPU"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jta-data-source>java:/TestDS</jta-data-source> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect"/> <property name="hibernate.show_sql" value="true"/> </properties> </persistence-unit> </persistence> My spring-beans.xml is as below <bean id="MyAdvise" class=".......Aspect"> <property name="persister"> <bean id="dbPersister" class="..............DataBasePersister"> </bean> </property> </bean> <bean id="localContainerEntityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <property name="showSql" value="true"/> <property name="database" value="ORACLE"/> </bean> </property> <property name="jpaProperties"> <props> <prop key="hibernate.transaction.manager_lookup_class">org.hibernate.transaction.JBossTransactionManagerLookup</prop> </props> </property> </bean> <bean id="myTxManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="localContainerEntityManagerFactory"/> </bean> <tx:annotation-driven transaction-manager="myTxManager" /> My persister bean is as follows. public class DataBasePersister implements IPersister { private static Logger log = Logger.getLogger(DataBasePersister.class); // The Entity Manager @PersistenceContext protected EntityManager entityManager; @Transactional(readOnly = false) public void persist(Object data) { log.info("IN persist() call. Is the data can castable to MethodStats -->:"+(data instanceof MethodStats)); log.info("Entity Manager instance -->:"+(entityManager)); ---------------------- ---------------------- ---------------------- } } I am getting the following exception when the spring container creating my persister bean org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is java.lang.IllegalStateException: JTA EntityManager cannot access a transactions at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:382) at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371) 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:585) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:166) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy147.getTransaction(Unknown Source) at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:335) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at $Proxy141.persist(Unknown Source) at com.adp.sbs.aop.aspectj.SBSMethodStatsCollectorAspect.doAround(SBSMethodStatsCollectorAspect.java:63) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621) at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610) at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:65) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161) at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:621) at com.adp.sbs.aop.test.TestMethodLevelAnnotationStats$$EnhancerByCGLIB$$efbc78a8.MethodWithOneParamsAndReturnTypeAsString(<generated>) at com.adp.sbs.aop.test.SimpleTestServlet.testMethodAnnotations(SimpleTestServlet.java:46) at com.adp.sbs.aop.test.SimpleTestServlet.doPost(SimpleTestServlet.java:40) at com.adp.sbs.aop.test.SimpleTestServlet.doGet(SimpleTestServlet.java:33) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) 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:230) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446) at java.lang.Thread.run(Thread.java:595) Caused by: java.lang.IllegalStateException: JTA EntityManager cannot access a transactions at org.hibernate.ejb.AbstractEntityManagerImpl.getTransaction(AbstractEntityManagerImpl.java:316) at org.springframework.orm.jpa.DefaultJpaDialect.beginTransaction(DefaultJpaDialect.java:70) at org.springframework.orm.jpa.vendor.HibernateJpaDialect.beginTransaction(HibernateJpaDialect.java:57) at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:332) Can you somebody please suggest me how to resolve this.

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• Have the default security settings changed in Windows 7 that would affect IPrincipal.IsInRole?

  - by adrianbanks

  We use NTLM auth in our application to determine whether a user can perform certain operations. We use the IPrincipal of their current Windows login (in WinForms applications), calling IsInRole to check for specific group memberships. To check that a user is a local administrator on the machine, we use: AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal); ... bool allowed = Thread.CurrentPrincipal.IsInRole(@"Builtin\Administrators") This works if the current user is the Administrator user, or is another user that is a member of the Builtin\Administrators group. In our testing on Windows 7, we have found that this no longer works as expected. The Administrator user still works fine, but any other user that is a member of the Builtin\Administrators group returns false for the IsInRole call. What could be causing this difference? I have a gut feeling that a default setting has changed somewhere (possible in gpedit), but cannot find anything that looks like the culprit.

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• Sending SMTP e-mail at a high rate in .NET

  - by Martin Liversage

  I have a .NET service that processes a queue on a background thread and from the items in the queue sends out a large number of small e-mail messages at a very high rate (say 100 messages per second if that is even possible). Currently, I use SmtpClient.Send() but I'm afraid that it may hamper performance. Each call to Send() goes through a full cycle of opening the socket, performing the SMTP conversation (HELO, MAIL FROM, RCPT TO, DATA) and closing the socket. In pseudo code: for each message { open socket send HELO send MAIL FROM send RCPT TO send DATA close socket } I would think that the following pseudo code would be more optimal: open socket send HELO for each message { send MAIL FROM send RCPT TO send DATA } send QUIT close socket Should I be concerned about the performance of SmtpClient.Send() when sending e-mail at a high rate? What are my options for optimizing the performance?

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• Can I create support multiple database transactions on a single connection?

  - by draezal

  I have created a HyperSQL Database. I was just wondering whether I could run multiple transactions on a single connection. I didn't want to spawn a new connection for each transaction due to the overhead associated with this. Looking at some similar questions the suggestion appeared to be to create a pool of database connections and then block waiting for one to become available. This is a workable, but not desirable solution. Background Info (if this is relevant to the answer). My application will create a new thread when some request comes in. This request will require a database transaction. Then some not insignificant time later this transaction will be committed. Any advice appreciated :)

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• How can I debug an unhandled exception in code called from a BackgroundWorker?

  - by SkippyFire

  I am running some import code asynchronously from a simple WinForms app using a BackgroundWorker object and its DoAsync() method. I had a problem where I didn't know that exceptions were being thrown and the thread was prematurely dying. I eventually discovered this, and now know when an exception is thrown after reading Unhandled exceptions in BackgroundWorker. However, I still have a problem while debugging. How do I debug this code? I guess I could run it in a test app that doesn't use a BackgrounWorker, but is there a way to debug this as is? If I step through the code that actually throws the exception, I just get kicked out the step-through when the exception occurs. Re-throwing the exception from the RunWorkerCompletedEventHandler naturally doesn't help much either. Any ideas!? Thanks in advance!

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• XSD - problem with schema generation

  - by lm

  Hello I'm tring to generate schema for some type from assembly with xsd.exe here is command line : xsd.exe TestAssemby.dll /t:TestType Here is error I got Error: There was an error processing 'TestAssemby.dll'. - Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information I copied referenced dll into folder where is located according to http://social.msdn.microsoft.com/Forums/en/xmlandnetfx/thread/308e4f3a-e1c3-43f5-b7a6-a82f1395997d but still get the same error I have questions : 1) What can be possible reasons of such error ? 2) How should be used LoaderExceptions property ? ( example will be very helpful) Thanks in advance

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• audio stream sampling rate in linux

  - by farhan

  Im trying read and store samples from an audio microphone in linux using C/C++. Using PCM ioctls i setup the device to have a certain sampling rate say 10Khz using the SOUND_PCM_WRITE_RATE ioctl etc. The device gets setup correctly and im able to read back from the device after setup using the "read". int got = read(itsFd, b.getDataPtr(), b.sizeBytes()); The problem i have is that after setting the appropriate sampling rate i have a thread that continuously reads from /dev/dsp1 and stores these samples, but the number of samples that i get for 1 second of recording are way off the sampling rate and always orders of magnitude more than the set sampling rate. Any ideas where to begin on figuring out what might be the problem?

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• Conceptual question about NSAutoreleasePools

  - by ryyst

  In my Cocoa program, wouldn't a really simple way of dealing with autoreleased objects be to just create a timer object inside the app delegate that calls the following method e.g. every 10 seconds: if (pool) { // Release & drain the current pool to free the memory. [pool release]; } // Create a new pool. pool = [[NSAutoreleasePool alloc] init]; The only problems I can imagine are: 1) If the above code runs in a separate thread, an object might get autoreleased between the release call to the old pool and the creation of the new pool - that seems highly unlikely though. 2) It's obviously not that efficient, because the pool might get released if there's nothing in it. Likewise, in the 10 second gap, many many objects might be autoreleased, causing the pool to grow a lot. Still, the above solution seems pretty suitable to small and simple projects. Why doesn't anybody use it? What's the best practice of using NSAutoreleasePools?

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• Finding Errant Output to System.out in Large Java Program

  - by SvrGuy

  Hi, We have a large java code base [~1 M Lines]. Buried (somewhere) in the code base is some old debug output to System.out that we want to remove (its cluttering things up). The problem is: out code base is so large that we can't easily find where the output is coming from. What we want is a way to see where System.out.println is getting called from (like a stack trace from an exception or some such). Its not suitable to debugging -- the errant output is coming from some errant thread somewhere etc. Any ideas on how to track the source of this errant output down? PS: 99.99% of calls to System.out are legit, and we have thousands of them, so simply searching the code base for System.out calls is not a solution!

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• Weblogic / EjbGen: worker manager configuration.

  - by Guillaume

  I want to declare a worker manager to perform some work in managed thread. Weblogic documentation tells that we can declare a global worker manager using the admin console or declare it in an ejb-jar.xml config file. I want to use the second option. But my ejb-jar.xml is generated by the ejbgen tool. There is no tag in ejbgen that would allow me to declare a worker manager. So how should I create a local worker manager declaration ?

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• StringBuilder/StringBuffer vs. "+" Operator

  - by matt.seil

  I'm reading "Better, Faster, Lighter Java" (by Bruce Tate and Justin Gehtland) and am familiar with the readability requirements in agile type teams, such as what Robert Martin discusses in his clean coding books. On the team I'm on now, I've been told explicitly not to use the "+" operator because it creates extra (and unnecessary) string objects during runtime. But this article: http://www.ibm.com/developerworks/java/library/j-jtp01274.html Written back in '04 talks about how object allocation is about 10 machine instructions. (essentially free) It also talks about how the GC also helps to reduce costs in this environment. What is the actual performance tradeoffs between using "+," "StringBuilder," or "StringBuffer?" (In my case it is StringBuffer only as we are limited to Java 1.4.2.) StringBuffer to me results in ugly, less readable code, as a couple of examples in Tate's book demonstrates. And StringBuffer is thread-synchronized which seems to have its own costs that outweigh the "danger" in using the "+" operator. Thoughts/Opinions?

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• Django Admin: Many-to-Many listbox doesn't show up with a through parameter

  - by NP

  Hi All, I have the following models: class Message(models.Model): date = models.DateTimeField() user = models.ForeignKey(User) thread = models.ForeignKey('self', blank=True, null=True) ... class Forum(models.Model): name = models.CharField(max_length=24) messages = models.ManyToManyField(Message, through="Message_forum", blank=True, null=True) ... class Message_forum(models.Model): message = models.ForeignKey(Message) forum = models.ForeignKey(Forum) status = models.IntegerField() position = models.IntegerField(blank=True, null=True) tags = models.ManyToManyField(Tag, blank=True, null=True) In the admin site, when I go to add/change a forum, I don't see the messages listbox as you'd expect. However, it shows up if I remove the 'through' parameter in the ManyToManyField declaration. What's up with that? I've registered all three models (plus Tag) to the admin site in admin.py. TIA

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• [C#] foreach loop corrent index

  - by Eyla

  Is there anyway to know the current run of a foreach without have to: Int32 i; foreach i++; or is that the best option i got?? Also, how can i know the maximum number of items on that loop?? What i am trying to do is update a progressbar during a foreach loop on my form Thanks This is what i got foreach (FileInfo file in DirectoryFiles) { if ((file.Attributes & FileAttributes.Hidden) == FileAttributes.Hidden || (file.Attributes & FileAttributes.System) == FileAttributes.System) continue; backgroundWorkerLoadDir.ReportProgress(i, file.Name); System.Threading.Thread.Sleep(10); }

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• What is the point/purpose of Ruby EventMachine, Python Twisted, or JavaScript Node.js?

  - by CCw

  I don't understand what problem these frameworks solve. Are they replacements for a HTTP server like Apache HTTPD, Tomcat, Mongrel, etc? Or are they more? Why might I use them... some real world examples? I've seen endless examples of chat rooms and broadcast services, but don't see how this is any different than, for instance, setting up a Java program to open sockets and dispatch a thread for each request. I think I understand the non-blocking I/O, but I don't understand how that is any different than a multi-threaded web server.

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• producing a typewriter-like effect

  - by Tony Ennis

  Android newb here. Please use small words :-) I'd like to simulate typewriter output on my Android. The output being displayed is generated by a game and is somewhat freeform. The effect I want to see individual characters appear at a rate of about 6 characters a second. When a 'carriage return' is seen, I'd like to insert a delay then resume typing on the left. What are some suggestions on views? Would the view of choice for this be a TextView? Even that seems like overkill for this read-only coarsely scrolling output. I saw something on this thread about an AsyncTask. That looks useful. Perhaps my game will write to some manner of buffer, and a subclass of AsyncTask will pull characters out every .15 seconds or so, add them to the TextView, then invalidate() the TextView? Sound like a plan?

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• Modal dialog blocks wcf callback

  - by Bjarne

  I am working on an application that relies strongly on a wcf request/callback pattern. That is, it uses a service which exposes a number of methods, and for each method there is a callback on which the result is returned. In the client, I wish to open a modal dialog, make a request on the server and then wait for the result on the callback. But I never get a callback since the UI thread is blocked by the modal dialog. Has anyone worked with a similar pattern? I would hate to have more threads in the client, and I also don't like the idea of 'simulating' a modal dialog.

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• c# ref keyword... Am i passing my value correctly?

  - by Pandiya Chendur

  Is this a valid value for this c# class default constructor, public class SMSCOMMS { public SMSCOMMS(ref string COMMPORT) { SMSPort = new SerialPort(); SMSPort.PortName = COMMPORT; SMSPort.BaudRate = 9600; SMSPort.Parity = Parity.None; SMSPort.DataBits = 8; SMSPort.StopBits = StopBits.One; SMSPort.Handshake = Handshake.RequestToSend; SMSPort.DtrEnable = true; SMSPort.RtsEnable = true; SMSPort.NewLine = System.Environment.NewLine; ReadThread = new Thread( new System.Threading.ThreadStart(ReadPort)); } and i am passing this value, SMSCOMMS SMSEngine = new SMSCOMMS("COM6"); but it doesn't seem to take "COM6" as a valid ref string... Any suggestion..

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