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• Silverlight performance with many loaded controls

  - by gius

  I have a SL application with many DataGrids (from Silverlight Toolkit), each on its own view. If several DataGrids are opened, changing between views (TabItems, for example) takes a long time (few seconds) and it freezes the whole application (UI thread). The more DataGrids are loaded, the longer the change takes. These DataGrids that slow the UI chanage might be on other places in the app and not even visible at that moment. But once they are opened (and loaded with data), they slow showing other DataGrids. Note that DataGrids are NOT disposed and then recreated again, they still remain in memory, only their parent control is being hidden and visible again. I have profiled the application. It shows that agcore.dll's SetValue function is the bottleneck. Unfortunately, debug symbols are not available for this Silverlight native library responsible for drawing. The problem is not in the DataGrid control - I tried to replace it with XCeed's grid and the performance when changing views is even worse. Do you have any idea how to solve this problem? Why more opened controls slow down other controls? I have created a sample that shows this issue: http://cenud.cz/PerfTest.zip UPDATE: Using VS11 profiler on the sample provided suggests that the problem could be in MeasureOverride being called many times (for each DataGridCell, I guess). But still, why is it slower as more controls are loaded elsewhere? Is there a way to improve the performance?

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• Unable to get data from a WCF client

  - by Scott

  I am developing a DLL that will provide sychronized time stamps to multiple applications running on the same machine. The timestamps are altered in a thread that uses a high performance timer and a scalar to provide the appearance of moving faster than real-time. For obvious reasons I want only 1 instance of this time library, and I thought I could use WCF for the other processes to connect to this and poll for timestamps whenever they want. When I connect however I never get a valid time stamp, just an empty DateTime. I should point out that the library does work. The original implementation was a single DLL that each application incorporated and each one was synced using windows messages. I'm fairly sure it has something to do with how I'm setting up the WCF stuff, to which I am still pretty new. Here are the contract definitions: public interface ITimerCallbacks { [OperationContract(IsOneWay = true)] void TimerElapsed(String id); } [ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(ITimerCallbacks))] public interface ISimTime { [OperationContract] DateTime GetTime(); } Here is my class definition: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)] public class SimTimeServer: ISimTime The host setup: // set up WCF interprocess comms host = new ServiceHost(typeof(SimTimeServer), new Uri[] { new Uri("net.pipe://localhost") }); host.AddServiceEndpoint(typeof(ISimTime), new NetNamedPipeBinding(), "SimTime"); host.Open(); and the implementation of the interface function server-side: public DateTime GetTime() { if (ThreadMutex.WaitOne(20)) { RetTime = CurrentTime; ThreadMutex.ReleaseMutex(); } return RetTime; } Lastly the client-side implementation: Callbacks myCallbacks = new Callbacks(); DuplexChannelFactory pipeFactory = new DuplexChannelFactory(myCallbacks, new NetNamedPipeBinding(), new EndpointAddress("net.pipe://localhost/SimTime")); ISimTime pipeProxy = pipeFactory.CreateChannel(); while (true) { string str = Console.ReadLine(); if (str.ToLower().Contains("get")) Console.WriteLine(pipeProxy.GetTime().ToString()); else if (str.ToLower().Contains("exit")) break; }

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• Checking if a console application is still running using the Process class

  - by Ced

  I'm making an application that will monitor the state of another process and restart it when it stops responding, exits, or throws an error. However, I'm having trouble to make it reliably check if the process (Being a C++ Console window) has stopped responding. My code looks like this: public void monitorserver() { while (true) { server.StartInfo = new ProcessStartInfo(textbox_srcdsexe.Text, startstring); server.Start(); log("server started"); log("Monitor started."); while (server.Responding) { if (server.HasExited) { log("server exitted, Restarting."); break; } log("server is running: " + server.Responding.ToString()); Thread.Sleep(1000); } log("Server stopped responding, terminating.."); try { server.Kill(); } catch (Exception) { } } } The application I'm monitoring is Valve's Source Dedicated Server, running Garry's Mod, and I'm over stressing the physics engine to simulate it stopping responding. However, this never triggers the process class recognizing it as 'stopped responding'. I know there are ways to directly query the source server using their own protocol, but i'd like to keep it simple and universal (So that i can maybe use it for different applications in the future). Any help appreciated

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• How important is the programming language when you choose a new job?

  - by Luhmann

  We are currently hiring at the company where I work, and here the codebase is in VB.Net. We are worried that we miss out on a lot of brilliant programmers, who would never ever consider working with VB.Net. My own background is Java and C#, and I was somewhat sceptical as to whether it would work out with VB, as - to be honest - i didn't care much for VB. After a month or so, I was completely fluent in VB, and a few months later i discovered to my surprise, that I actually like VB. I still code my free time projects in C# and Boo though. So my question is firstly, how important is language for you, when you choose a new programming job? Lets say if its a great company, salary is good, and generally an attractive work-place. Would you say no to the perfect job, if the language wasn't your preferred dialect? VB or C# is one thing, but how about Java or C# etc. Secondly if the best developers won't join your company because of your language or platform, would you consider changing, to get the right people? (This is not a language bashing thread, so please no religious language wars) NB: This is Community Wiki

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• Why does instanceof seem to work in a static generic function sometimes?

  - by michael

  Greetings. This is my first post in this site. I thought that because of type erasure, one could not expect the following code to compile, and indeed, it did not compile on an earlier version of Eclipse. My understanding was that instanceof was a run-time operator and could not know about the generic type which would be, by run-time, compiled away: public static <E extends Comparable<? super E>> void SampleForQuestion(E e) { if ( !(e instanceof String) ) System.out.println("I am not a String"); else System.out.println("I am a String"); } However, I was surprised to see that one of your threads actually included some code like this in an answer, and my latest Eclipse (Galileo on Windows with JVM 1.6 rev 20) is perfectly happy with it -- and it works, too. (I did notice that someone said it worked on Eclipse but not in another IDE/JDK in that thread, but don't remember the specifics.) Can someone explain why it works, and more importantly, because I have to guide my students, whether it should be expected to work in the future. Thank you. (I hope the code formatting comes through correctly - it looks indented correctly from my perspective and there are no tabs.)

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• ReaderWriterLockSlim and Pulse/Wait

  - by Jono

  Is there an equivalent of Monitor.Pulse and Monitor.Wait that I can use in conjunction with a ReaderWriterLockSlim? I have a class where I've encapsulated multi-threaded access to an underlying queue. To enqueue something, I acquire a lock that protects the underlying queue (and a couple of other objects) then add the item and Monitor.Pulse the locked object to signal that something was added to the queue. public void Enqueue(ITask task) { lock (mutex) { underlying.Enqueue(task); Monitor.Pulse(mutex); } } On the other end of the queue, I have a single background thread that continuously processes messages as they arrive on the queue. It uses Monitor.Wait when there are no items in the queue, to avoid unnecessary polling. (I consider this to be good design, but any flames (within reason) are welcome if they help me learn otherwise.) private void DequeueForProcessing(object state) { while (true) { ITask task; lock (mutex) { while (underlying.Count == 0) { Monitor.Wait(mutex); } task = underlying.Dequeue(); } Process(task); } } As more operations are added to this class (requiring read-only access to the lock protected underlying), someone suggested using ReaderWriterLockSlim. I've never used the class before, and assuming it can offer some performance benefit, I'm not against it, but only if I can keep the Pulse/Wait design.

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• What should be taught in a "Fundamentals of programming" course at university?

  - by Dervin Thunk

  I have started a new question (see here), because I think the topic is of importance in a more general form. The question is now: If you were a professor at a Computer Science Dept. in some university, what would make it into your course? This is a programming course, second term, first year computer science/computer engineering. Remember you have a limited amount of time, and students are of different levels of competence, and some may be scientists, but some will also go on to be programmers in companies of different kinds. You have to cater to all. Bonus: What language? (Although see this question for my current thoughts about this...) Maybe you want to attach a course outline from some university? See here for an even more general question about this. Answer: I can't really summarize this post... I guess it was too subjective. However, it looks like we have to cover the history of computing up to a certain extent, computer architecture (memory, registers, whatever), C, and finally some basic algos and data structures in a problem solving fashion. This will be the bare bones of the course. Thanks all. I will accept the most voted up answer to close the thread, as it should be done.

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• using a While loop to control the value of a keyframe in a timeline in Javafx

  - by dragoknight

  i want to create an animation where the ball will move in one of the 4 sectors of a circle randomly.this will happen 5 times.so,i create a while loop(i<5) and call the random function.i then create an if loop and attach some x and y values according to the random fn value.i then create an timeline object inside the while loop and in the key frame value,i use these x and y values.but when i run the program,what happens is that all the values are being created(x and y values seen through println) but only the last x and y value(for i=5)is being rendered in the screen.the animations for the previous values(1<=i<=4)are not being rendered.Please advise where have i gone wrong? public function run(args:String[]) { var i=0; while(i<5) { var z=gety(); println(z); // var relativeTime:Duration=0s; if(z==1) {xbind=120; ybind=80; } else if(z==2) {xbind=120; ybind=120; } else if(z==3) { xbind=80; ybind=120; } else if(z==4) { xbind=80; ybind=80; } var t:Timeline=Timeline{ //time: bind pos with inverse; repeatCount: Timeline.INDEFINITE autoReverse: true keyFrames: [ KeyFrame{ time: 0s values: [ x => 100.0,y => 100.0]}, KeyFrame{time: 2s values:[x => xbind tween Interpolator.LINEAR, y => ybind tween Interpolator.LINEAR,] }, ] }//end timeline i++; t.play(); Thread.sleep(2000); }//end while }

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• What limits scaling in this simple OpenMP program?

  - by Douglas B. Staple

  I'm trying to understand limits to parallelization on a 48-core system (4xAMD Opteron 6348, 2.8 Ghz, 12 cores per CPU). I wrote this tiny OpenMP code to test the speedup in what I thought would be the best possible situation (the task is embarrassingly parallel): // Compile with: gcc scaling.c -std=c99 -fopenmp -O3 #include <stdio.h> #include <stdint.h> int main(){ const uint64_t umin=1; const uint64_t umax=10000000000LL; double sum=0.; #pragma omp parallel for reduction(+:sum) for(uint64_t u=umin; u<umax; u++) sum+=1./u/u; printf("%e\n", sum); } I was surprised to find that the scaling is highly nonlinear. It takes about 2.9s for the code to run with 48 threads, 3.1s with 36 threads, 3.7s with 24 threads, 4.9s with 12 threads, and 57s for the code to run with 1 thread. Unfortunately I have to say that there is one process running on the computer using 100% of one core, so that might be affecting it. It's not my process, so I can't end it to test the difference, but somehow I doubt that's making the difference between a 19~20x speedup and the ideal 48x speedup. To make sure it wasn't an OpenMP issue, I ran two copies of the program at the same time with 24 threads each (one with umin=1, umax=5000000000, and the other with umin=5000000000, umax=10000000000). In that case both copies of the program finish after 2.9s, so it's exactly the same as running 48 threads with a single instance of the program. What's preventing linear scaling with this simple program?

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• Creating PowerShell Automatic Variables from C#

  - by Uros Calakovic

  I trying to make automatic variables available to Excel VBA (like ActiveSheet or ActiveCell) also available to PowerShell as 'automatic variables'. PowerShell engine is hosted in an Excel VSTO add-in and Excel.Application is available to it as Globals.ThisAddin.Application. I found this thread here on StackOverflow and started created PSVariable derived classes like: public class ActiveCell : PSVariable { public ActiveCell(string name) : base(name) { } public override object Value { get { return Globals.ThisAddIn.Application.ActiveCell; } } } public class ActiveSheet : PSVariable { public ActiveSheet(string name) : base(name) { } public override object Value { get { return Globals.ThisAddIn.Application.ActiveSheet; } } } and adding their instances to the current POwerShell session: runspace.SessionStateProxy.PSVariable.Set(new ActiveCell("ActiveCell")); runspace.SessionStateProxy.PSVariable.Set(new ActiveSheet("ActiveSheet")); This works and I am able to use those variables from PowerShell as $ActiveCell and $ActiveSheet (their value change as Excel active sheet or cell change). Then I read PSVariable documentation here and saw this: "There is no established scenario for deriving from this class. To programmatically create a shell variable, create an instance of this class and set it by using the PSVariableIntrinsics class." As I was deriving from PSVariable, I tried to use what was suggested: PSVariable activeCell = new PSVariable("ActiveCell"); activeCell.Value = Globals.ThisAddIn.Application.ActiveCell; runspace.SessionStateProxy.PSVariable.Set(activeCell); Using this, $ActiveCell appears in my PowerShell session, but its value doesn't change as I change the active cell in Excel. Is the above comment from PSVariable documentation something I should worry about, or I can continue creating PSVariable derived classes? Is there another way of making Excel globals available to PowerShell?

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• Can an application affect TCP retransmits

  - by sipwiz

  I'm troubleshooting some communications issues and in the network traces I am occasionally coming across TCP sequence errors. One example I've got is: Server to Client: Seq=3174, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3224, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3274, Len=10 Client to Server: Ack=3224, SLE=3274, SRE=3284 Packets 4 & 5 are recorded in the trace (which is from a router in between the client and server) at almost exactly the same time so they most likely crossed in transit. The TCP session has got out of sync with the client missing the last two transmissions from the server. Those two packets should have been retransmitted but they weren't, the next log in the trace is a RST packet from the Client 24 seconds after packet 6. My question is related to what could be responsible for the failure to retransmit the server data from packets 3 & 5? I would assume that the retransmit would be at the operating system level but is there anyway the application could influence it and stop it being sent? A thread blocking or put to sleep or something like that?

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• committing to a branch that's not checked out

  - by intuited

  I'm using git to version my home directories on a couple different machines. I'd like for them to each use separate branches and both pull from a common branch. So most commits should be made to that common branch, unless something specific to that machine is being committed, in which case the commit should go to the checked out, machine-specific branch. Switching branches is clearly not a very good option in this case. It's mentioned in this post that what I want to do is impossible, but I found that answer to be rather blunt and to perhaps not take into account the possibility of using the plumbing commands. Unfortunately I don't have enough reputation to comment on that thread. I rather suspect that there is some way to do this and am hoping to save myself an hour or few of questing for the answer by just asking you good folk. So is it possible to commit to a different branch without checking that branch out first? Ideally I'd like to use the index in the same way that git commit normally does.

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• How to efficiently store and update binary data in Mongodb?

  - by Rocketman

  I am storing a large binary array within a document. I wish to continually add bytes to this array and sometimes change the value of existing bytes. I was looking for some $append_bytes and $replace_bytes type of modifiers but it appears that the best I can do is $push for arrays. It seems like this would be doable by performing seek-write type operations if I had access somehow to the underlying bson on disk, but it does not appear to me that there is anyway to do this in mongodb (and probably for good reason). If I were instead to just query this binary array, edit or add to it, and then update the document by rewriting the entire field, how costly will this be? Each binary array will be on the order of 1-2MB, and updates occur once every 5 minutes and across 1000s of documents. Worse, yet there is no easy way to spread these out (in time) and they will usually be happening close to one another on the 5 minute intervals. Does anyone have a good feel for how disastrous this will be? Seems like it would be problematic. An alternative would be to store this binary data as separate files on disk, implement a thread pool to efficiently manipulate the files on disk, and reference the filename from my mongodb document. (I'm using python and pymongo so I was looking at pytables). I'd prefer to avoid this though if possible. Is there any other alternative that I am overlooking here? Thanks in advnace.

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• Why does GetWindowThreadProcessId return 0 when called from a service

  - by Marve

  When using the following class in a console application, and having at least one instance of Notepad running, GetWindowThreadProcessId correctly returns a non-zero thread id. However, if the same code is included in a Windows Service, GetWindowThreadProcessId always returns 0 and no exceptions are thrown. Changing the user the service launches under to be the same as the one running the console application didn't alter the result. What causes GetWindowThreadProcessId to return 0 even if it is provided with a valid hwnd? And why does it function differently in the console application and the service? Note: I am running Windows 7 32-bit and targeting .NET 3.5. public class TestClass { [DllImport("user32.dll")] static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr ProcessId); public void AttachToNotepad() { var processesToAttachTo = Process.GetProcessesByName("Notepad") foreach (var process in processesToAttachTo) { var threadID = GetWindowThreadProcessId(process.MainWindowHandle, IntPtr.Zero); .... } } } Console Code: class Program { static void Main(string[] args) { var testClass = new TestClass(); testClass.AttachToNotepad(); } } Service Code: public class TestService : ServiceBase { private TestClass testClass = new TestClass(); static void Main() { ServiceBase.Run(new TestService()); } protected override void OnStart(string[] args) { testClass.AttachToNotepad(); base.OnStart(args); } protected override void OnStop() { ... } }

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• Dependency Injection into your Singleton

  - by Langali

  I have a singleton that has a spring injected Dao (simplified below): public class MyService<T> implements Service<T> { private final Map<String, T> objects; private static MyService instance; MyDao myDao; public void set MyDao(MyDao myDao) { this. myDao = myDao; } private MyService() { this.objects = Collections.synchronizedMap(new HashMap<String, T>()); // start a background thread that runs for ever } public static synchronized MyService getInstance() { if(instance == null) { instance = new MyService(); } return instance; } public void doSomething() { myDao.persist(objects); } } My spring config will probably look like this: <bean id="service" class="MyService" factory-method="getInstance"/> But this will instantiate the MyService during startup. Is there a programmatic way to do a dependency injection of MyDao into MyService, but not have spring manage the MyService? Basically I want to be able to do this from my code: MyService.getInstance().doSomething(); while having spring inject the MyDao for me.

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• Strange problem with simple multithreading program in Java

  - by Elizabeth

  Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

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• Pump Messages During Long Operations + C#

  - by Newbie

  Hi I have a web service that is doing huge computation and is taking more than a minute. I have generated the proxy file of the web service and then from my client end I am using the dll(of course I generated the proxy dll). My client side code is TimeSeries3D t = new TimeSeries3D(); int portfolioId = 4387919; string[] str = new string[2]; str[0] = "MKT_CAP"; DateRange dr = new DateRange(); dr.mStartDate = DateTime.Today; dr.mEndDate = DateTime.Today; Service1 sc = new Service1(); t = sc.GetAttributesForPortfolio(portfolioId, true, str, dr); But since it is taking to much time for the server to compute, after 1 minute I am receiving an error message The CLR has been unable to transition from COM context 0x33caf30 to COM context 0x33cb0a0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Kindly guide me what to do? Thanks

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• pthread_exit and/or pthread_join causing Abort and SegFaults.

  - by MJewkes

  The following code is a simple thread game, that switches between threads causing the timer to decrease. It works fine for 3 threads, causes and Abort(core dumped) for 4 threads, and causes a seg fault for 5 or more threads. Anyone have any idea why this might be happening? #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <errno.h> #include <assert.h> int volatile num_of_threads; int volatile time_per_round; int volatile time_left; int volatile turn_id; int volatile thread_running; int volatile can_check; void * player (void * id_in){ int id= (int)id_in; while(1){ if(can_check){ if (time_left<=0){ break; } can_check=0; if(thread_running){ if(turn_id==id-1){ turn_id=random()%num_of_threads; time_left--; } } can_check=1; } } pthread_exit(NULL); } int main(int argc, char *args[]){ int i; int buffer; pthread_t * threads =(pthread_t *)malloc(num_of_threads*sizeof(pthread_t)); thread_running=0; num_of_threads=atoi(args[1]); can_check=0; time_per_round = atoi(args[2]); time_left=time_per_round; srandom(time(NULL)); //Create Threads for (i=0;i<num_of_threads;i++){ do{ buffer=pthread_create(&threads[i],NULL,player,(void *)(i+1)); }while(buffer == EAGAIN); } can_check=1; time_left=time_per_round; turn_id=random()%num_of_threads; thread_running=1; for (i=0;i<num_of_threads;i++){ assert(!pthread_join(threads[i], NULL)); } return 0; }

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• How to use Comparator in Java to sort

  - by Dan

  I learned how to use the comparable but I'm having difficulty with the Comparator. I am having a error in my code: Exception in thread "main" java.lang.ClassCastException: New.People cannot be cast to java.lang.Comparable at java.util.Arrays.mergeSort(Unknown Source) at java.util.Arrays.sort(Unknown Source) at java.util.Collections.sort(Unknown Source) at New.TestPeople.main(TestPeople.java:18) Here is my code: import java.util.Comparator; public class People implements Comparator{ private int id; private String info; private double price; public People(int newid, String newinfo, double newprice){ setid(newid); setinfo(newinfo); setprice(newprice); } public int getid() { return id; } public void setid(int id) { this.id = id; } public String getinfo() { return info; } public void setinfo(String info) { this.info = info; } public double getprice() { return price; } public void setprice(double price) { this.price = price; } public int compare(Object obj1, Object obj2) { Integer p1 = ((People)obj1).getid(); Integer p2 = ((People)obj2).getid(); if (p1 p2 ){ return 1; } else if (p1 < p2){ return -1; } else return 0; } } import java.util.ArrayList; import java.util.Collections; public class TestPeople { public static void main(String[] args) { ArrayList peps = new ArrayList(); peps.add(new People(123, "M", 14.25)); peps.add(new People(234, "M", 6.21)); peps.add(new People(362, "F", 9.23)); peps.add(new People(111, "M", 65.99)); peps.add(new People(535, "F", 9.23)); Collections.sort(peps); for(int i=0;i I believe it has to do something with the casting in the compare method but I was playing around with it and still could not find the solution

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• Filp route value in asp.net mvc routes

  - by Herman

  Hi all, I am new to asp.net mvc, so please bear with me. We have the following route dictionary setup. routes.MapRoute( "Default", // Route name "{language}/{controller}/{action}/{id}", // URL with parameters new { language = "en", controller = "Home", action = "Index", id = "" } // Parameter defaults ); for any given page in our app, we to render a link to the a french version of the same page. For example, the page: http://www.example.com/en/home should have link on that page that points to http://www.example.com/fr/home Now I have the following UrlHelper extension method public static string FilpLanguage(this UrlHelper urlHelper) { var data = urlHelper.RequestContext.RouteData; if (System.Threading.Thread.CurrentThread.CurrentCulture == CultureInfo.GetCultureInfoByIetfLanguageTag("en-CA")) data.Values["language"] = "fr"; else data.Values["language"] = "en"; return urlHelper.RouteUrl(data.Values.Where(item => item.Value != null)); } However, calling FilpLanguage on www.example.com/en/home will return the following URL: www.example.com/en/home?current=[,] Am I missing something here? where did the current parameter come from? Thanks in advance.

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• Issue reading in a cell from Excel with Apache POI

  - by Nick

  I am trying to use Apache POI to read in old (pre-2007 and XLS) Excel files. My program goes to the end of the rows and iterates back up until it finds something that's not either null or empty. Then it iterates back up a few times and grabs those cells. This program works just fine reading in XLSX and XLS files made in Office 2010. I get the following error message: Exception in thread "main" java.lang.NumberFormatException: empty String at sun.misc.FloatingDecimal.readJavaFormatString(Unknown Source) at java.lang.Double.parseDouble(Unknown Source) at the line: num = Double.parseDouble(str); from the code: str = cell.toString(); if (str != "" || str != null) { System.out.println("Cell is a string"); num = Double.parseDouble(str); } else { System.out.println("Cell is numeric."); num = cell.getNumericCellValue(); } where the cell is the last cell in the document that's not empty or null. When I try to print the first cell that's not empty or null, it prints nothing, so I think I'm not accessing it correctly.

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• java bubblesort with acm dialog

  - by qzar

  Hi, the program gives following exception: Exception in thread "main" java.lang.NullPointerException at myclasses.BubbleSort.run(BubbleSort.java:42) at acm.program.Program.runHook(Program.java:1519) at acm.program.Program.startRun(Program.java:1508) at acm.program.Program.start(Program.java:729) at myclasses.BubbleSort.main(BubbleSort.java:49) what is wrong? thank you very much! package myclasses; import acm.program.DialogProgram; public class BubbleSort extends DialogProgram { int[] array; public int[] getArray() { return array; } public void setArray(int[] array) { this.array = array; } void swap(int firstPos, int secondPos) { int temp = array[firstPos]; array[firstPos] = array[secondPos]; array[secondPos] = temp; } public void bubblesort() { int i, j, k; for (i = 1; i < array.length; i++) { j = i; k = array[i]; while (j > 0 && array[j - 1] > k) { array[j] = array[j - 1]; --j; } array[j] = k; } } public void run() { BubbleSort a = new BubbleSort(); a.setArray(new int[] {1, 3, 5, 7, 6, 2}); a.bubblesort(); StringBuffer sb = new StringBuffer(a.array.length * 2); for (int i = 0; i < getArray().length; i++) sb.append(getArray()[i]).append(" "); println(sb); } public static void main(String[] args) { new BubbleSort().start(args); } }

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• Using JavaMail to send a mail containing Unicode characters

  - by NoozNooz42

  I'm successfully sending emails through GMail's SMTP servers using the following piece of code: Properties props = new Properties(); props.put("mail.smtp.host", "smtp.gmail.com"); props.put("mail.smtp.socketFactory.port", "465"); props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory"); props.put("mail.smtp.auth", "true"); props.put("mail.smtp.port", "465"); props.put("mail.smtp.ssl", "true"); props.put("mail.smtp.starttls.enable","true"); props.put("mail.smtp.timeout", "5000"); props.put("mail.smtp.connectiontimeout", "5000"); // Do NOT use Session.getDefaultInstance but Session.getInstance // See: http://forums.sun.com/thread.jspa?threadID=5301696 final Session session = Session.getInstance( props, new javax.mail.Authenticator() { protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication( USER, PWD ); } }); try { final Message message = new MimeMessage(session); message.setFrom( new InternetAddress( USER ) ); message.setRecipients( Message.RecipientType.TO, InternetAddress.parse( TO ) ); message.setSubject( emailSubject ); message.setText( emailContent ); Transport.send(message); emailSent = true; } catch ( final MessagingException e ) { e.printStackTrace(); } where emailContent is a String that does contain Unicode characters (like the euro symbol). When the email arrives (in another GMail account), the euro symbol has been converted to the ASCII '?' question mark. I don't know much about emails: can email use any character encoding? What should I modify in the code above so that an encoding allowing Unicode characters is used?

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• iPhone: Does it ever make sense for an object to retain its delegate?

  - by randombits

  According to the rules of memory management in a non garbage collected world, one is not supposed to retain a the calling object in a delegate. Scenario goes like this: I have a class that inherits from UITableViewController and contains a search bar. I run expensive search operations in a secondary thread. This is all done with an NSOperationQueue and subclasses NSOperation instances. I pass the controller as a delegate that adheres to a callback protocol into the NSOperation. There are edge cases when the application crashes because once an item is selected from the UITableViewController, I dismiss it and thus its retain count goes to 0 and dealloc gets invoked on it. The delegate didn't get to send its message in time as the results are being passed at about the same time the dealloc happens. Should I design this differently? Should I call retain on my controller from the delegate to ensure it exists until the NSOperation itself is dealloc'd? Will this cause a memory leak? Right now if I put a retain on the controller, the crashes goes away. I don't want to leak memory though and need to understand if there are cases where retaining the delegate makes sense. Just to recap. UITableViewController creates an NSOperationQueue and NSOperation that gets embedded into the queue. The UITableViewController passes itself as a delegate to NSOperation. NSOperation calls a method on UITableViewController when it's ready. If I retain the UITableViewController, I guarantee it's there, but I'm not sure if I'm leaking memory. If I only use an assign property, edge cases occur where the UITableViewController gets dealloc'd and objc_msgSend() gets called on an object that doesn't exist in memory and a crash is imminent.

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• Creating a ComboBox with one or more separator items?

  - by Steve

  I'm using Delphi7 and I'd like to have a ComboBox with separator items (Just like in popup menus). I've seen this beautifully implemented in Mozilla Sunbird (I know, it's not Delphi...) the following way: The separator item is a simple gray line drawn in the center of the item If you hover over the separator with the mouse, the selection doesn't appear If the user clicks the separator, it's not selected either AND the combobox doesn't closeup. No. 1 could be implemented using DrawItem. I could live without No. 2 because I have no idea about that. For No. 3 I'm asking for your help. I've figured out that straight after closing up a CBN_CLOSEUP message is sent to the combobox. I thought about hooking the window proc and if CBN_CLOSEUP is sent to a certain combobox then countering it. But I'm unsure if this is the best solution, or maybe there are other, more elegant ways? Whatever the solution is, I'd like to have a standard ComboBox which supports WinXP/Vista/7 theming properly. Thanks! Edit: For a working component please see this thread: Can you help translating this very small C++ component to Delphi?

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