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  • Invoke "internal extern" constructor using reflections

    - by Riz
    Hi, I have following class (as seen through reflector) public class W : IDisposable { public W(string s); public W(string s, byte[] data); // more constructors [MethodImpl(MethodImplOptions.InternalCall)] internal extern W(string s, int i); public static W Func(string s, int i); } I am trying to call "internal extern" constructor or Func using reflections MethodInfo dynMethod = typeof(W).GetMethod("Func", BindingFlags.Static); object[] argVals = new object[] { "hi", 1 }; dynMethod.Invoke(null, argVals); and Type type = typeof(W); Type[] argTypes = new Type[] { typeof(System.String), typeof(System.Int32) }; ConstructorInfo cInfo = type.GetConstructor(BindingFlags.InvokeMethod | BindingFlags.NonPublic, null, argTypes, null); object[] argVals = new object[] { "hi", 1 }; dynMethod.Invoke(null, argVals); unfortunantly both variants rise NullReferenceException when trying to Invoke, so, I must be doing something wrong?

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  • Xpages - Get number of active sessions

    - by Jairo
    How do I get the number of active sessions in Xpage. I'm trying to use managed beans but it just returns a weird string. Here's the simple code: import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; public class SessionCounterListener implements HttpSessionListener { private static int totalActiveSessions; public static int getTotalActiveSessions(){ return totalActiveSessions | 0; } public void sessionCreated(HttpSessionEvent arg0) { totalActiveSessions++; System.out.println("sessionCreated - add one session into counter"); } public void sessionDestroyed(HttpSessionEvent arg0) { totalActiveSessions--; System.out.println("sessionDestroyed - deduct one session from counter"); } } I got this from here. But when I call SessionCounterListener.getTotalActiveSessions(), it only returns a weird string, example com.gs3.beans.SessionCounterListener@46c446c4. Please help me. Thanks a lot!

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  • Seg Fault when using std::string on an embedded Linux platform

    - by Brad
    Hi, I have been working for a couple of days on a problem with my application running on an embedded Arm Linux platform. Unfortunately the platform precludes me from using any of the usual useful tools for finding the exact issue. When the same code is run on the PC running Linux, I get no such error. In the sample below, I can reliably reproduce the problem by uncommenting the string, list or vector lines. Leaving them commented results in the application running to completion. I expect that something is corrupting the heap, but I cannot see what? The program will run for a few seconds before giving a segmentation fault. The code is compiled using a arm-linux cross compiler: arm-linux-g++ -Wall -otest fault.cpp -ldl -lpthread arm-linux-strip test Any ideas greatly appreciated. #include <stdio.h> #include <vector> #include <list> #include <string> using namespace std; ///////////////////////////////////////////////////////////////////////////// class TestSeg { static pthread_mutex_t _logLock; public: TestSeg() { } ~TestSeg() { } static void* TestThread( void *arg ) { int i = 0; while ( i++ < 10000 ) { printf( "%d\n", i ); WriteBad( "Function" ); } pthread_exit( NULL ); } static void WriteBad( const char* sFunction ) { pthread_mutex_lock( &_logLock ); printf( "%s\n", sFunction ); //string sKiller; // <----------------------------------Bad //list<char> killer; // <----------------------------------Bad //vector<char> killer; // <----------------------------------Bad pthread_mutex_unlock( &_logLock ); return; } void RunTest() { int threads = 100; pthread_t _rx_thread[threads]; for ( int i = 0 ; i < threads ; i++ ) { pthread_create( &_rx_thread[i], NULL, TestThread, NULL ); } for ( int i = 0 ; i < threads ; i++ ) { pthread_join( _rx_thread[i], NULL ); } } }; pthread_mutex_t TestSeg::_logLock = PTHREAD_MUTEX_INITIALIZER; int main( int argc, char *argv[] ) { TestSeg seg; seg.RunTest(); pthread_exit( NULL ); }

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  • Why does does my stack overflow error occur after 518669 specifically?

    - by David
    I created a java program to count up toward infinity: class up { public static void up (int n) { System.out.println (n) ; up (n+1) ; } public static void main (String[] arg) { up (1) ; } } i didn't actually expect it to get there but the thing that i noticed that was a bit curious was that it stopped at the same number each time: 518669 what is the significance of this number? (or of this number +1 i suppose). (also as a bit of an aside question, I've been told that the way i format my code is bad [indentation and such] what am i doing that isn't desirable?)

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  • Error Creating RSS Feed XML file - Java

    - by GigaPr
    Hi, i am trying to create an RssFeed using java this is the class i use import com.rssFeed.domain.RSS; import com.rssFeed.domain.RSSItem; import java.io.FileOutputStream; import java.util.Iterator; import javax.xml.stream.XMLEventFactory; import javax.xml.stream.XMLEventWriter; import javax.xml.stream.XMLOutputFactory; import javax.xml.stream.XMLStreamException; import javax.xml.stream.events.Characters; import javax.xml.stream.events.EndElement; import javax.xml.stream.events.StartDocument; import javax.xml.stream.events.StartElement; import javax.xml.stream.events.XMLEvent; public class RssBuilder { private static String XML_BLOCK = "\n"; private static String XML_INDENT = "\t"; public static void BuildRss(RSS rss, String xmlfile) throws Exception { XMLOutputFactory output = XMLOutputFactory.newInstance(); XMLEventWriter writer = output.createXMLEventWriter(new FileOutputStream(xmlfile)); try { XMLEventFactory eventFactory = XMLEventFactory.newInstance(); XMLEvent endSection = eventFactory.createDTD(XML_BLOCK); StartDocument startDocument = eventFactory.createStartDocument(); writer.add(startDocument); writer.add(endSection); StartElement rssStart = eventFactory.createStartElement("", "", "rss"); writer.add(rssStart); writer.add(eventFactory.createAttribute("version", "2.0")); writer.add(endSection); writer.add(eventFactory.createStartElement("", "", "channel")); writer.add(endSection); createNode(writer, "title", rss.getTitle()); createNode(writer, "description", rss.getDescription()); createNode(writer, "link", rss.getLink()); createNode(writer, "dateCreated", rss.getDateCreated().toString()); createNode(writer, "language", rss.getLanguage()); createNode(writer, "pubDate", rss.getPubDate().toString()); createNode(writer, "dateModified", rss.getDateModified().toString()); createNode(writer, "dateModified", rss.getDateModified().toString()); createNode(writer, "pubDate", rss.getPubDate().toString()); createNode(writer, "lastBuildDate", rss.getLastBuildDate().toString()); createNode(writer, "language", rss.getLanguage().toString()); createNode(writer, "rating", rss.getRating().toString()); Iterator<RSSItem> iterator = rss.getRssItems().iterator(); while (iterator.hasNext()) { RSSItem entry = iterator.next(); writer.add(eventFactory.createStartElement("", "", "item")); writer.add(endSection); createNode(writer, "title", entry.getTitle()); createNode(writer, "description", entry.getDescription()); createNode(writer, "link", entry.getLink()); createNode(writer, "dateCreated", entry.getDateCreated().toString()); createNode(writer, "pubDate", entry.getDateModified().toString()); writer.add(eventFactory.createEndElement("", "", "item")); writer.add(endSection); } writer.add(endSection); writer.add(eventFactory.createEndElement("", "", "channel")); writer.add(endSection); writer.add(eventFactory.createEndElement("", "", "rss")); writer.add(endSection); writer.add(eventFactory.createEndDocument()); writer.close(); } catch(Exception e) { writer.close(); } } private static void createNode(XMLEventWriter eventWriter, String name, String value)throws XMLStreamException { XMLEventFactory eventFactory = XMLEventFactory.newInstance(); XMLEvent endSection = eventFactory.createDTD(XML_BLOCK); XMLEvent tabSection = eventFactory.createDTD(XML_INDENT); StartElement sElement = eventFactory.createStartElement("", "", name); eventWriter.add(tabSection); eventWriter.add(sElement); Characters characters = eventFactory.createCharacters(value); eventWriter.add(characters); EndElement eElement = eventFactory.createEndElement("", "", name); eventWriter.add(eElement); eventWriter.add(endSection); } } But i get the following error type Exception report message descriptionThe server encountered an internal error () that prevented it from fulfilling this request. exception org.springframework.web.util.NestedServletException: Request processing failed; nested exception is javax.xml.stream.XMLStreamException: Can not write DOCTYPE declaration (DTD) when not in prolog any more (state 2; start element(s) written) root cause javax.xml.stream.XMLStreamException: Can not write DOCTYPE declaration (DTD) when not in prolog any more (state 2; start element(s) written) what does it mean?

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  • Global keyboard states

    - by Petr Abdulin
    I have following idea about processing keyboard input. We capture input in "main" Game class like this: protected override void Update(GameTime gameTime) { this.CurrentKeyboardState = Keyboard.GetState(); // main :Game class logic here base.Update(gameTime); this.PreviousKeyboardState = this.CurrentKeyboardState; } then, reuse keyboard states (which have internal scope) in all other game components. The reasons behind this are 1) minimize keyboard processing load, and 2) reduce "pollution" of all other classes with similar keyboard state variables. Since I'm quite a noob in both game and XNA development, I would like to know if all of this sounds reasonable.

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  • ubuntu 12.04 install black screen

    - by Tara Scarborough
    When I try to install Ubuntu 12.04 i get the grub 1.99 screen that allows me to select ubuntu install, or try ubuntu with out installing. When i select install ubuntu the screen goes black and i can tell the hard drive is running, but there are no on screen prompts. I looked into this problem and attempted to change a few variables by pressing "e" to edit the ubuntu install boot screen I then changed splash to nospash, quiet to noquiet, and add nomodeset at the end of the line that starts with linux before the "--". This still changes nothing when i press F10 to boot. I have tried removing quiet and splash altogether and adding nomodeset, but still to no avail. I am a little frustrated and don't know what to do. Any help would be greatly appreciated! The system is brand new - no OS: Hardware: Zotac ZBOX ZBOX-ID81-PLUS-U Nettop Computer - Intel Celeron 857 1.20 GHz - 8 GB RAM - 320 GB HDD - Intel Graphics Media Accelerator HD Graphics Card

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  • C# TraceSource class in multithreaded application

    - by matti
    msdn: "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." it contains only instance methods. How should I use it in a way that all activity gets recorder by TextWriterTraceListener to a text file. Is one static member which all threads use (by calling) TraceEvent-method safe. (I've kind of asked this question in http://stackoverflow.com/questions/1901086/how-to-instantiate-c-tracesources-to-log-multithreaded-asp-net-2-0-web-applica, but I cannot just believe if somebody just says it's OK despite the documentation).

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  • Tips on googling for sugar

    - by Mikey
    I have a question up on SO I am a little embarassed I can't just google: http://stackoverflow.com/questions/13734664/groovy-variables-in-method-names-with-double-question-marks The problem is google seems to chuck any terms that are just punctuation, so queries like these: .findBy?? .and?? groovy '??' Are coming out the same as these: findBy and groovy I have had this problem before when I didn't know the name of the elvis operator, and countless other times (probably happened first time I saw an infix '%' mod too if I had to guess). Is there a resource for syntax sugar lookups? Some way to force google or a different search engine to not ignore my funky punctuation?

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  • Alignment of rollover item affected by position of header

    - by Steven
    Hi guys, Got a problem where when you rollover "about us" the rollover appeared to the right of the screen exactly 224 pixels from the edge of the browser (maintained this gap when reducing the size of the browser) I fixed it by changing the .css position of the wrapper (from absolute to static) How ever now as you can see in the example ive done the header is aligning to the left: http://jimbeamracing.com.au/navigationtest.htm wrapper{ margin:0 auto; width:994px; position:static; padding:113px 0 0; } Any help would be much appreciated Regards, Steven

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  • Enabling SSL in MySQL

    - by Bio.X2Y
    I'm running Ubuntu Server 12.04, and I want to enable SSL connections to MySQL. I've generated the following keys/certs files with OpenSSL: ca-cert.pem server-cert.pem server-key.pem I stored these at /etc/mysql, then added added the following lines to /etc/mysql/my.cnf: ssl-ca=/etc/mysql/ca-cert.pem ssl-cert=/etc/mysql/server-cert.pem ssl-key=/etc/mysql/server-key.pem Next, I restarted the server with sudo service restart mysql. However, this doesn't seem to enable SSL. Within a mysql session: mysql> show variables like '%ssl%'; +---------------+----------------------------+ | Variable_name | Value | +---------------+----------------------------+ | have_openssl | DISABLED | | have_ssl | DISABLED | | ssl_ca | /etc/mysql/ca-cert.pem | | ssl_capath | | | ssl_cert | /etc/mysql/server-cert.pem | | ssl_cipher | | | ssl_key | /etc/mysql/server-key.pem | +---------------+----------------------------+ Any ideas what I'm missing? Thanks

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  • When is a PHP project too small for a framework?

    - by Jonathan Nicol
    I'm about to start on a small, static website project: no database or CMS required. Basically, a brochure website. I used the CodeIgniter framework recently to develop a full-blown web application, and I'm wondering if it appropriate to also use CI for smaller, simpler sites. Typically for a static brochure site I would write regular PHP pages with a few includes thrown in to save on repetition (i.e. HTML with a sprinking of PHP), but this time around I'm wondering if my new friend CodeIgniter might be able to streamline the development process. Is it sensible to consider a framework for such a simple project, or is it overkill? I'm worried that I might be the proverbial carpenter whose only tool is a hammer, and sees every problem as a nail!

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  • Run command in command prompt from Ruby application

    - by Julian
    I have a command-line Ruby application that uses Curses to create a GUI. This GUI is absolutely mangled by Windows' command prompt if the command prompt window is too small. The command prompt window can be resized in properties. However, I want to resize it programatically. Running this command in the command prompt (nothing to do with Ruby) will resize the command prompt window to desired variables. mode con:cols=120 lines=40 Can I do this purely in Ruby? Or, failing that (I suspect doing it purely in Ruby may be impossible) can my ruby application actually run that command and 'hit enter', and resize window it's running in?

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  • How to start new browser window in cpecified location whith cpecified size

    - by Pritorian
    Hi all! I create a new instance and trying to resize new instance of browser like this: [System.Runtime.InteropServices.DllImport("user32.dll")] private static extern bool GetWindowInfo(IntPtr hwnd, ref tagWINDOWINFO pwi); [System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)] public struct tagRECT { /// LONG->int public int left; /// LONG->int public int top; /// LONG->int public int right; /// LONG->int public int bottom; } [System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)] public struct tagWINDOWINFO { /// DWORD->unsigned int public uint cbSize; /// RECT->tagRECT public tagRECT rcWindow; /// RECT->tagRECT public tagRECT rcClient; /// DWORD->unsigned int public uint dwStyle; /// DWORD->unsigned int public uint dwExStyle; /// DWORD->unsigned int public uint dwWindowStatus; /// UINT->unsigned int public uint cxWindowBorders; /// UINT->unsigned int public uint cyWindowBorders; /// ATOM->WORD->unsigned short public ushort atomWindowType; /// WORD->unsigned short public ushort wCreatorVersion; } [System.Runtime.InteropServices.DllImport("user32.dll")] private static extern bool MoveWindow(IntPtr hWnd, int X, int Y, int nWidth, int nHeight, bool bRepaint); [System.Runtime.InteropServices.DllImport("user32.dll")] private static extern bool UpdateWindow(IntPtr hWnd); private void button2_Click(object sender, EventArgs e) { using (System.Diagnostics.Process browserProc = new System.Diagnostics.Process()) { browserProc.StartInfo.FileName = webBrowser1.Url.ToString(); browserProc.StartInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Minimized; int i= browserProc.Id; tagWINDOWINFO info = new tagWINDOWINFO(); info.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(info); browserProc.Start(); GetWindowInfo(browserProc.MainWindowHandle, ref info); browserProc.WaitForInputIdle(); string str = browserProc.MainWindowTitle; MoveWindow(browserProc.MainWindowHandle, 100, 100, 100, 100, true); UpdateWindow(browserProc.MainWindowHandle); } } But I get an "No process is associated with this object". Could anyone help? Or mb other ideas how to run new browser window whith specified size and location?

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  • typedef of a template with a template type as its parameter

    - by bryan sammon
    Im having a problem with a typedef below, I can seem to get it right: template <typename T> struct myclass1 { static const int member1 = T::GetSomeInt(); }; template <int I> struct myclass2 { typedef myclass1< myclass2<I> > anotherclass; static int GetSomeInt(); }; anotherclass MyObj1; // ERROR here not instantiating the class When I try and initialize a anotherclass object, it gives me an error. Any idea what I am doing wrong? There seems to be a problem with my typedef. Any help is appreciated, Thanks Bryan

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  • Using numeric_limits::max() in constant expressions

    - by FireAphis
    Hello, I would like to define inside a class a constant which value is the maximum possible int. Something like this: class A { ... static const int ERROR_VALUE = std::numeric_limits<int>::max(); ... } This declaration fails to compile with the following message: numeric.cpp:8: error: 'std::numeric_limits::max()' cannot appear in a constant-expression numeric.cpp:8: error: a function call cannot appear in a constant-expression I understand why this doesn't work, but two things look weird to me: It seems to me a natural decision to use the value in constant expressions. Why did the language designers decide to make max() a function thus not allowing this usage? The spec claims in 18.2.1 that For all members declared static const in the numeric_limits template, specializations shall define these values in such a way that they are usable as integral constant expressions. Doesn't it mean that I should be able to use it in my scenario and doesn't it contradict the error message? Thank you.

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  • Google webmaster tools: parameters that only apply on one page

    - by Imagine digital
    I'm trying to get my e-commerce website on google and still figuring out how it all works. Now, I have seen this feature named URL-parameters, allowing me to set different parameters that affect page content to be indexed (one can also set parameters that do not affect the page, but for me that does not apply..). The question I have about this is whether and how I should add parameters that I only have on some pages of my site. example: The homepage of my site is www.mysite.nl. no parameters at all. But when a user clicks the navigation bar, it links to www.mysite.nl/itemList.php?category=&....subCategory=.... The parameters category and subCategory define whether there is content on my itemList page and what content that is. It gets matching products out of my database based on those 2 variables. The question: How do I make sure that I apply the google URL Parameters function decently for my website?

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  • Use native HBitmap in C# while preserving alpha channel/transparency. Please check this code, it works on my computer...

    - by David
    Let's say I get a HBITMAP object/handle from a native Windows function. I can convert it to a managed bitmap using Bitmap.FromHbitmap(nativeHBitmap), but if the native image has transparency information (alpha channel), it is lost by this conversion. There are a few questions on Stack Overflow regarding this issue. Using information from the first answer of this question (How to draw ARGB bitmap using GDI+?), I wrote a piece of code that I've tried and it works. It basically gets the native HBitmap width, height and the pointer to the location of the pixel data using GetObject and the BITMAP structure, and then calls the managed Bitmap constructor: Bitmap managedBitmap = new Bitmap(bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); As I understand (please correct me if I'm wrong), this does not copy the actual pixel data from the native HBitmap to the managed bitmap, it simply points the managed bitmap to the pixel data from the native HBitmap. And I don't draw the bitmap here on another Graphics (DC) or on another bitmap, to avoid unnecessary memory copying, especially for large bitmaps. I can simply assign this bitmap to a PictureBox control or the the Form BackgroundImage property. And it works, the bitmap is displayed correctly, using transparency. When I no longer use the bitmap, I make sure the BackgroundImage property is no longer pointing to the bitmap, and I dispose both the managed bitmap and the native HBitmap. The Question: Can you tell me if this reasoning and code seems correct. I hope I will not get some unexpected behaviors or errors. And I hope I'm freeing all the memory and objects correctly. private void Example() { IntPtr nativeHBitmap = IntPtr.Zero; /* Get the native HBitmap object from a Windows function here */ // Create the BITMAP structure and get info from our nativeHBitmap NativeMethods.BITMAP bitmapStruct = new NativeMethods.BITMAP(); NativeMethods.GetObjectBitmap(nativeHBitmap, Marshal.SizeOf(bitmapStruct), ref bitmapStruct); // Create the managed bitmap using the pointer to the pixel data of the native HBitmap Bitmap managedBitmap = new Bitmap( bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); // Show the bitmap this.BackgroundImage = managedBitmap; /* Run the program, use the image */ MessageBox.Show("running..."); // When the image is no longer needed, dispose both the managed Bitmap object and the native HBitmap this.BackgroundImage = null; managedBitmap.Dispose(); NativeMethods.DeleteObject(nativeHBitmap); } internal static class NativeMethods { [StructLayout(LayoutKind.Sequential)] public struct BITMAP { public int bmType; public int bmWidth; public int bmHeight; public int bmWidthBytes; public ushort bmPlanes; public ushort bmBitsPixel; public IntPtr bmBits; } [DllImport("gdi32", CharSet = CharSet.Auto, EntryPoint = "GetObject")] public static extern int GetObjectBitmap(IntPtr hObject, int nCount, ref BITMAP lpObject); [DllImport("gdi32.dll")] internal static extern bool DeleteObject(IntPtr hObject); }

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  • How does a website like Mathway work?

    - by Bob
    I recently found a website called Mathway Basically, it works by allowing you to choose your "level of math" (which it uses to determine what tools it should provide to you) and then allows you to input a math problem which it then solves for you, and gives you detailed solutions (you have to try it, it's really cool). I was wondering how it worked on two levels. First off, how would they parse the math problem (and all the sometimes foreign mathematical operators)? How do they get from text to numbers, variables, and operators? Second, how do they generate the explanations? While you have to pay for the detailed solutions (which are explanations of how they solved the problem), I've seen their preview screenshots, and it looks very detailed. The explanations are given in full, accurate sentences. How would they generate something like that?

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  • ProgressBar not updating on change to Maximum through binding

    - by Tom
    <ProgressBar Foreground="Red" Background="Transparent" Value="{Binding NumFailed, Mode=OneWay}" Minimum="0" Maximum="{Binding NumTubes, Mode=OneWay, Converter={x:Static wpftools:DebuggingConverter.Instance}, ConverterParameter=Failedprogressbar}" FlowDirection="RightToLeft" Style="{DynamicResource {x:Static wpftools:CustomResources.StyleProgressBarVistaKey}}" /> This is what my progressbar looks like at the moment. The style came from http://mattserbinski.com/blog/look-and-feel-progressbar and the DebuggingConverter is a no-op converter that prints the value, type and parameter to the Console. I have verified that the converter for the Maximum is being called when my NumTubes property is changed. Basically, the ProgressBar won't redraw until the Value changes. So, if I have 2 tubes and 1 is failed, even if I add 20 more tubes, the bar is still half filled until the NumFailed changes, then the proportion is updated. I've tried adding spurious notifications of the NumFailed property, but that apparently doesn't work since the value didn't change. Ideas?

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  • Checking if date parsing is correct

    - by Javi
    Hello, I have this code for checking whether the Date is OK or not, but it's not ckecking all the cases. For example when text="03/13/2009" as this date doesn't exist in the format "dd/MM/yyyy" it parses the date as 03/01/2010. Is there any way to change this behaviour and getting an exception when I try to parse a Date which is not correct? What's the best way to do this validation? public static final String DATE_PATTERN = "dd/MM/yyyy"; public static boolean isDate(String text){ SimpleDateFormat formatter = new SimpleDateFormat(DATE_PATTERN); ParsePosition position = new ParsePosition(0); formatter.parse(text, position); if(position.getIndex() != text.length()){ return false; }else{ return true; } } Thanks.

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  • How to represent different entities that have identical behavior?

    - by Dominik
    I have several different entities in my domain model (animal species, let's say), which have a few properties each. The entities are readonly (they do not change state during the application lifetime) and they have identical behavior (the differ only by the values of properties). How to implement such entities in code? Unsuccessful attempts: Enums I tried an enum like this: enum Animals { Frog, Duck, Otter, Fish } And other pieces of code would switch on the enum. However, this leads to ugly switching code, scattering the logic around and problems with comboboxes. There's no pretty way to list all possible Animals. Serialization works great though. Subclasses I also thought about where each animal type is a subclass of a common base abstract class. The implementation of Swim() is the same for all Animals, though, so it makes little sense and serializability is a big issue now. Since we represent an animal type (species, if you will), there should be one instance of the subclass per application, which is hard and weird to maintain when we use serialization. public abstract class AnimalBase { string Name { get; set; } // user-readable double Weight { get; set; } Habitat Habitat { get; set; } public void Swim(); { /* swim implementation; the same for all animals but depends uses the value of Weight */ } } public class Otter: AnimalBase{ public Otter() { Name = "Otter"; Weight = 10; Habitat = "North America"; } } // ... and so on Just plain awful. Static fields This blog post gave me and idea for a solution where each option is a statically defined field inside the type, like this: public class Animal { public static readonly Animal Otter = new Animal { Name="Otter", Weight = 10, Habitat = "North America"} // the rest of the animals... public string Name { get; set; } // user-readable public double Weight { get; set; } public Habitat Habitat { get; set; } public void Swim(); } That would be great: you can use it like enums (AnimalType = Animal.Otter), you can easily add a static list of all defined animals, you have a sensible place where to implement Swim(). Immutability can be achieved by making property setters protected. There is a major problem, though: it breaks serializability. A serialized Animal would have to save all its properties and upon deserialization it would create a new instance of Animal, which is something I'd like to avoid. Is there an easy way to make the third attempt work? Any more suggestions for implementing such a model?

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  • More advanced usage of interfaces

    - by owca
    To be honest I'm not quite sure if I understand the task myself :) I was told to create class MySimpleIt, that implements Iterator and Iterable and will allow to run the provided test code. Arguments and variables of objects cannot be either Collections or arrays. The code : MySimpleIt msi=new MySimple(10,100, MySimpleIt.PRIME_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.ODD_NUMBERS); msi.setLimits(15,30); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.EVEN_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); The result I should obtain : 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 15 17 19 21 23 25 27 29 16 18 20 22 24 26 28 30 And here's my code : import java.util.Iterator; interface MySimpleIterator{ static int ODD_NUMBERS=0; static int EVEN_NUMBERS = 1; static int PRIME_NUMBERS = 2; int setType(int i); } public class MySimpleIt implements Iterable, Iterator, MySimpleIterator { public MySimple my; public MySimpleIt(MySimple m){ my = m; } public int setType(int i){ my.numbers = i; return my.numbers; } public void setLimits(int d, int u){ my.down = d; my.up = u; } public Iterator iterator(){ Iterator it = this.iterator(); return it; } public void remove(){ } public Object next(){ Object o = new Object(); return o; } public boolean hasNext(){ return true; } } class MySimple { public int down; public int up; public int numbers; public MySimple(int d, int u, int n){ down = d; up = u; numbers = n; } } In the test code I have error in line when creating MySimpleIt msi object, as it finds MySimple instead of MySimpleIt. Also I have errors in for-each loops, because compiler wants 'ints' there instead of Object. Anyone has any idea on how to solve it ?

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  • Try-Catch-Throw in the same Java class

    - by Carlos
    Is it possible to catch a method in the current class the try-catch block is running on? for example: public static void arrayOutOfBoundsException(){ System.out.println("Array out of bounds"); } ..... public static void doingSomething(){ try { if(something[i] >= something_else); } catch (arrayOutOfBoundsException e) { System.out.println("Method Halted!, continuing doing the next thing"); } } If this is possible how will it be the correct way to call the catch method? If this is not possible, could anyone point me in the right direction, of how to stop an exception from halting my program execution in Java without having to create any new classes in the package, or fixing the code that produces ArrayOutOfBoundsException error. Thanks in Advance, A Java Rookie

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  • How to access a flash object embedded via swfobject's embedSWF?

    - by Andree
    Hi there, I have to call an ActionScript method via Javascript, but I have a problem accessing the flash object itself. I embed the flash file via the help of swfobject. Previously, when I use the static publishing approach, I could easily get the flash object by calling these methods: swfobject.registerObject("flash_object", "9", "expressInstall.swf"); var flash_object = swfobject.getObjectById("flash_object"); For some technical reasons, now I have to use the dynamic publishing approach (using swfobject.embedSWF). But, as mentioned in the documentation, the method getObjectById can only be used if you use static publishing approach. Now, how can I access the flash object? Cheers, Andree

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