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  • Comparison of algorithmic approaches to the N queens problem

    - by iceman
    I wanted to evaluate performance comparisons for various approaches to solving the N queens problem. Mainly AI metaheuristics based algorithms like simulated annealing, tabu search and genetic algorithm etc compared to exact methods(like backtracking). Is there any code available for study? A lot of real-world optimization problems like it consider cooperative schemes between exact methods and metaheuristics.

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  • java annotations - problem with calling a locator class from a Vaadin Project

    - by George
    Hello, I'm not sure how to explain this without writing several pages so I hope the actual code is more expressive. I've made a jar containing multiple annotation declaration similar to the following: @Target(ElementType.PACKAGE) @Retention(RetentionPolicy.RUNTIME) public @interface MarkedPackage { } then I have made a test jar containing several classes in several packages and marked just one package with the above annotation (with package-info.java) like below: @myPackage.MarkedPackage package package.test.jar; this jar had in its build path the jar containing the annotations. then I made a static class that has a method (LoadPlugins) that retrieves a list with all the jars of a directory. Then it searches through the jars for the 'package-info' class and checks if that classes package contains the MarkedPackage annotation. by calling this: if (checkPackageAnnotation(thisClass.getPackage())) where thisClass is the package-info class retrieved via a classloader. and: public static boolean checkPackageAnnotation(AnnotatedElement elem) { System.out.println(elem.getAnnotations().length); if (elem == null || !elem.isAnnotationPresent(MarkedPackage.class)) return false; return true; } the elem.getAnnotatios().length is there for debug purposes. And the problem appears when I call the method from the static class: if I call it from a main function: public class MyMain { public static void main(String[] args){ PluginUtils.LoadPlugins(); } } everything works perfectly it displays '1' from that System.out.println(elem.getAnnotations().length); But if I call it from a button from my Vaadin project: header.addComponent(new Button("CallThat", new Button.ClickListener() { public void buttonClick(ClickEvent event) { PluginUtils.LoadPlugins(); } })); It displays '0' from that System.out.println(elem.getAnnotations().length); Also I should mention that I created the main inside my Vaadin project so it would have the exact same build path and resources. Is there a problem with web applications and that "@Retention(RetentionPolicy.RUNTIME)" ? hope I was clear enough... Hope someone has a solution for me... If you need more information - let me know. Thank you.

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  • When using delegates, need better way to do sequential processing

    - by Padawan
    I have a class WebServiceCaller that uses NSURLConnection to make asynchronous calls to a web service. The class provides a delegate property and when the web service call is done, it calls a method webServiceDoneWithXXX on the delegate. There are several web service methods that can be called, two of which are say GetSummary and GetList. The classes that use WebServiceCaller initially need both the summary and list so they are written like this: -(void)getAllData { [webServiceCaller getSummary]; } -(void)webServiceDoneWithGetSummary { [webServiceCaller getList]; } -(void)webServiceDoneWithGetList { ... } This works but there are at least two problems: The calls are split across delegate methods so it's hard to see the sequence at a glance but more important it's hard to control or modify the sequence. Sometimes I want to call just GetSummary and not also GetList so I would then have to use an ugly class-level state variable that tells webServiceDoneWithGetSummary whether to call GetList or not. Assume that GetList cannot be done until GetSummary completes and returns some data which is used as input to GetList. Is there a better way to handle this and still get asynchronous calls? Update based on Matt Long's answer: Using notifications instead of a delegate, it looks like I can solve problem #2 by setting a different selector depending on whether I want the full sequence (GetSummary+GetList) or just GetSummary. Both observers would still use the same notification name when calling GetSummary. I would have to write two separate methods to handle GetSummaryDone instead of using a single delegate method (where I would have needed some class-level variable to tell whether to then call GetList). -(void)getAllData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getSummaryDoneAndCallGetList:)                  name:kGetSummaryDidFinish object:nil];     [webServiceCaller getSummary]; } -(void)getSummaryDoneAndCallGetList { [NSNotificationCenter removeObserver] //process summary data [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getListDone:)                  name:kGetListDidFinish object:nil];     [webServiceCaller getList]; } -(void)getListDone { [NSNotificationCenter removeObserver] //process list data } -(void)getJustSummaryData { [[NSNotificationCenter defaultCenter] addObserver:self              selector:@selector(getJustSummaryDone:) //different selector but                  name:kGetSummaryDidFinish object:nil]; //same notification name     [webServiceCaller getSummary]; } -(void)getJustSummaryDone { [NSNotificationCenter removeObserver] //process summary data } I haven't actually tried this yet. It seems better than having state variables and if-then statements but you have to write more methods. I still don't see a solution for problem 1.

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  • core dump during std::_List_node_base::unhook()

    - by Ron
    I have a program where std::list is used. The program uses threads which act on the std::list as producers and consumers. When a message is dealt with by the consumer, it is removed from the list using pop_front(). But, during pop_front, there is a core dump. The gdb trace is as below. could you help getting me some insights into this issue? (gdb) bt full 0 0xf7531d7b in std::_List_node_base::unhook () from /usr/lib/libstdc++.so.6 No symbol table info available. 1 0x0805c600 in std::list ::_M_erase (this=0x806b08c, __position={_M_node = 0x8075308}) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:1169 __n = (class std::_List_node<myMsg> *) 0x0 2 0x0805c6af in std::list ::pop_front (this=0x806b08c) at /opt/target/usr/include/c++/4.2.0/bits/stl_list.h:750 No locals. 3 0x0805afb6 in Base::run () at ../../src/Base.cc:342 nSentBytes = 130 tmpnm = {_vptr.myMsg = 0x80652c0, m_msg = 0x8075140 "{0130,MSG_TYPE=ND_FUNCTION,ORG_PNAME=P01vm01Ax,FUNCTION=LOG,PARAM_CNT=3,DATETIME=06/12/2010 02:59:26.187,LOGNAME=N,ENTRY=Debug 0 }", m_from = 0x8096ee0 "P01vm01Ax", m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} newMsg = {_vptr.myMsg = 0x80652c0, m_msg = 0x0, m_from = 0x0, m_to = 0x0, static m_logged = false, static m_pLogMutex = {_data = {_lock = 0, __count = 0, __owner = 0, __kind = 0, _nusers = 0, {_spins = 0, _list = {_next = 0x0}}}, __size = '\0' , __align = 0}} strBuffer = "{0440,MSG_TYPE=NG_FUNCTION,ORG_PNAME=mach01./opt/abc/VAvsk/abc/comp/DML/gendrs.pl.17560,DST_PNAME=P01vm01Ax,FUNCTION=DRS_REPLICATE,CAUSE_DML_ERROR=N,CORRUPT_DATA=N,CORRUPT_HEADER=N,DEBUG=Y,EXTENDED_RU"... fds = {{fd = 5, events = 1, revents = 0}} retval = 0 iWaitTime = 0 4 0x0805b277 in startRun () at ../../src/Base.cc:454 No locals. 5 0xf7effe7b in start_thread () from /lib/libpthread.so.0 No symbol table info available. 6 0xf744d82e in clone () from /lib/libc.so.6 No symbol table info available.

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  • mainframe in Joomla

    - by Casebash
    The hello world tutorial for Joomla states: $mainframe is a global variable in Joomla that has lots of useful methods attached to it. How do I find out what these methods are? I tried searching through their documentation, but I couldn't find any clues.

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  • [Symfony 1.2: ckWebServicePlugin 3.0.0] Module name in SOAP requests, how to get rid of them?

    - by Henri
    When I generate a WSDL file with ./symfony webservice:generate-wsdl (where is 'frontend', is 'soap' and is 'http://localhost ') I get a nice soap.wsdl file which works like it should. Except, the methods are not named 'justAMethod' but 'soapService_justAMethod' (where soapService is the module which holds the SOAP methods). How do I omit the module name in the SOAP method names? I know this is possible since the previous release of the software had no module name in the SOAP method names.

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  • How do I use the information about exceptions a method throws in .NET in my code?

    - by dotnetdev
    For many methods in .NET, the exceptions they can potentially throw can be as many as 7-8 (one or two methods in XmlDocument, Load() being one I think, can throw this many exceptions). Does this mean I have to write 8 catch blocks to catch all of these exceptions (it is best practise to catch an exception with a specific exception block and not just a general catch block of type Exception). How do I use this information? Thanks

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  • How to take advantage of an auto-property when refactoring this .Net 1.1 sample?

    - by Hamish Grubijan
    I see a lot of legacy .Net 1.1-style code at work like in example below, which I would like to shrink with the help of an auto-property. This will help many classes shrink by 30-40%, which I think would be good. public int MyIntThingy { get { return _myIntThingy; } set { _myIntThingy = value; } } private int _myIntThingy = -1; This would become: public int MyIntThingy { get; set; } And the only question is - where do I set MyIntThingy = -1;? If I wrote the class from the start, then I would have a better idea, but I did not. An obvious answer would be: put it in the constructor. Trouble is: there are many constructors in this class. Watching the initialization to -1 in the debugger, I see it happen (I believe) before the constructor gets called. It is almost as if I need to use a static constructor as described here: http://www.c-sharpcorner.com/uploadfile/cupadhyay/staticconstructors11092005061428am/staticconstructors.aspx except that my variables are not static. Java's static initializer comes to mind, but again - my variables are not static. http://www.glenmccl.com/tip_003.htm I want to make stylistic but not functional changes to this class. As crappy as it is, it has been tested and working for a few years now. breaking the functionality would be bad. So ... I am looking for shorter, sweeter, cuter, and yet EQUIVALENT code. Let me know if you have questions.

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  • NetBeans shortcut key for collapsing/expanding a method

    - by Stefanos Kargas
    JAVA - NETBEANS This is an IDE question I am always working with collapsed methods, because I want to be able to see my methods all together. This is a little time consuming because I have to use the mouse to scroll up to the declaration of the method and click on the - (minus) icon. And then respectively go to the method I want to work on and click on the + (plus) icon. Is there a way through a keyboard shortcut to do the collapse (and respectively the expand)?

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  • Enabling/Disabling Aero from a Windows Service

    - by rgould
    I have some code to enable/disable the Windows Aero service in Vista, and I would like to run it in a Windows Service. The code works in a standalone application, but when I run it from a Service, nothing happens. No errors or exceptions are thrown. I realise that running code in a service is a different scope than running code in an application, but in this case, how would I enable/disable Aero from the service? Is this even possible? Here is the code I am working with: public static readonly uint DWM_EC_DISABLECOMPOSITION = 0; public static readonly uint DWM_EC_ENABLECOMPOSITION = 1; [DllImport("dwmapi.dll", EntryPoint="DwmEnableComposition")] protected static extern uint Win32DwmEnableComposition(uint uCompositionAction); public static bool EnableAero() { Win32DwmEnableComposition(DWM_EC_ENABLECOMPOSITION); } Edit: It turns out that the DwmEnableComposition call is returning HRESULT 0x80070018, or ERROR_BAD_LENGTH. Seems like a strange error, since the code works when not running as a service. I also tried changing the entire thing to the following code, but got the same result. It sets the window station and desktop, and it seems to be correct, but the call to DwmEnableComposition results in the same error. I've not included the PInvoke declarations for brevity. protected override void OnStop() { IntPtr winStation = OpenWindowStation("winsta0", true, 0x10000000 /* GENERIC_ALL */); if (winStation == null || winStation.ToInt32() == 0) { String err = new Win32Exception(Marshal.GetLastWin32Error()).Message; } if (!SetProcessWindowStation(winStation)) { String err = new Win32Exception(Marshal.GetLastWin32Error()).Message; } uint thread = GetCurrentThreadId(); IntPtr hdesk = OpenInputDesktop(0, false, 0x10000000 /* GENERIC_ALL */); if (hdesk == null || hdesk.ToInt32() == 0) { String err = new Win32Exception(Marshal.GetLastWin32Error()).Message; } if (!SetThreadDesktop(hdesk)) { String err = new Win32Exception(Marshal.GetLastWin32Error()).Message; } uint result = Win32DwmEnableComposition(DWM_EC_DISABLECOMPOSITION); if (result != 0) { String err = new Win32Exception(Marshal.GetLastWin32Error()).Message; } }

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  • WPF EventRouting to Children

    - by Shaun Bowe
    Is there any way to broadcast a RoutedEvent to all of my children in WPF? For example lets say I have a Window that has 4 children. 2 of them know about the RoutedEvent 'DisplayYourself' and are listening for it. How can I raise this event from the window and have it sent to all children? I looked at RoutingStrategy and Bubble is the wrong direction, Tunnel and Direct don't work because I don't know which children I want to send this to. I just want to broadcast this message and have whoever cares about it handle it. update: I declared the events in a static class. public static class StaticEventClass { public static readonly RoutedEvent ClickEvent = EventManager.RegisterRoutedEvent("Click", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(StaticEventClass)); public static readonly RoutedEvent DrawEvent = EventManager.RegisterRoutedEvent("Draw", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(StaticEventClass)); } The problem is when I raise the event from my window, the children never see it. RoutedEventArgs args = new RoutedEventArgs(StaticEventClass.DrawEvent, this); this.RaiseEvent(args); update again.. Here is the handler in the child. public ChildClass() { this.AddHandler(StaticEventClass.DrawEvent, new RoutedEventHandler(ChildClass_Draw)); }

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  • Fluent NHibernate Map to private/protected Field that has no exposing Property

    - by Jon Erickson
    I have the following Person and Gender classes (I don't really, but the example is simplified to get my point across), using NHibernate (Fluent NHibernate) I want to map the Database Column "GenderId" [INT] value to the protected int _genderId field in my Person class. How do I do this? FYI, the mappings and the domain objects are in separate assemblies. public class Person : Entity { protected int _genderId; public virtual int Id { get; private set; } public virtual string Name { get; private set; } public virtual Gender Gender { get { return Gender.FromId(_genderId); } } } public class Gender : EnumerationBase<Gender> { public static Gender Male = new Gender(1, "Male"); public static Gender Female = new Gender(2, "Female"); private static readonly Gender[] _genders = new[] { Male, Female }; private Gender(int id, string name) { Id = id; Name = name; } public int Id { get; private set; } public string Name { get; private set; } public static Gender FromId(int id) { return _genders.Where(x => x.Id == id).SingleOrDefault(); } }

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  • Why is my GUI unresponsive while a SwingWorker thread runs?

    - by Starchy
    Hello, I have a SwingWorker thread with an IOBound task which is totally locking up the interface while it runs. Swapping out the normal workload for a counter loop has the same result. The SwingWorker looks basically like this: public class BackupWorker extends SwingWorker<String, String> { private static String uname = null; private static String pass = null; private static String filename = null; static String status = null; BackupWorker (String uname, String pass, String filename) { this.uname = uname; this.pass = pass; this.filename = filename; } @Override protected String doInBackground() throws Exception { BackupObject bak = newBackupObject(uname,pass,filename); return "Done!"; } } The code that kicks it off lives in a class that extends JFrame: public void actionPerformed(ActionEvent event) { String cmd = event.getActionCommand(); if (BACKUP.equals(cmd)) { SwingUtilities.invokeLater(new Runnable() { public void run() { final StatusFrame statusFrame = new StatusFrame(); statusFrame.setVisible(true); SwingUtilities.invokeLater(new Runnable() { public void run () { statusFrame.beginBackup(uname,pass,filename); } }); } }); } } Here's the interesting part of StatusFrame: public void beginBackup(final String uname, final String pass, final String filename) { worker = new BackupWorker(uname, pass, filename); worker.execute(); try { System.out.println(worker.get()); } catch (InterruptedException e) { e.printStackTrace(); } catch (ExecutionException e) { e.printStackTrace(); } } } So far as I can see, everything "long-running" is handled by the worker, and everything that touches the GUI on the EDT. Have I tangled things up somewhere, or am I expecting too much of SwingWorker?

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  • Partially constructed object / Multi threading

    - by reto
    Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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  • DataReader already open when using LINQ

    - by Jamie Dixon
    I've got a static class containing a static field which makes reference to a wrapper object of a DataContext. The DataContext is basically generated by Visual Studio when we created a dbml file & contains methods for each of the stored procedures we have in the DB. Our class basically has a bunch of static methods that fire off each of these stored proc methods & then returns an array based on a LINQ query. Example: public static TwoFieldBarData[] GetAgesReportData(string pct) { return DataContext .BreakdownOfUsersByAge(Constants.USER_MEDICAL_PROFILE_KEY, pct) .Select(x => new TwoFieldBarData(x.DisplayName, x.LeftValue, x.RightValue, x.TotalCount)) .ToArray(); } Every now and then, we get the following error: There is already an open DataReader associated with this Command which must be closed firs This is happening intermittently and I'm curious as to what is going on. My guess is that when there's some lag between one method executing and the next one firing, it's locking up the DataContext and throwing the error. Could this be a case for wrapping each of the DataContext LINQ calls in a lock(){} to obtain exclusivity to that type and ensure other requests are queued?

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  • Flex URLRequest and .NET authorization

    - by user252160
    can I make role based authorization when sending requests to an ASP.NET MVC backend system. I am calling action methods and expecting JSON results, however, some action methods are decorated with the [Authorize] attribute, others require some role privileges to be present. I certainly hope that passing authorization data with every request is possible

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  • Java - when to use notify or notifyAll?

    - by mdma
    Why does java.lang.Object have two notify methods - notify and notifyAll? It seems that notifyAll does at least everything notify does, so why not just use notifyAll all the time? If notifyAll is used instead of notify, is the program still correct, and vice versa? What influences the choice between these two methods?

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  • Threading questions

    - by JK
    If I spawn a secondary thread and the threaded method calls other methods, are those methods run in the secondary thread or the main thread? Is there a way to determine on which thread a specified piece of code is being run?

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  • Ninject: Shared DI/IoC container

    - by joblot
    Hi I want to share the container across various layers in my application. I started creating a static class which initialises the container and register types in the container. public class GeneralDIModule : NinjectModule { public override void Load() { Bind().To().InSingletonScope(); } } public abstract class IoC { private static IKernel _container; public static void Initialize() { _container = new StandardKernel(new GeneralDIModule(), new ViewModelDIModule()); } public static T Get<T>() { return _container.Get<T>(); } } I noticed there is a Resolve method as well. What is the difference between Resolve and Get? In my unit tests I don’t always want every registered type in my container. Is there a way of initializing an empty container and then register types I need. I’ll be mocking types as well in unit test so I’ll have to register them as well. There is an Inject method, but it says lifecycle of instance is not managed? Could someone please set me in right way? How can I register, unregister objects and reset the container. Thanks

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  • LinkedList parameters in Java

    - by Walt
    Hi there, I created a program that contains linked lists that are passed various methods. While this works just fine in Java... a style checker program we have to use doesn't like it It says: Declaring variables, return values or parameters of type 'LinkedList' is not allowed. If I declare them as simply List then I don't have access to the methods I want. What should I do?

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  • Implement LINQ to Entities unsupported method

    - by Dan
    Hi! LINQ to Entities has many LINQ methods marked as "Unsupported" (http://msdn.microsoft.com/en-us/library/bb738550.aspx). Is any way to implement some of these methods by hands? Or I should wait next release of EF? I'm especially needing this method: IQueryable<TResult> Select<TSource, TResult>(this IQueryable<TSource> source, Expression<Func<TSource, int, TResult>> selector) Thanks

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  • Rails method as a nested resource

    - by Blastula
    Hello, I'm wondering about the clever way to do this... I have methods that return a value when passed an an object as parameter, such as: <%= average_rainfall(@location) % I'd like to use the exact same methods as a nested resource to call via jQuery/Ajax, like so: .load('/location/8/average_rainfall') I understand how to define the route, but how do I tell my method to 'find' /location/8 and use that as it's parameter instead of @location as expected? Thanks!

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  • Communicating with remote server in Android

    - by primal
    Hi, As part of the college mini-project, I am developing a micro-blogging platform for Android. I am planning to use Django framework in python to handle the communication between Android and remote server so as to make database API independent. I heard its best practice to use HTTP methods for the communication. Which is the best site/book to learn using HTTP methods for Android? I

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  • JFrame that has multiple layers

    - by phunehehe
    Hello, I have a window that has two layers: a static background and a foreground that contains moving objects. My idea is to draw the background just once (because it's not going to change), so I make the changing panel transparent and add it on top of the static background. Here is the code for this: public static void main(String[] args) { JPanel changingPanel = new JPanel() { @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.RED); g.fillRect(100, 100, 100, 100); } }; changingPanel.setOpaque(false); JPanel staticPanel = new JPanel(); staticPanel.setBackground(Color.BLUE); staticPanel.setLayout(new BorderLayout()); staticPanel.add(changingPanel); JFrame frame = new JFrame(); frame.add(staticPanel); frame.setSize(800, 600); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } This piece of code gives me the correct image I want, but every time I repaint changingPanel, staticPanel gets repainted as well (which is obviously against the whole idea of painting the static panel just once). Can somebody show me what's wrong? FYI I am using the javax.swing.Timer to recalculate and repaint the changing panel 24 times every second.

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