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  • Stuck on Object scope in Java

    - by ivor
    Hello, I'm working my way through an exercise to understand Java, and basically I need to merge the functionality of two classes into one app. I'm stuck on one area though - the referencing of objects across classes. What I have done is set up a gui in one class (test1), and this has a textfield in ie. chatLine = new JTextField(); in another class(test2), I was planning on leaving all the functionality in there and referencing the various gui elements set up in test1 - like this test1.chatLine I understand this level of referencing, I tested this by setting up a test method in the test2 class public static void testpass() { test1.testfield.setText("hello"); } I'm trying to understand how to implement the more complex functionality in test2 class though, specifically this existing code; test1.chatLine.addActionListener(new ActionAdapter() { public void actionPerformed(ActionEvent e) { String s = Game.chatLine.getText(); if (!s.equals("")) { appendToChatBox("OUTGOING: " + s + "\n"); Game.chatLine.selectAll(); // Send the string sendString(s); } } }); This is the bit I'm stuck on, if I should be able to do this - as it's failing on the compile, can I add the actionadapter stuff to the gui element thats sat in test1, but do this from test2 - I'm wondering if I'm trying to do something that's not possible. Hope this makes sense, I'm pretty confused over this - I'm trying to understand how the scope and referencing works. Ideally what i'm trying to achieve is one class that has all the main stuff in, the gui etc, then all the related functionality in the other class, and target the first class's gui elements with the results etc. Any thoughts greatly appreciated.

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  • Can I get rid of this read lock?

    - by Pieter
    I have the following helper class (simplified): public static class Cache { private static readonly object _syncRoot = new object(); private static Dictionary<Type, string> _lookup = new Dictionary<Type, string>(); public static void Add(Type type, string value) { lock (_syncRoot) { _lookup.Add(type, value); } } public static string Lookup(Type type) { string result; lock (_syncRoot) { _lookup.TryGetValue(type, out result); } return result; } } Add will be called roughly 10/100 times in the application and Lookup will be called by many threads, many of thousands of times. What I would like is to get rid of the read lock. How do you normally get rid of the read lock in this situation? I have the following ideas: Require that _lookup is stable before the application starts operation. The could be build up from an Attribute. This is done automatically through the static constructor the attribute is assigned to. Requiring the above would require me to go through all types that could have the attribute and calling RuntimeHelpers.RunClassConstructor which is an expensive operation; Move to COW semantics. public static void Add(Type type, string value) { lock (_syncRoot) { var lookup = new Dictionary<Type, string>(_lookup); lookup.Add(type, value); _lookup = lookup; } } (With the lock (_syncRoot) removed in the Lookup method.) The problem with this is that this uses an unnecessary amount of memory (which might not be a problem) and I would probably make _lookup volatile, but I'm not sure how this should be applied. (John Skeets' comment here gives me pause.) Using ReaderWriterLock. I believe this would make things worse since the region being locked is small. Suggestions are very welcome.

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  • selecting a row by means of a button ... using didSelectRowAtIndexPath

    - by John Smith
    hey people , I have a question concerning a button I would like to create which selects my previous selected row. This is what I came up so far but since I'm new with the functionality and such I could definately use some pointers I created a toolbar with a button and behind this button is the following action. -(void)clickRow { selectedRow = [self.tableView indexPathForSelectedRow]; [self.tableView:[self tableView] didSelectRowAtIndexPath:selectedRow]; } in my didSelectRowAtIndexPath there is a rootViewController being pushed rvController = [RootViewController alloc] ...etc So what I would like is my function clickRow to select the row and push the new rootviewcontroller (which has the right info since I'm using a tree ). I tried something like this as well -(void)clickRow { NSDictionary *dictionary = [self.tableDataSource objectAtIndex:indexPath.row]; NSArray *Children = [dictionary objectForKey:@"Children"]; rvController = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:[NSBundle mainBundle]]; rvController.CurrentLevel += 1; rvController.CurrentTitle = [dictionary objectForKey:@"Title"]; [self.navigationController pushViewController:rvController animated:YES]; rvController.tableDataSource = Children; [rvController release]; } The last function works a little but a little is not enough;) For instance if I press the middle row or any other it constantly selects the toprow. thnx all for those of you reading and trying to help

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  • Creating futures using Apple's GCD

    - by jer
    I'm working on a library which implements the actor model on top of Grand Central Dispatch (specifically the C level API libdispatch). Basically a brief overview of my system is as such: Communication happens between actors using messages Multicast communication only (one actor to many actors) Senders and receivers are decoupled from one another using a blackboard where messages are pushed to. Messages are sent in the default queue asynchronously using dispatch_group_async() once a message gets pushed onto the blackboard. I'm trying to implement futures in the language right now, so I've created a new type which holds some information: A group of its own The value being 'returned' However, I have a problem since dispatch_block_t is of type void (^)(void) so it doesn't return anything. So my idea of in my future_new() function of setting up another group which can be used to execute a block returning a result, which I can store in my "value" member in my future_t structure, isn't going to work. The rest of the futures implementation is very clear, except it all depends on being able to get the value into the future back from the actor, acting on the message. When using the library, it would greatly reduce its usefulness if I had to ask users (and myself) to be aware when futures were going to be used by other parts of the system—It just isn't practical. I'm wondering if anyone can think of a way around this?

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  • Weird camera Intent behavior

    - by David Erosa
    Hi all. I'm invoking the MediaStore.ACTION_IMAGE_CAPTURE intent with the MediaStore.EXTRA_OUTPUT extra so that it does save the image to that file. On the onActivityResult I can check that the image is being saved in the intended file, which is correct. The weird thing is that anyhow, the image is also saved in a file named something like "/sdcard/Pictures/Camera/1298041488657.jpg" (epoch time in which the image was taken). I've checked the Camera app source (froyo-release branch) and I'm almost sure that the code path is correct and wouldn't have to save the image, but I'm a noob and I'm not completly sure. AFAIK, the image saving process starts with this callback (comments are mine): private final class JpegPictureCallback implements PictureCallback { ... public void onPictureTaken(...){ ... // This is where the image is passed back to the invoking activity. mImageCapture.storeImage(jpegData, camera, mLocation); ... public void storeImage(final byte[] data, android.hardware.Camera camera, Location loc) { if (!mIsImageCaptureIntent) { // Am i an intent? int degree = storeImage(data, loc); // THIS SHOULD NOT BE CALLED WITHIN THE CAPTURE INTENT!! ....... // An finally: private int storeImage(byte[] data, Location loc) { try { long dateTaken = System.currentTimeMillis(); String title = createName(dateTaken); String filename = title + ".jpg"; // Eureka, timestamp filename! ... So, I'm receiving the correct data, but it's also being saved in the "storeImage(data, loc);" method call, which should not be called... It'd not be a problem if I could get the newly created filename from the intent result data, but I can't. When I found this out, I found about 20 image files from my tests that I didn't know were on my sdcard :) I'm getting this behavior both with my Nexus One with Froyo and my Huawei U8110 with Eclair. Could please anyone enlight me? Thanks a lot.

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  • What is wrong with locking non-static fields? What is the correct way to lock a particular instance?

    - by smartcaveman
    Why is it considered bad practice to lock non-static fields? And, if I am not locking non-static fields, then how do I lock an instance method without locking the method on all other instances of the same or derived class? I wrote an example to make my question more clear. public abstract class BaseClass { private readonly object NonStaticLockObject = new object(); private static readonly object StaticLockObject = new object(); protected void DoThreadSafeAction<T>(Action<T> action) where T: BaseClass { var derived = this as T; if(derived == null) { throw new Exception(); } lock(NonStaticLockObject) { action(derived); } } } public class DerivedClass :BaseClass { private readonly Queue<object> _queue; public void Enqueue(object obj) { DoThreadSafeAction<DerivedClass>(x=>x._queue.Enqueue(obj)); } } If I make the lock on the StaticLockObject, then the DoThreadSafeAction method will be locked for all instances of all classes that derive from BaseClass and that is not what I want. I want to make sure that no other threads can call a method on a particular instance of an object while it is locked.

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  • How do you pass a BitmapImage from a background thread to the UI thread in WPF?

    - by DanM
    I have a background thread that generates a series of BitmapImage objects. Each time the background thread finishes generating a bitmap, I would like to show this bitmap to the user. The problem is figuring out how to pass the BitmapImage from the background thread to the UI thread. This is an MVVM project, so my view has an Image element: <Image Source="{Binding GeneratedImage}" /> My view-model has a property GeneratedImage: private BitmapImage _generatedImage; public BitmapImage GeneratedImage { get { return _generatedImage; } set { if (value == _generatedImage) return; _generatedImage= value; RaisePropertyChanged("GeneratedImage"); } } My view-model also has the code that creates the background thread: public void InitiateGenerateImages(List<Coordinate> coordinates) { ThreadStart generatorThreadStarter = delegate { GenerateImages(coordinates); }; var generatorThread = new Thread(generatorThreadStarter); generatorThread.ApartmentState = ApartmentState.STA; generatorThread.IsBackground = true; generatorThread.Start(); } private void GenerateImages(List<Coordinate> coordinates) { foreach (var coordinate in coordinates) { var backgroundThreadImage = GenerateImage(coordinate); // I'm stuck here...how do I pass this to the UI thread? } } I'd like to somehow pass backgroundThreadImage to the UI thread, where it will become uiThreadImage, then set GeneratedImage = uiThreadImage so the view can update. I've looked at some examples dealing with the WPF Dispatcher, but I can't seem to come up with an example that addresses this issue. Please advise.

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  • C# 4.0 'dynamic' doesn't set ref/out arguments

    - by Buu Nguyen
    I'm experimenting with DynamicObject. One of the things I try to do is setting the values of ref/out arguments, as shown in the code below. However, I am not able to have the values of i and j in Main() set properly (even though they are set correctly in TryInvokeMember()). Does anyone know how to call a DynamicObject object with ref/out arguments and be able to retrieve the values set inside the method? class Program { static void Main(string[] args) { dynamic proxy = new Proxy(new Target()); int i = 10; int j = 20; proxy.Wrap(ref i, ref j); Console.WriteLine(i + ":" + j); // Print "10:20" while expect "20:10" } } class Proxy : DynamicObject { private readonly Target target; public Proxy(Target target) { this.target = target; } public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { int i = (int) args[0]; int j = (int) args[1]; target.Swap(ref i, ref j); args[0] = i; args[1] = j; result = null; return true; } } class Target { public void Swap(ref int i, ref int j) { int tmp = i; i = j; j = tmp; } }

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  • accessing a method from a button within a class?

    - by flo
    #import "GameObject.h" #import "Definitions.h" @implementation GameObject @synthesize owner; @synthesize state; @synthesize mirrored; @synthesize button; @synthesize switcher; - (id) init { if ( self = [super init] ) { [self setOwner: EmptyField]; button = [UIButton buttonWithType:UIButtonTypeCustom]; [self setSwitcher: FALSE]; } return self; } - (UIButton*) display{ button.frame = CGRectMake(0, 0, GO_Width, GO_Height); [button setBackgroundImage:[UIImage imageNamed:BlueStone] forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside]; return button; } -(void)buttonPressed:(id) sender { //... } } - (void) dealloc { [super dealloc]; } @end Hi! i would like to know if the above is possible somehow within a class (in my case it is called GameObject) or if i HAVE to have the button call a methode in the viewcontroller... the above results with the app crashing. i would call display within a loop on the viewcontroller and id like to change some of the GameObjects instance variables within buttonPressed. Also id like to change some other stuff by calling some other methods from within buttonPressed but i think that will be the lesser of my problems ;) also id like to know how i can pass some variables to the buttonPressed method... cant find it anywhere :( help on this one would be much appreciated ;) thanks flo

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  • Generating a field setter and getter with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • Should java try blocks be scoped as tightly as possible?

    - by isme
    I've been told that there is some overhead in using the Java try-catch mechanism. So, while it is necessary to put methods that throw checked exception within a try block to handle the possible exception, it is good practice performance-wise to limit the size of the try block to contain only those operations that could throw exceptions. I'm not so sure that this is a sensible conclusion. Consider the two implementations below of a function that processes a specified text file. Even if it is true that the first one incurs some unnecessary overhead, I find it much easier to follow. It is less clear where exactly the exceptions come from just from looking at statements, but the comments clearly show which statements are responsible. The second one is much longer and complicated than the first. In particular, the nice line-reading idiom of the first has to be mangled to fit the readLine call into a try block. What is the best practice for handling exceptions in a funcion where multiple exceptions could be thrown in its definition? This one contains all the processing code within the try block: void processFile(File f) { try { // construction of FileReader can throw FileNotFoundException BufferedReader in = new BufferedReader(new FileReader(f)); // call of readLine can throw IOException String line; while ((line = in.readLine()) != null) { process(line); } } catch (FileNotFoundException ex) { handle(ex); } catch (IOException ex) { handle(ex); } } This one contains only the methods that throw exceptions within try blocks: void processFile(File f) { FileReader reader; try { reader = new FileReader(f); } catch (FileNotFoundException ex) { handle(ex); return; } BufferedReader in = new BufferedReader(reader); String line; while (true) { try { line = in.readLine(); } catch (IOException ex) { handle(ex); break; } if (line == null) { break; } process(line); } }

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  • How do I change the base class at runtime in C#?

    - by MatthewMartin
    I may be working on mission impossible here, but I seem to be getting close. I want to extend a ASP.NET control, and I want my code to be unit testable. Also, I'd like to be able to fake behaviors of a real Label (namely things like ID generation, etc), which a real Label can't do in an nUnit host. Here a working example that makes assertions on something that depends on a real base class and something that doesn't-- in a more realistic unit test, the test would depend on both --i.e. an ID existing and some custom behavior. Anyhow the code says it better than I can: public class LabelWrapper : Label //Runtime //public class LabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } //Ugh, now I have to test FakeLabelWrapper public class FakeLabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } [TestFixture] public class UnitTest { [Test] public void Test() { //Wish this was LabelWrapper label = new LabelWrapper(new FakeBase()) LabelWrapper label = new LabelWrapper(); //FakeLabelWrapper label = new FakeLabelWrapper(); label.Text = "ToUpper"; Assert.AreEqual("TOUPPER",label.Text); StringWriter stringWriter = new StringWriter(); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); label.RenderControl(writer); Assert.AreEqual(1,label.ID); Assert.AreEqual("<span>TOUPPER</span>", stringWriter.ToString()); } } public class FakeLabel { virtual public string Text { get; set; } public void RenderControl(TextWriter writer) { writer.Write("<span>" + Text + "</span>"); } } //System Under Test internal class LabelLogic { internal string ProcessGetText(string value) { return value.ToUpper(); } internal string ProcessSetText(string value) { return value.ToUpper(); } }

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  • iphone NSMutableArray loses objects at end of method

    - by Brodie4598
    Hello - in my app, an NSMutableArray is populated with an object in viewDidLoad (eventually there will be many objects but I'm just doing one til I get it working right). I also start a timer that starts a method that needs to access the NSMutableArray every few seconds. The NSMutableArray works fine in viewDidLoad, but as soon as that method is finished, it loses the object. myApp.h @interface MyApp : UIViewController { NSMutableArray *myMutableArray; NSTimer *timer; } @property (nonatomic, retain) NSMutableArray *myMutableArray; @property (nonatomic, retain) NSTimer *timer; @end myApp.m #import "MyApp.h" @implementation MyApp @synthesize myMutableArray; - (void) viewDidLoad { cycleTimer = [NSTimer scheduledTimerWithTimeInterval:4.0 target:self selector:@selector(newCycle) userInfo: nil repeats:YES]; MyObject *myCustomUIViewObject = [[MyObject alloc]init]; [myMutableArray addObject:myCustomUIViewObject]; [myCustomUIViewObject release]; NSLog(@"%i",[myMutableArray count]); /////outputs "1" } -(void) newCycle { NSLog(@"%i",[myMutableArray count]); /////outputs "0" ?? why is this?? }

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  • Set HttpContext.Current.User from Thread.CurrentPrincipal

    - by Argons
    I have a security manager in my application that works for both windows and web, the process is simple, just takes the user and pwd and authenticates them against a database then sets the Thread.CurrentPrincipal with a custom principal. For windows applications this works fine, but I have problems with web applications. After the process of authentication, when I'm trying to set the Current.User to the custom principal from Thread.CurrentPrincipal this last one contains a GenericPrincipal. Am I doing something wrong? This is my code: Login.aspx protected void btnAuthenticate_Click(object sender, EventArgs e) { Authenticate("user","pwd"); FormsAuthenticationTicket authenticationTicket = new FormsAuthenticationTicket(1, "user", DateTime.Now, DateTime.Now.AddMinutes(30), false, ""); string ticket = FormsAuthentication.Encrypt(authenticationTicket); HttpCookie authenticationCookie = new HttpCookie(FormsAuthentication.FormsCookieName, ticket); Response.Cookies.Add(authenticationCookie); Response.Redirect(FormsAuthentication.GetRedirectUrl("user", false)); } Global.asax (This is where the problem appears) protected void Application_AuthenticateRequest(object sender, EventArgs e) { HttpCookie authCookie = Context.Request.Cookies[FormsAuthentication.FormsCookieName]; if (authCookie == null) return; if (HttpContext.Current.User != null && HttpContext.Current.User.Identity.IsAuthenticated && HttpContext.Current.User.Identity is FormsIdentity) { HttpContext.Current.User = System.Threading.Thread.CurrentPrincipal; //Here the value is GenericPrincipal } Thanks in advance for any help. }

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  • How to mix Grammar (Rules) & Dictation (Free speech) with SpeechRecognizer in C#

    - by Lee Englestone
    I really like Microsofts latest speech recognition (and SpeechSynthesis) offerings. http://msdn.microsoft.com/en-us/library/ms554855.aspx http://estellasays.blogspot.com/2009/04/speech-recognition-in-cnet.html However I feel like I'm somewhat limited when using grammars. Don't get me wrong grammars are great for telling the speech recognition exactly what words / phrases to look out for, however what if I want it to recognise something i've not given it a heads up about? Or I want to parse a phrase which is half pre-determined command name and half random words? For example.. Scenario A - I say "Google [Oil Spill]" and I want it to open Google with search results for the term in brackets which could be anything. Scenario B - I say "Locate [Manchester]" and I want it to search for Manchester in Google Maps or anything else non pre-determined I want it to know that 'Google' and 'Locate' are commands and what comes after it are parameters (and could be anything). Question : Does anyone know how to mix the use of pre-determined grammars (words the speech recognition should recognise) and words not in its pre-determined grammar? Code fragments.. using System.Speech.Recognition; ... ... SpeechRecognizer rec = new SpeechRecognizer(); rec.SpeechRecognized += rec_SpeechRecognized; var c = new Choices(); c.Add("search"); var gb = new GrammarBuilder(c); var g = new Grammar(gb); rec.LoadGrammar(g); rec.Enabled = true; ... ... void rec_SpeechRecognized(object sender, SpeechRecognizedEventArgs e) { if (e.Result.Text == "search") { string query = "How can I get a word not defined in Grammar recognised and passed into here!"; launchGoogle(query); } } ... ... private void launchGoogle(string term) { Process.Start("IEXPLORE", "google.com?q=" + term); }

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  • Objective-C protocol vs inheritance vs extending?

    - by ryanjm.mp
    I have a couple classes that have nearly identical code. Only a string or two is different between them. What I would like to do is to make them "x" from another class that defines those functions and then uses constants or something else to define those strings that are different. I'm not sure if "x" is inheritance or extending or what. That is what I need help with. For example: objectA.m: -(void)helloWorld { NSLog("Hello %@",child.name); } objectBob.m: #define name @"Bob" objectJoe.m #define name @"Joe" (I'm not sure if it's legal to define strings, but this gets the point across) It would be ideal if objectBob.m and objectJoe.m didn't have to even define the methods, just their relationship to objectA.m. Is there any way to do something like this? It is kind of like protocol, except in reverse, I want the "protocol" to actually define the functions. If all else fails I'll just make objectA.m: -(void)helloWorld:(NSString *name) { NSLog("Hello %@",name); } And have the other files call that function (and just #import objectA.m).

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  • How to change the direction of wpf marquee dynamically?

    - by ashish semwal
    Hi all, I want to change the direction of my marquee on changeDirection button click. My code for changing direction is : private void changeDirection_click(object sender, RoutedEventArgs e) { if (_marqueeType == MarqueeType.RightToLeft) { _marqueeType = MarqueeType.LeftToRight; StartMarqueeing(_marqueeType); } else if (_marqueeType == MarqueeType.LeftToRight) { _marqueeType = MarqueeType.RightToLeft; StartMarqueeing(_marqueeType); } } And code for start marquee is : public void StartMarqueeing(MarqueeType marqueeType) { double height = canMain.ActualHeight - marqueeList.ActualHeight; marqueeList.Margin = new Thickness(0, 0, 0, 0); doubleAnimation.From = -marqueeList.ActualWidth; doubleAnimation.To = canMain.ActualWidth; doubleAnimation.RepeatBehavior = RepeatBehavior.Forever; doubleAnimation.Duration = new Duration(TimeSpan.FromSeconds(_marqueeTimeInSeconds)); if (marqueeType == MarqueeType.RightToLeft) { Storyboard.SetTargetProperty(doubleAnimation, new PropertyPath("(Canvas.Right)")); _storyBoard.Children.Add(doubleAnimation); _storyBoard.Begin(marqueeList, true); } else if (marqueeType == MarqueeType.LeftToRight) { Storyboard.SetTargetProperty(doubleAnimation, new PropertyPath("(Canvas.Left)")); _storyBoard.Children.Add(doubleAnimation); _storyBoard.Begin(marqueeList, true); } } Now here I am able to change the direction from Right to Left only first time. But when I am change it from Left to Right it’s not changing the marquee position Left to Right. Please help me on this...........its urgent!!!!!!!!!!!

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  • NullPointerException with Servlet

    - by RonaDona
    I am calling a Servlet using its URL address. This is the URL I am typing http://localhost:7001/ryan/olympics?action=selectCatalog&id=1 This is the Servlet's URL for sure; if I change the address I get page not found This is the code for the Servlet. public class Servlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { private static final long serialVersionUID = 1L; public Servlet() { super(); } public void init(ServletConfig config) throws ServletException { System.out.println("*** initializing controller servlet."); super.init(config); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String action = request.getParameter("action"); if (action.equals("selectCatalog")) { String categoryId = request.getParameter("id"); ProductModelDAO dao4 = new ProductModelDAOImpl("jpac"); if (categoryId != null && !categoryId.trim().equals("")) { CategoryDAO dao1 = new CategoryDAOImpl("jpac"); try { Category category = dao1.getCategoryName(categoryId); request.setAttribute("category", category); } catch (Exception e) { e.printStackTrace(); } } try { @SuppressWarnings("unchecked") List<Product> products = dao4 .getProductsByCategory(categoryId); request.setAttribute("products", products); } catch (Exception e) { e.printStackTrace(); } url = "SelectCatalog.jsp"; RequestDispatcher requestDispatcher = getServletContext().getRequestDispatcher(url); requestDispatcher.forward(request, response); I get the NullPointerException pointing to the RequestDispatcher's line. Any help?

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  • Linked list example using threads

    - by Carl_1789
    I have read the following code of using CRITICAL_SECTION when working with multiple threads to grow a linked list. what would be the main() part which uses two threads to add to linked list? #include <windows.h> typedef struct _Node { struct _Node *next; int data; } Node; typedef struct _List { Node *head; CRITICAL_SECTION critical_sec; } List; List *CreateList() { List *pList = (List*)malloc(sizeof(pList)); pList->head = NULL; InitializeCriticalSection(&pList->critical_sec); return pList; } void AddHead(List *pList, Node *node) { EnterCriticalSection(&pList->critical_sec); node->next = pList->head; pList->head = node; LeaveCriticalSection(&pList->critical_sec); } void Insert(List *pList, Node *afterNode, Node *newNode) { EnterCriticalSection(&pList->critical_sec); if (afterNode == NULL) { AddHead(pList, newNode); } else { newNode->next = afterNode->next; afterNode->next = newNode; } LeaveCriticalSection(&pList->critical_sec); } Node *Next(List *pList, Node *node) { Node* next; EnterCriticalSection(&pList->critical_sec); next = node->next; LeaveCriticalSection(&pList->critical_sec); return next; }

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  • Nmock2 and Event Expectations

    - by Kildareflare
    Im in the process of writing a test for a small application that follows the MVP pattern. Technically, I know I should have written the test before the code, but I needed to knock up a demo app quick smart and so im now going back to the test before moving on to the real development. In short I am attempting to test the presenter, however I cannot even get an empty test to run due to an Internal.ExpectationException. The exception is raised on a unexpected invocation of an event assignation. Here is the presenter class, public LBCPresenter(IView view, IModel model) { m_model = model; m_model.BatteryModifiedEvent += new EventHandler(m_model_BatteryModifiedEvent); } Model Interface public interface IModel { event EventHandler BatteryModifiedEvent; } And here is the test class, I can't see what im missing, ive told NMock to expect the event... [TestFixture] public class MVP_PresenterTester { private Mockery mocks; private IView _mockView; private IViewObserver _Presenter; private IModel _mockModel; [SetUp] public void SetUp() { mocks = new Mockery(); _mockView = mocks.NewMock<IView>(); _mockModel = mocks.NewMock<IModel>(); _Presenter = new LBCPresenter(_mockView, _mockModel); } [Test] public void TestClosingFormWhenNotDirty() { Expect.Once.On(_mockModel).EventAdd("BatteryModifiedEvent", NMock2.Is.Anything); //makes no difference if following line is commented out or not //mocks.VerifyAllExpectationsHaveBeenMet(); } } Every time I run the test I get the same expectation Exception. Any ideas?

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  • [C++] Multiple inclusion in multiple files

    - by Amumu
    Hi everyone, I am making a small game. In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTER_H_ #include "Character.h" #endif class BattleRecord { public: Character Attacker; Character Defender; Status status; int DamageDealt; int GoldEarned; int ExpGained; }; In Character.h: #ifndef _EQUIPMENT_H_ #define _EQUIPMENT_H_ #include "Equipment.h" #endif class BattleRecord; class Character { BattleRecord AttackEnemy(Character &Enemy); } In BattleRecord.h: #ifndef _CHARACTER_H_ #define _CHARACTEr_H_ #include "Character.h" #endif #ifndef _BATLE_RECORD_H_ #define _BATLE_RECORD_H_ #include "BattleRecord.h" #endif class GUI { public: //GUI Methods, and two of these: void ViewStats(Character &Player); void Report(BattleRecord Record) } The problem here is, my Character.h and BattleRecord.h need to include each other, and this definitely will cause multiple redefinition problem. Therefore, I used forward declaration in Character.h by adding: class BattleRecord; The problem is sovled. But then, the GUI.h needs BattleRecord.h again for reporting the battle, so I have to include BattleRecord.h into the GUI.h. I also have to include the Character.h in order to pass into the ViewStat function. I got error and stuck with this up to this piont.

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  • How to refresh/redraw the screen (not the program window)

    - by mohrphium
    I'm having a bit of a hard time figuring out, how to remove a drawn ellipse after it has been drawn somewhere else. I need a circle to follow my mouse all the time and this is all the program should do. I get the mousepositions and draw my circle but how can I remove the last one? #include <Windows.h> #include <iostream> void drawRect(int a1, int a2){ HDC screenDC = ::GetDC(0); //Draw circle at mouse position ::Ellipse(screenDC, a1, a2+5, a1+9, a2+14); ::ReleaseDC(0, screenDC); //::InvalidateRect(0, NULL, TRUE); //<- I tried that but then everything flickers //Also, the refresh rate is not fast enough... still some circles left } int main(void) { int a1; int a2; bool exit=false; while (exit!=true) { POINT cursorPos; GetCursorPos(&cursorPos); float x = 0; x = cursorPos.x; float y = 0; y = cursorPos.y; a1=(int)cursorPos.x; a2=(int)cursorPos.y; drawRect(a1, a2); } } I am working with graphics and all that stuff for the first time. Im kinda stuck here... once again. Thanks.

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  • Inorder tree traversal in binary tree in C

    - by srk
    In the below code, I'am creating a binary tree using insert function and trying to display the inserted elements using inorder function which follows the logic of In-order traversal.When I run it, numbers are getting inserted but when I try the inorder function( input 3), the program continues for next input without displaying anything. I guess there might be a logical error.Please help me clear it. Thanks in advance... #include<stdio.h> #include<stdlib.h> int i; typedef struct ll { int data; struct ll *left; struct ll *right; } node; node *root1=NULL; // the root node void insert(node *root,int n) { if(root==NULL) //for the first(root) node { root=(node *)malloc(sizeof(node)); root->data=n; root->right=NULL; root->left=NULL; } else { if(n<(root->data)) { root->left=(node *)malloc(sizeof(node)); insert(root->left,n); } else if(n>(root->data)) { root->right=(node *)malloc(sizeof(node)); insert(root->right,n); } else { root->data=n; } } } void inorder(node *root) { if(root!=NULL) { inorder(root->left); printf("%d ",root->data); inorder(root->right); } } main() { int n,choice=1; while(choice!=0) { printf("Enter choice--- 1 for insert, 3 for inorder and 0 for exit\n"); scanf("%d",&choice); switch(choice) { case 1: printf("Enter number to be inserted\n"); scanf("%d",&n); insert(root1,n); break; case 3: inorder(root1); break; default: break; } } }

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  • Threading.Timer invokes asynchronously many methods

    - by Dimitar
    Hi guys! Please help! I call a threading.timer from global.asax which invokes many methods each of which gets data from different services and writes it to files. My question is how do i make the methods to be invoked on a regular basis let's say 5 mins? What i do is: in Global.asax I declare a timer protected void Application_Start() { TimerCallback timerDelegate = new TimerCallback(myMainMethod); Timer mytimer = new Timer(timerDelegate, null, 0, 300000); Application.Add("timer", mytimer); } the declaration of myMainMethod looks like this: public static void myMainMethod(object obj) { MyDelegateType d1 = new MyDelegateType(getandwriteServiceData1); d1.BeginInvoke(null, null); MyDelegateType d2 = new MyDelegateType(getandwriteServiceData2); d2.BeginInvoke(null, null); } this approach works fine but it invokes myMainMethod every 5 mins. What I need is the method to be invoked 5 mins after all the data is retreaved and written to files on the server. How do I do that?

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  • how can I know current viewcontroller name in iphone

    - by Shikhar
    I have BaseView which implement UIViewController. Every view in project must implement this BaseView. In BaseView, I have method: -(void) checkLoginStatus { defaults = [[NSUserDefaults alloc] init]; if(![[defaults objectForKey:@"USERID"] length] > 0 ) { Login *login=[[Login alloc] initWithNibName:@"Login" bundle:nil]; [self.navigationController pushViewController:login animated:TRUE]; [login release]; } [defaults release]; } The problem is my Login view also implement BaseView, checks for login, and again open LoginView i.e. stuck in to recursive calling. Can I check in checkLoginStatus method if request is from LoginView then take no action else check login. Ex: (void) checkLoginStatus { if(SubView is NOT Login){ defaults = [[NSUserDefaults alloc] init]; if(![[defaults objectForKey:@"USERID"] length] 0 ) { Login *login=[[Login alloc] initWithNibName:@"Login" bundle:nil]; [self.navigationController pushViewController:login animated:TRUE]; [login release]; } [defaults release]; } } Please help..

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