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• virtual methods and template classes

  - by soxs060389

  Hi I got over a problem, I think a very specific one. I've got 2 classes, a B aseclass and a D erived class (from B aseclass). B is a template class ( or class template) and has a pure virtual method virutal void work(const T &dummy) = 0; The D erived class is supposed to reimplement this, but as D is Derived from B rather than D being another template class, the compiler spits at me that virtual functions and templates don't work at once. Any ideas how to acomplish what I want? I am thankfull for any thoughts and Ideas, especially if you allready worked out that problem this class is fixed aka AS IS, I can not edit this without breaking existing code base template <typename T> class B { public: ... virtual void work(const T &dummy) = 0; .. }; take int* as an example class D : public B<int*>{ ... virtual void work(const int* &dummy){ /* put work code here */ } .. }; Edit: The compiler tells me, that void B<T>::work(const T&) [with T = int*] is pure virtual within D

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• Is this a correct way to stop Execution Task

  - by Yan Cheng CHEOK

  I came across code to stop execution's task. private final ExecutorService executor = Executors.newSingleThreadExecutor(); public void stop() { executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (!Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; } I realize that, it is possible for Runnable to be in forever loop, as Unknown fun may Thread.sleep, clear the interrupt flag and ignore the InterruptedException Unknown fun may Thread.interrupted, clear the interrupt flag. I was wondering, is the following way correct way to fix the code? private final ExecutorService executor = Executors.newSingleThreadExecutor(); private volatile boolean flag = true; public void stop() { flag = false; executor.shutdownNow(); try { executor.awaitTermination(100, TimeUnit.DAYS); } catch (InterruptedException ex) { log.error(null, ex); } } public Runnable getRunnable() { return new Runnable() { public void run() { while (flag && !Thread.currentThread().isInterrupted()) { // What if inside fun(), someone try to clear the interrupt flag? // Say, through Thread.interrupted(). We will stuck in this loop // forever. fun(); } } }; }

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• Java NullPointerException In the constructor's class

  - by AndreaF

  I have made a Java class where I have defined a constructor and some methods but I get a NullPointer Exception, and I don't know how I could fix It. public class Job { String idJob; int time; int timeRun; Job j1; List<Job> startBeforeStart; List<Job> restricted; Job(String idJob, int time){ this.idJob=idJob; this.time=time; } public boolean isRestricted() { return restricted.size() != 0; } public void startsBeforeStartOf(Job job){ startBeforeStart.add(job); job.restricted.add(this); } public void startsAfterStartOf(Job job){ job.startsBeforeStartOf(this); } public void checkRestrictions(){ if (!isRestricted()){ System.out.println("+\n"); } else{ Iterator<Job> itR = restricted.iterator(); while(itR.hasNext()){ Job j1 = itR.next(); if(time>timeRun){ System.out.println("-\n"); time--; } else { restricted.remove(j1); } } } } @Override public boolean equals(Object obj) { return obj instanceof Job && ((Job) obj).idJob.equals(idJob); } public void run() { timeRun++; } } PS Looking in a forum a user says that to fix the error I should make an ArrayList inside the constructor (without modify the received parameters that should remain String id and int time), but I haven't understand what He mean.

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• Splitting a C++ class into files now won't compile.

  - by vgm64

  Hi. I am teaching myself to write classes in C++ but can't seem to get the compilation to go through. If you can help me figure out not just how, but why, it would be greatly appreciated. Thank you in advance! Here are my three files: make_pmt.C #include <iostream> #include "pmt.h" using namespace std; int main() { CPMT *pmt = new CPMT; pmt->SetVoltage(900); pmt->SetGain(2e6); double voltage = pmt->GetVoltage(); double gain= pmt->GetGain(); cout << "The voltage is " << voltage << " and the gain is " << gain << "." <<endl; return 0; } pmt.C #include "pmt.h" using namespace std; class CPMT { double gain, voltage; public: double GetGain() {return gain;} double GetVoltage() {return voltage;} void SetGain(double g) {gain=g;} void SetVoltage(double v) {voltage=v;} }; pmt.h #ifndef PMT_H #define PMT_H 1 using namespace std; class CPMT { double gain, voltage; public: double GetGain(); double GetVoltage(); void SetGain(double g); void SetVoltage(double v); }; #endif And for reference, I get a linker error (right?): Undefined symbols: "CPMT::GetVoltage()", referenced from: _main in ccoYuMbH.o "CPMT::GetGain()", referenced from: _main in ccoYuMbH.o "CPMT::SetVoltage(double)", referenced from: _main in ccoYuMbH.o "CPMT::SetGain(double)", referenced from: _main in ccoYuMbH.o ld: symbol(s) not found collect2: ld returned 1 exit status

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• Trying to make a plugin system in C++

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• UserControl/TreeView Problem....Not getting result during runtime..

  - by Samiul

  Hi all, My problem is, I'm using a TreeView in a UserControl. While debugging, I can see the results are adding in the TreeView but it's not happening when I'm using that UserControl onto my MainForm. The UserControl containing the TreeView remains blank during runtime of the main application. I've also referenced the UserControl project with my Main project. Here I'm giving my code for helping me out. Thanks in advance. Code: In the UserControl class: public override void Refresh() { PopulateTreeView(); } private void PopulateTreeView() { TreeNodeCollection treeNodeCollection; treeNodeCollection = CreateParentNode("My Information"); CreateChildNode(treeNodeCollection, "Name"); CreateChildNode(treeNodeCollection, "Address"); this.Update(); myTreeView.ExpandAll(); } private TreeNodeCollection CreateParentNode(string parentNode) { TreeNode treeNode = new TreeNode(parentNode); myTreeView.Nodes.Add(treeNode); return treeNode.Nodes; } private void CreateChildNode(TreeNodeCollection nodeCollection, string itemName) { TreeNode treeNode = new TreeNode(itemName); nodeCollection.Add(treeNode); } In my MainForm: private void button1_Click(object sender, EventArgs e) { UserControl userControl = new UserControl(); userControl.Refresh(); }

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• passing data from an activity to an listactivity or listview

  - by wicked14

  need help on passing data from an activity to an listactivity or listview for an android app. im having problems on passing data to a listview. what the app do is from addact class the user can input things to do and in the viewact class this will display the activies add by the user in listview public class addact extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.newact); Button btn1 = (Button)findViewById(R.id.btnsave); final EditText et1 = (EditText)findViewById(R.id.etactivity); btn1.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { Intent it = new Intent(addact.this, viewact.class); it.putExtra("thekey", et1.getText().toString()); startActivity(it); } }); } } public class viewact extends ListActivity { String addToDo =getIntent().getExtras().getString("thekey"); String[] toDoAct = new String[] {addToDo }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.viewact); setListAdapter(new ArrayAdapter<String>(this, R.layout.viewact,toDoAct)); ListView listView = getListView(); listView.setTextFilterEnabled(true); listView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { for (int i=0; i < 2; i++) { Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_LONG).show(); } } }); } }

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• push(ing)_back objects pointers within a loop

  - by Jose Manuel Albornoz

  Consider the following: I have a class CDevices containing, amongst others, a string member class CDevice { public: CDevice(void); ~CDevice(void); // device name std::string Device_Name; etc... } and somewhere else in my code I define another class that contains a vector of pointers to CDevices class CDevice; class CServers { public: CServers(void); ~CServers(void); // Devices vector vector<CDevice*> Devices; etc... } The problem appears in the following lines in my main.c pDevice = new CDevice; pDevice->Device_Name = "de"; Devices.push_back(pDevice); pDevice->Device_Name = " revolotiunibus"; Devices.push_back(pDevice); pDevice->Device_Name = " orbium"; Devices.push_back(pDevice); pDevice->Device_Name = " coelestium"; Devices.push_back(pDevice); for(int i = 0; i < (int)Devices.size(); ++i) cout << "\nLoad name = " << Devices.at(i)->Device_Name << endl; The output I get is " coelestium" repeated four times: each time I push_back a new element into the vector all of the already existing elements take the value of the one which has just been added. I have also tried using iterators to recover each element in the vector with the same results. Could someone please tell me what's wrong here? Thankx

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• Constructor Overload Problem in C++ Inherrentance

  - by metdos

  Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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• c# winforms events restore textbox contents on escape

  - by aj3jr

  Using c# in 2008 Express. I have a textbox containing a path. I append a "\" at the end on Leave Event. If the user presses 'Escape' key I want the old contents to be restored. When I type over all the text and press 'Escape' I hear a thump and the old text isn't restored. Here what I have so far ... public string _path; public string _oldPath; this.txtPath.KeyPress += new System.Windows.Forms.KeyPressEventHandler(txtPath_CheckKeys); this.txtPath.Enter +=new EventHandler(txtPath_Enter); this.txtPath.LostFocus += new EventHandler(txtPath_LostFocus); public void txtPath_CheckKeys(object sender, KeyPressEventArgs kpe) { if (kpe.KeyChar == (char)27) { _path = _oldPath; } } public void txtPath_Enter(object sender, EventArgs e) { //AppendSlash(sender, e); _oldPath = _path; } void txtPath_LostFocus(object sender, EventArgs e) { //throw new NotImplementedException(); AppendSlash(sender, e); } public void AppendSlash(object sender, EventArgs e) { //add a slash to the end of the txtPath string on ANY change except a restore this.txtPath.Text += @"\"; } Thanks in advance,

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• iPhone --- 3DES Encryption returns "wrong" results?

  - by Jan Gressmann

  Hello fellow developers, I have some serious trouble with a CommonCrypto function. There are two existing applications for BlackBerry and Windows Mobile, both use Triple-DES encryption with ECB mode for data exchange. On either the encrypted results are the same. Now I want to implent the 3DES encryption into our iPhone application, so I went straight for CommonCrypto: http://www.opensource.apple.com/source/CommonCrypto/CommonCrypto-32207/CommonCrypto/CommonCryptor.h I get some results if I use CBC mode, but they do not correspond with the results of Java or C#. Anyway, I want to use ECB mode, but I don't get this working at all - there is a parameter error showing up... This is my call for the ECB mode... I stripped it a little bit: const void *vplainText; plainTextBufferSize = [@"Hello World!" length]; bufferPtrSize = (plainTextBufferSize + kCCBlockSize3DES) & ~(kCCBlockSize3DES - 1); plainText = (const void *) [@"Hello World!" UTF8String]; NSString *key = @"abcdeabcdeabcdeabcdeabcd"; ccStatus = CCCrypt(kCCEncrypt, kCCAlgorithm3DES, kCCOptionECBMode, key, kCCKeySize3DES, nil, // iv, not used with ECB plainText, plainTextBufferSize, (void *)bufferPtr, // output bufferPtrSize, &movedBytes); t is more or less the code from here: http://discussions.apple.com/thread.jspa?messageID=9017515 But as already mentioned, I get a parameter error each time... When I use kCCOptionPKCS7Padding instead of kCCOptionECBMode and set the same initialization vector in C# and my iPhone code, the iPhone gives me different results. Is there a mistake by getting my output from the bufferPtr? Currently I get the encrypted stuff this way: NSData *myData = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)movedBytes]; result = [[NSString alloc] initWithData:myData encoding:NSISOLatin1StringEncoding]; It seems I almost tried every setting twice, different encodings and so on... where is my error?

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• Thread Locking CollectionViewSource

  - by Robert

  I added an event handler to my code and it broke all access to the CollectionViewSources in the SystemHTA class saying "The calling thread cannot access this object because a different thread owns it". My class was working when "this.systemHTA = new SystemHTA();" was placed outside of the DeviceManager_StateChanged() function. public partial class MainWindow : Window { private DeviceManager DeviceManager = DeviceManager.Instance; public SystemHTA systemHTA; public MainWindow() { InitializeComponent(); } private void Window_Loaded(object sender, RoutedEventArgs e) { DeviceManager.StateChanged += new EventHandler<DeviceManagerStateChangedEventArgs>(DeviceManager_StateChanged); DeviceManager.Initialize(); } void DeviceManager_StateChanged(object sender, DeviceManagerStateChangedEventArgs e) { if (e.State == DeviceManagerState.Operational) { this.systemHTA = new SystemHTA(); } } private void button1_Click(object sender, RoutedEventArgs e) { this.systemHTA.GetViewSourceTest(); } } public class SystemHTA { private CollectionViewSource _deviceTestSource; public SystemHTA() { _deviceTestSource = new CollectionViewSource(); _deviceTestSource.Source = CreateLoadData<HWController>.ControllerCollection; } public void GetViewSourceTest() { ListCollectionView view = (ListCollectionView)_deviceTestSource.View; //This creates an error saying a thread already owns _deviceTestSource } }

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• Flash AS3: How to Make scroll bar react to dynamic textfield movement?

  - by HeroicNate

  I've been looking for a tutorial and answer to this for a while but can't find what I'm looking for. I am loading html text into a dynamic textfield, and I have a scrollbar controlling the scroll using the code below. What I want to do is also add scroll up/down buttons and have the scroll bar move in relation to the text scroll. I was just going to use "tracklistingtext.scrollV -- " for the scroll buttons, but right now the scroll bar doesn't recognize the text movement. What do I need to do to get the scroll bar to listen to the text scroll position? var listTextreq:URLRequest=new URLRequest("tracklist.txt"); var listTextLoader:URLLoader = new URLLoader(); var bounds:Rectangle=new Rectangle(scrollMC.x,scrollMC.y,0,300); var scrolling:Boolean=false; function fileLoaded(event:Event):void { tracklistingtext.htmlText=listTextLoader.data; tracklistingtext.multiline=true; tracklistingtext.wordWrap=true; scrollMC.addEventListener(MouseEvent.MOUSE_DOWN, startScroll); stage.addEventListener(MouseEvent.MOUSE_UP, stopScroll); addEventListener (Event.ENTER_FRAME, enterHandler); } listTextLoader.addEventListener(Event.COMPLETE, fileLoaded); listTextLoader.load(listTextreq); function startScroll(e:Event):void { scrolling=true; scrollMC.startDrag(false,bounds); } function stopScroll(e:Event):void { scrolling=false; scrollMC.stopDrag(); } function enterHandler (e:Event):void { if (scrolling == true) { tracklistingtext.scrollV = Math.round(((scrollMC.y - bounds.y)/300)*tracklistingtext.maxScrollV); } } Any help is greatly appreciated.

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• Open closed prinicple, problem

  - by Marcus

  Hi, I'm trying to apply OCP to a code snippet I have that in it's current state is really smelly, but I feel I'm not getting all the way to the end. Current code: public abstract class SomeObject {} public class SpecificObject1 : SomeObject {} public class SpecificObject2 : SomeObject {} // Smelly code public class Model { public void Store(SomeObject someObject) { if (someObject is SpecificObject1) {} else if (someObject is SpecificObject2) {} } } That is really ugly, my new approach looks like this: // No so smelly code public class Model { public void Store(SomeObject someObject) { throw new Expception("Not allowed!"); } public void Store(SpecificObject1 someObject) {} public void Store(SpecificObject2 someObject) {} } When a new SomeObject type comes along I must implement how that specific object is stored, this will break OCP cause I need to alter the Model-class. To move the store logic to SomeObject also feels wrong cause then I will violate SRP (?), becuase in this case the SomeObject is almost like a DTO, it's resposibility it not how to know to store itself. If a new implementation to SomeObject comes along who's store implementation is missing I will get a runtime error due to exception in Store method in Model class, it also feels like a code smell. This is because calling code will in the form of IEnumerable<SomeObject> sequence; I will not know the specific types of the sequence objects. I can't seem to grasp the OCP-concept. Anyone has any concrete examples or links that is a bit more than just some Car/Fruit example?

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• What would be a better implementation of shared variable among subclass

  - by Churk

  So currently I have a spring unit testing application. And it requires me to get a session cookie from a foreign authentication source. Problem what that is, this authentication process is fairly expensive and time consuming, and I am trying to create a structure where I am authenticate once, by any subclass, and any subsequent subclass is created, it will reuse this session cookie without hitting the authentication process again. My problem right now is, the static cookie is null each time another subclass is created. And I been reading that using static as a global variable is a bad idea, but I couldn't think of another way to do this because of Spring framework setting things during run time and how I would set the cookie so that all other classes can use it. Another piece of information. The variable is being use, but is change able during run time. It is not a single user being signed in and used across the board. But more like a Sub1 would call login, and we have a cookie. Then multiple test will be using that login until SubX will come in and say, I am using different credential, so I need to login as something else. And repeats. Here is a outline of my code: public class Parent implements InitializingBean { protected static String BASE_URL; public static Cookie cookie; ... All default InitializingBean methods ... afterPropertiesSet() { cookie = // login process returns a cookie } } public class Sub1 extends Parent { @resource public String baseURL; @PostConstruct public void init() { // set parents with my baseURL; BASE_URL = baseURL; } public void doSomething() { // Do something with cookie, because it should have been set by parent class } } public class Sub2 extends Parent { @resource public String baseURL; @PostConstruct public void init() { // set parents with my baseURL; BASE_URL = baseURL; } public void doSomethingElse() { // Do something with cookie, because it should have been set by parent class } }

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• problem with kCFSocketReadCallBack

  - by zp26

  Hello. I have a problem with my program. I created a socket with "kCFSocketReadCallBack. My intention was to call the "acceptCallback" only when it receives a string to the socket. Instead my program does not just accept the connection always goes into "startReceive" stop doing so and sometimes crash the program. Can anybody help? Thanks readSocket = CFSocketCreateWithNative( NULL, fd, kCFSocketReadCallBack, AcceptCallback, &context ); static void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) // Called by CFSocket when someone connects to our listening socket. // This implementation just bounces the request up to Objective-C. { ServerVistaController * obj; #pragma unused(address) // assert(address == NULL); assert(data != NULL); obj = (ServerVistaController *) info; assert(obj != nil); #pragma unused(s) assert(s == obj->listeningSocket); if (type & kCFSocketAcceptCallBack){ [obj acceptConnection:*(int *)data]; } if (type & kCFSocketAcceptCallBack){ [obj startReceive:*(int *)data]; } } -(void)startReceive:(int)fd { CFReadStreamRef readStream = NULL; CFIndex bytes; UInt8 buffer[MAXLENGTH]; CFStreamCreatePairWithSocket( kCFAllocatorDefault, fd, &readStream, NULL); if(!readStream){ close(fd); [self updateLabel:@"No readStream"]; } CFReadStreamOpen(readStream); [self updateLabel:@"OpenStream"]; bytes = CFReadStreamRead( readStream, buffer, sizeof(buffer)); if (bytes < 0) { [self updateLabel:(NSString*)buffer]; close(fd); } CFReadStreamClose(readStream); }

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• About calling an subclass' overriding method when casted to its superclass

  - by Omega

  #include <iostream> class Vehicle { public: void greet() { std::cout << "Hello, I'm a vehicle"; } }; class Car : public Vehicle { public: void greet() { std::cout << "Hello, I'm a car"; } }; class Bike : public Vehicle { public: void greet() { std::cout << "Hello, I'm a bike"; } }; void receiveVehicle(Vehicle vehicle) { vehicle.greet(); } int main() { receiveVehicle(Car()); return 0; } As you can see, I'm trying to send a parameter of type Vehicle to a function, which calls greet(). Car and Bike are subclasses of Vehicle. They overwrite greet(). However, I'm getting "Hello, I'm a vehicle". I suppose that this is because receiveVehicle receives a parameter of type Vehicle instead of a specific subclass like Car or Bike. But that's what I want: I want this function to work with any subclass of Vehicle. Why am I not getting the expected output?

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• Apply [ThreadStatic] attribute to a method in external assembly

  - by Sen Jacob

  Can I use an external assembly's static method like [ThreadStatic] method? Here is my situation. The assembly class (which I do not have access to its source) has this structure public class RegistrationManager() { private RegistrationManager() {} public static void RegisterConfiguration(int ID) {} public static object DoWork() {} public static void UnregisterConfiguration(int ID) {} } Once registered, I cannot call the DoWork() with a different ID without unregistering the previously registered one. Actually I want to call the DoWork() method with different IDs simultaneously with multi-threading. If the RegisterConfiguration(int ID) method was [ThreadStatic], I could have call it in different threads without problems with calls, right? So, can I apply the [ThreadStatic] attribute to this method or is there any other way I can call the two static methods same time without waiting for other thread to unregister it? If I check it like the following, it should work. for(int i=0; i < 10; i++) { new Thread(new ThreadStart(() => Checker(i))).Start(); } public string Checker(int i) { public static void RegisterConfiguration(i); // Now i cannot register second time public static object DoWork(i); Thread.Sleep(5000); // DoWork() may take a little while to complete before unregistered public static void UnregisterConfiguration(i); }

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• How to check at runtime if a class implements certain interface?

  - by mare

  Let's say I have some content classes like Page, TabGroup, Tab, etc. Certain of those will be implementing my IWidgetContainer interface - it means they will geet an additional field named ContainedItems from the interface and some methods for manipulating this field. Now I need to reflect the fact that some class implements this interface by rendering out some special custom controls in my ASP.NET MVC Views (like jQuery Add/Remove/Move/Reorder buttons). For instance, TabGroup will implement IWidgetContainer because it will contain tabs but a tab will not implement it because it won't have the ability to contain anything. So I have to somehow check in my view, when I render my content objects (The problem is, I use my base class as strong type in my view not concrete classes), whether it implements IWidgetContainer. How is that possible or have I completely missed something? To rephrase the question, how do you reflect some special properties of a class (like interface implementation) in the UI in general (not necessarily ASP.NET MVC)? Here's my code so far: [DataContract] public class ContentClass { [DataMember] public string Slug; [DataMember] public string Title; [DataMember] protected ContentType Type; } [DataContract] public class Group : ContentClass, IWidgetContainer { public Group() { Type = ContentType.TabGroup; } public ContentList ContainedItems { get; set; } public void AddContent(ContentListItem toAdd) { throw new NotImplementedException(); } public void RemoveContent(ContentListItem toRemove) { throw new NotImplementedException(); } } [DataContract] public class GroupElement : ContentClass { public GroupElement() { Type = ContentType.Tab; } } Interface: interface IWidgetContainer { [DataMember] ContentList ContainedItems { get; set; } void AddContent(ContentListItem toAdd); void RemoveContent(ContentListItem toRemove); }

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• search a listview in Persian

  - by user3641353

  I have listview with textview which I use textview for search items in listview. It works true but just in English. I can not change the keyboard to Persian. Do you have any solution? this is my code: ArrayAdapter<String> adapter; String[] allMovesStr = {"??? ???? ????","?? ???? ????","?? ???? ????? ???????"}; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.all_moves); adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, allMovesStr); setListAdapter(adapter); EditText ed = (EditText) findViewById(R.id.inputSearch); ListView lv = (ListView) findViewById(android.R.id.list); lv.setTextFilterEnabled(true); ed.addTextChangedListener(new TextWatcher() { public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } public void afterTextChanged(Editable arg0) { // vaghti kar bar harfi vared kard josteju mikone : AllMoves.this.adapter.getFilter().filter(arg0); } }); }

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• java - question about thread abortion and deadlock - volatile keyword

  - by Tiyoal

  Hello all, I am having some troubles to understand how I have to stop a running thread. I'll try to explain it by example. Assume the following class: public class MyThread extends Thread { protected volatile boolean running = true; public void run() { while (running) { synchronized (someObject) { while (someObject.someCondition() == false && running) { try { someObject.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } // do something useful with someObject } } } public void halt() { running = false; interrupt(); } } Assume the thread is running and the following statement is evaluated to true: while (someObject.someCondition() == false && running) Then, another thread calls MyThread.halt(). Eventhough this function sets 'running' to false (which is a volatile boolean) and interrupts the thread, the following statement is still executed: someObject.wait(); We have a deadlock. The thread will never be halted. Then I came up with this, but I am not sure if it is correct: public class MyThread extends Thread { protected volatile boolean running = true; public void run() { while (running) { synchronized (someObject) { while (someObject.someCondition() == false && running) { try { someObject.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } // do something useful with someObject } } } public void halt() { running = false; synchronized(someObject) { interrupt(); } } } Is this correct? Is this the most common way to do this? This seems like an obvious question, but I fail to come up with a solution. Thanks a lot for your help.

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• A member variable's hashCode() value is different

  - by Jacques René Mesrine

  There's a piece of code that looks like this. The problem is that during bootup, 2 initialization takes place. (1) Some method does a reflection on ForumRepository & performs a newInstance() purely to invoke #setCacheEngine. (2) Another method following that invokes #start(). I am noticing that the hashCode of the #cache member variable is different sometimes in some weird scenarios. Since only 1 piece of code invokes #setCacheEngine, how can the hashCode change during runtime (I am assuming that a different instance will have a different hashCode). Is there a bug here somewhere ? public class ForumRepository implements Cacheable { private static CacheEngine cache; private static ForumRepository instance; public void setCacheEngine(CacheEngine engine) { cache = engine; } public synchronized static void start() { instance = new ForumRepository(); } public synchronized static void addForum( ... ) { cache.add( .. ); System.out.println( cache.hashCode() ); // snipped } public synchronized static void getForum( ... ) { ... cache.get( .. ); System.out.println( cache.hashCode() ); // snipped } }

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• Factorial function - design and test.

  - by lukas

  I'm trying to nail down some interview questions, so I stared with a simple one. Design the factorial function. This function is a leaf (no dependencies - easly testable), so I made it static inside the helper class. public static class MathHelper { public static int Factorial(int n) { Debug.Assert(n >= 0); if (n < 0) { throw new ArgumentException("n cannot be lower that 0"); } Debug.Assert(n <= 12); if (n > 12) { throw new OverflowException("Overflow occurs above 12 factorial"); } //by definition if (n == 0) { return 1; } int factorialOfN = 1; for (int i = 1; i <= n; ++i) { //checked //{ factorialOfN *= i; //} } return factorialOfN; } } Testing: [TestMethod] [ExpectedException(typeof(OverflowException))] public void Overflow() { int temp = FactorialHelper.MathHelper.Factorial(40); } [TestMethod] public void ZeroTest() { int factorialOfZero = FactorialHelper.MathHelper.Factorial(0); Assert.AreEqual(1, factorialOfZero); } [TestMethod] public void FactorialOf5() { int factOf5 = FactorialHelper.MathHelper.Factorial(5); Assert.AreEqual(120,factOf5); } [TestMethod] [ExpectedException(typeof(ArgumentException))] public void NegativeTest() { int factOfMinus5 = FactorialHelper.MathHelper.Factorial(-5); } I have a few questions: Is it correct? (I hope so ;) ) Does it throw right exceptions? Should I use checked context or this trick ( n 12 ) is ok? Is it better to use uint istead of checking for negative values? Future improving: Overload for long, decimal, BigInteger or maybe generic method? Thank you

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• WPF bound object update notification

  - by Carlo

  I have a TreeView with a few objects bound to it, let's say something like this: public class House { public List<Room> Rooms { get; set; } public List<Person> People { get; set; } public House() { this.Rooms = new List<Room>(); this.People = new List<Person>(); } public void BuildRoom(string name) { this.Rooms.Add(new Room() { Name = name }); } public void DestroyRoom(string name) { this.Rooms.Remove(new Room() { Name = name }); } public void PersonEnter(string name) { this.People.Add(new Person() { Name = name }); } public void PersonLeave(string name) { this.People.Remove(new Person() { Name = name }); } } public class Room { public string Name { get; set; } } public class Person { public string Name { get; set; } } The TreeView is watching over the House object, whenever a room is built / destroyed or a person enters / leaves, my tree view updates itself to show the new state of the house (I omitted some implementation details for simplicity). What I want is to know the exact moment when this update finishes, so I can do something right there, the thing is that I created an indicator of the selected item, and when something moves, I need to update said indicator's position, that's the reason I need it exactly when the tree view updates. Let me know if you know a solution to this. Also, the code is not perfect (DestroyRoom and PersonLeave), but you get the idea. Thanks!

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• how to find by date from timestamp column in JPA criteria

  - by Kre Toni

  I want to find a record by date. In entity and database table datatype is timestamp. I used Oracle database. @Entity public class Request implements Serializable { @Id private String id; @Version private long version; @Temporal(TemporalType.TIMESTAMP) @Column(name = "CREATION_DATE") private Date creationDate; public Request() { } public Request(String id, Date creationDate) { setId(id); setCreationDate(creationDate); } public String getId() { return id; } public void setId(String id) { this.id = id; } public long getVersion() { return version; } public void setVersion(long version) { this.version = version; } public Date getCreationDate() { return creationDate; } public void setCreationDate(Date creationDate) { this.creationDate = creationDate; } } in mian method public static void main(String[] args) { RequestTestCase requestTestCase = new RequestTestCase(); EntityManager em = Persistence.createEntityManagerFactory("Criteria").createEntityManager(); em.getTransaction().begin(); em.persist(new Request("005",new Date())); em.getTransaction().commit(); Query q = em.createQuery("SELECT r FROM Request r WHERE r.creationDate = :creationDate",Request.class); q.setParameter("creationDate",new GregorianCalendar(2012,12,5).getTime()); Request r = (Request)q.getSingleResult(); System.out.println(r.getCreationDate()); } in oracle database record is ID CREATION_DATE VERSION 006 05-DEC-12 05.34.39.200000 PM 1 Exception is Exception in thread "main" javax.persistence.NoResultException: getSingleResult() did not retrieve any entities. at org.eclipse.persistence.internal.jpa.EJBQueryImpl.throwNoResultException(EJBQueryImpl.java:1246) at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:750) at com.ktrsn.RequestTestCase.main(RequestTestCase.java:29)

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