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  • Exception and Inheritance in JAVA

    - by user1759950
    Suppose we have this problem public class Father{ public void method1(){...} } public class Child1 extends Father{ public void method1() throws Exception{ super.method1(); ... } } Child1 extends Father and override method1 but given implementation Child1.method1 now throws a exception, this wont compile as override method can't throw new exceptions. What is the best solution? Propagate the required exception to the Father.. to me this is against encapsulation, inheritance and general OOP ( the father potentially throw and exception that will never happen ) Use a RuntimeException instead? This solution wont propagate the Exception to the father but I read In Oracle docs and others sources states class of exceptions should be used when "Client code cannot do anything" this is not that case, this exception will b useful to recover blablabla ( why is wrong to use RuntimeException instead? ) Other.. thanks, Federico

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  • How can one enforce calling a base class function after derived class constructor?

    - by Mike Elkins
    I'm looking for a clean C++ idiom for the following situation: class SomeLibraryClass { public: SomeLibraryClass() { /* start initialization */ } void addFoo() { /* we are a collection of foos */ } void funcToCallAfterAllAddFoos() { /* Making sure this is called is the issue */ } }; class SomeUserClass : public SomeLibraryClass { public: SomeUserClass() { addFoo(); addFoo(); addFoo(); // SomeUserClass has three foos. } }; class SomeUserDerrivedClass : public SomeUserClass { public: SomeUserDerrivedClass() { addFoo(); // This one has four foos. } }; So, what I really want is for SomeLibraryClass to enforce the calling of funcToCallAfterAllAddFoos at the end of the construction process. The user can't put it at the end of SomeUserClass::SomeUserClass(), that would mess up SomeUserDerrivedClass. If he puts it at the end of SomeUserDerrivedClass, then it never gets called for SomeUserClass. To further clarify what I need, imagine that /* start initialization */ acquires a lock, and funcToCallAfterAllAddFoos() releases a lock. The compiler knows when all the initializations for an object are done, but can I get at that information by some nice trick?

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  • How to prevent Firefox from putting shadows around input boxes which have had their background colou

    - by Andrew
    Hi there, I'm creating a set of input fields and using javascript's .style.backgroundColor = "red" to change the colour of any invalid fields. In Chrome, there is no problem. However, in Firefox, as soon as I touch the backgroundColor (even if I set it to white) then I get these strange shadow effects. Does anyone know what's going on? before: http://imgur.com/xYRLT.png after: http://imgur.com/R1tdI.png

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  • c# error when using the Database.cs files

    - by Kumu
    Inconsistent accessibility: parameter type 'FoolballLeague.FootballLeagueDatabase' is less accessible than method 'FoolballLeague.MainMenu.MainMenu(FoolballLeague.FootballLeagueDatabase)' C:\Users\achini\Desktop\FootballLeague\FootballLeague\MainMenu.cs I have got this error when I insert this part to the code //public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) //{ //InitializeComponent(); //footballLeagueDatabase = footballLeagueDatabaseIn; //} The whole code of the first part is as following, But I dont know what do I need to do to sort out this error. public partial class MainMenu : Form { FootballLeagueDatabase footballLeagueDatabase; Game game; Login login; public MainMenu() { InitializeComponent(); changePanel(1); } //public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) //{ //InitializeComponent(); //footballLeagueDatabase = footballLeagueDatabaseIn; //} If you have any idea please let me know, I need this part to the system.

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  • no longer an issue

    - by MrTemp
    I am still new to c# and wpf This program is a clock with different view and I would like to use the context menu to change between view, but the error says that there is no definition or extension method for the events. Right now I have the event I'm working on popping up a MessageBox just so I know it has run, but I cannot get it to compile. public partial class MainWindow : NavigationWindow { public MainWindow() { //InitializeComponent(); } public void AnalogMenu_Click(object sender, RoutedEventArgs e) { /*AnalogClock analog = new AnalogClock(); this.NavigationService.Navigate(analog);*/ } public void DigitalMenu_Click(object sender, RoutedEventArgs e) { MessageBox.Show("Digital Clicked"); /*DigitalClock digital = new DigitalClock(); this.NavigationService.Navigate(digital);*/ } public void BinaryMenu_Click(object sender, RoutedEventArgs e) { /*BinaryClock binary = new BinaryClock(); this.NavigationService.Navigate(binary);*/ } } and the xaml call if you want it <NavigationWindow.ContextMenu> <ContextMenu Name="ClockMenu" > <MenuItem Name="ToAnalog" Header="To Analog" ToolTip="Changes to an analog clock"/> <MenuItem Name="ToDigital" Header="To Digital" ToolTip="Changes to a digital clock" Click="DigitalMenu_Click" /> <MenuItem Name="ToBinary" Header="To Binary" ToolTip="Changes to a binary clock"/> </ContextMenu> </NavigationWindow.ContextMenu>

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  • How to write curiously recurring templates with more than 2 layers of inheritance?

    - by Kyle
    All the material I've read on Curiously Recurring Template Pattern seems to one layer of inheritance, ie Base and Derived : Base<Derived>. What if I want to take it one step further? #include <iostream> using std::cout; template<typename LowestDerivedClass> class A { public: LowestDerivedClass& get() { return *static_cast<LowestDerivedClass*>(this); } void print() { cout << "A\n"; } }; template<typename LowestDerivedClass> class B : public A<LowestDerivedClass> { public: void print() { cout << "B\n"; } }; class C : public B<C> { public: void print() { cout << "C\n"; } }; int main() { C c; c.get().print(); // B b; // Intentionally bad syntax, // b.get().print(); // to demonstrate what I'm trying to accomplish return 0; } How can I rewrite this code to compile without errors (and output "C\nB\n")?

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  • Ngen or compile to native code is better

    - by Raghav55
    I want to know which is one better native code generated is NGen.exe is better or run time conversion of IL to native code by JIT ? using System; public class Vehicle { public Vehicle() { } public string Name { get; set; } public string Model { get; set; } } class Program { static void Main(string[] args) { Vehicle aVech = new Vehicle(); aVech.Name = "BUS"; aVech.Model = "1980"; } }

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  • How do I find out if an object can be Invoke()'d?

    - by Jurily
    Consider the following class: public class Event<T> { public delegate void Handler<t>(t msg); private event Handler<T> E; public void connect(Delegate handler) { E += delegate(T msg) { object target = handler.Target; if (Invokable(target) { target.BeginInvoke(handler, new object[] { msg }); } }; } public void emit(T msg) { if ( E != null ) { E(msg); } } private static bool Invokable(object o) { // magic } } How do I implement Invokable(), and what else do I need for this code to compile?

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  • Request/Response pattern in SOA implementation

    - by UserControl
    In some enterprise-like project (.NET, WCF) i saw that all service contracts accept a single Request parameter and always return Response: [DataContract] public class CustomerRequest : RequestBase { [DataMember] public long Id { get; set; } } [DataContract] public class CustomerResponse : ResponseBase { [DataMember] public CustomerInfo Customer { get; set; } } where RequestBase/ResponseBase contain common stuff like ErrorCode, Context, etc. Bodies of both service methods and proxies are wrapped in try/catch, so the only way to check for errors is looking at ResponseBase.ErrorCode (which is enumeration). I want to know how this technique is called and why it's better compared to passing what's needed as method parameters and using standard WCF context passing/faults mechanisms?

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  • Rails multi level model security

    - by rballz
    I have the need to do the following in Rails to mirror a desktop application: a User and an Office 'owns' a record, if you don't own the record on a user or office level you're kicked into the public realm. user gets read,write,delete to the model record office gets read/write/delete to the model record other or public gets read/write/delete to the model record e.g. UserA owns a model record with read/write/delete OfficeA owns a model with read/write other/public gets read I was wondering if a plugin/gem existed to grant this functionality?

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  • how to create property of type generic class?

    - by Anish
    public class SelectionList<T> : ObservableCollection<SelectionItem<T>> where T : IComparable<T> { // Code } public class SelectionItem<T> : INotifyPropertyChanged { // Code } I need to create a property which is of the type SelectionList...as follows: public SelectionList<string> Sports { get; set; }. But when I replace string with DataRowView, as public SelectionList<DataRowView> Sports { get; set; }. I am getting error. Please help

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  • Extract information from a Func<bool, T> or alike lambda

    - by Syska
    I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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  • Need help: input int from console and pass it into method in different class

    - by christophe
    i'm a beginner, Need help, Please!!! I want to read number "a" from console and then store them in variable to use as passing to a different class (different .java file). How do i code the 2 classes? thanks public class PassedInMethod{ private int a; . public PAssMethod(int a) { a = a; // TODO: where to get the a? System.out.println("a was passed in!"+a); } public class Mainclass{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); int a; System.out.print( "Enter your nember: " ); a = input.nextInt(); PassedInMethod(int a); }

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  • jQuery AutoComplete with three levels of suggestions?

    - by Meitham
    I am building a django based application and its time to add the DHTML stuff. One of my fields represent a database field with this format databaseName.tableName.fieldName I would like to have javascript autocompletion in three levels, say once I type part of the database names I get a list of all matching databases, one that is selected I get a list of all tables, and once that is selected I get a list of all fields in that table, all in the same textfield. Any help would be appreciated. Thanks M

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  • Statically Init a derived class

    - by AC
    With c++, Is there a way to get a derived class to inherit its own static initializer? I am trying to do something like the following: class Base { public: class StaticInit { public: virtual StaticInit() =0; }; }; class Derived: public Base { public: virtual StaticInit::StaticInit() { //do something with the derived class } static StaticInit init; } static Derived::StaticInit init; it would also be nice if I didn't have to define the init var in each derived class. I am currently redefining the StaticInit internal class in each derived class but it seems redundant. Each derived class is a singleton, and I need the instance to be stored in a lookup table at program startup.

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  • Casting Class into String and Vice Versa in JAVA

    - by topgun_ivard
    I have a program in which I need to store a Class object into memory by casting it into String. Is it possible to convert the String back into the original Class so that I can use that class variables? I am doing this in JAVA. Example: test.java class hello{ public String h1; public String h2; } public class test { public static void main(String[] args) { hello h = new hello(); h.h1 = "hello"; h.h2 = "world"; String s = h.toString(); System.out.println("Print s : "+s); // Now I need to convert String s into type hello so that // I can do this: // (hello)s.h1; // (hello)s.h2; } } NOTE: this is not a homework, this is a personal project and I would be grateful if anyone can help! Thanks! Ivar

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  • Can anyone tell me were I am making mistake in the snippet

    - by Solitaire
    public partial class Form1 : Form { [DllImport("coredll.dll")] static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong); const int GWL_WNDPROC = -4; public delegate int WindProc(IntPtr hWnd, uint msg, long Wparam, long lparam); public Form1() { InitializeComponent(); WindProc SampleProc = new WindProc (SubclassWndProc); SetWindowLong(this .Handle , GWL_WNDPROC, SampleProc.Method .MethodHandle.Value.ToInt32()); } public int SubclassWndProc(IntPtr hwnd, uint msg, long Wparam, long lparam) { return 1; } Here is the sample which i was trying to take the window procedure of a form, this is how i do in C++ i get the windwproc easlily if i try the same in C# .net 3.5 i am unable to get the window proc,, after calling SetWindowLong API application hangs and it pops up some dont send report... i have read this is the way to get the window proc.. please let me know were i am making mistake...

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  • Play! 1.2.5 with mongodb | Model Validation not happening

    - by TGV
    I have a simple User model whose fields are annotated with play validation annotations and morphia annotations like below. import play.data.validation.*; import play.modules.morphia.Model; import com.google.code.morphia.annotations.*; @Entity public class User extends Model{ @Id @Indexed(name="USERID", unique=true) public ObjectId userId; @Required public String userName; @Email @Indexed(name="USEREMAIL", unique=true) @Required public String userEmail; } Now I have a service which has a CreateNewUser method responsible for persisting the data. I have used Morphia plugin for the dao support. But the problem is that User Document gets persisted in mongo-db even if userName or userEmail is NULL. Also @Email validation does not happen // Below code is in app/controllers/Application.java User a = new User(); a.userName = "user1"; // calling bean to create user, userService is in app/service/UserService userService.createNewUser(a); It does not work even after adding @valid and validation.hasErrors() check.Below code is in app/service/UserService public void createNewUser(@Valid User user) { if (Validation.hasErrors()) { System.out.println("has errors"); } else { // TODO Auto-generated method stub userDao.save(user); } }

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  • How does ambigous methods are resolved in java ?

    - by Jijoy
    Hi , I do have a question. package org.study.algos; public class Study { public static void main(String[] args) { A a = new A(); a.m1(null); } } class A { public void m1(String s) { System.out.println("String"); System.out.println(s); } public void m1(Object obj) { System.out.println("Object"); System.out.println(obj); } } Here , the output is String null Why JVM resolve the method to one with String arguement ? Thanks in advance J

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  • C# specifying generic delegate type param at runtime

    - by smerlin
    following setup, i have several generic functions, and i need to choose the type and the function identified by two strings at runtime. my first try looked like this: public static class FOOBAR { public delegate void MyDelegateType(int param); public static void foo<T>(int param){...} public static void bar<T>(int param){...} public static void someMethod(string methodstr, string typestr) { MyDelegateType mydel; Type mytype; switch(typestr) { case "int": mytype = typeof(int); break; case "double": mytype = typeof(double); break; default: throw new InvalidTypeException(typestr); } switch(methodstr) { case "foo": mydel = foo<mytype>; //error break; case "bar": mydel = bar<mytype>; //error break; default: throw new InvalidTypeException(methodstr); } for(int i=0; i<1000; ++i) mydel(i); } } since this didnt work, i nested those switchs (a methodstr switch inside the typestr switch or viceversa), but that solution is really ugly and unmaintainable. The number of types is pretty much fixed, but the number of functions like foo or bar will increase by high numbers, so i dont want nested switchs. So how can i make this working without using nested switchs ?

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  • Android: Unable to access a local website over HTTPS

    - by user1253789
    I am trying to access a locally hosted website and get its HTML source to parse. I have few questions: 1) Can I use "https://An IP ADDRESS HERE" as a valid URL to try and access. I do not want to make changes in the /etc/hosts file so I want to do it this way. 2) I cannot get the html, since it is giving me Handshake exceptions and Certificate issues. I have tried a lot of help available over the web , but am not successful. Here is the code I am using: public class MainActivity extends Activity { private TextView textView; String response = ""; String finalresponse=""; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textView = (TextView) findViewById(R.id.TextView01); System.setProperty("javax.net.ssl.trustStore","C:\\User\\*" ); System.setProperty("javax.net.ssl.trustStorePassword", "" ); } private class DownloadWebPageTask extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... urls) { TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() { public java.security.cert.X509Certificate[] getAcceptedIssuers() { return null; } public void checkClientTrusted(java.security.cert.X509Certificate[] certs, String authType) { } public void checkServerTrusted(java.security.cert.X509Certificate[] certs, String authType) { } } }; try { SSLContext sc = SSLContext.getInstance("SSL"); sc.init(null, trustAllCerts, new java.security.SecureRandom()); HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory()); } catch (Exception e) { } try { URL url = new URL("https://172.27.224.133"); HttpsURLConnection con =(HttpsURLConnection)url.openConnection(); con.setHostnameVerifier(new AllowAllHostnameVerifier()); finalresponse=readStream(con.getInputStream()); } catch (Exception e) { e.printStackTrace(); } return finalresponse; } private String readStream(InputStream in) { BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader(in)); String line = ""; while ((line = reader.readLine()) != null) { response+=line; } } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } } return response; } @Override protected void onPostExecute(String result) { textView.setText(finalresponse); } } public void readWebpage(View view) { DownloadWebPageTask task = new DownloadWebPageTask(); task.execute(new String[] { "https://172.27.224.133" }); } }

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  • Java Inheritance Concept Understanding

    - by Nirmal
    Hello All.... I am just refreshing the oops features of the java. So, I have a little confusion regarding inheritance concept. For that I have a following sample code : class Super{ int index = 5; public void printVal(){ System.out.println("Super"); } } class Sub extends Super{ int index = 2; public void printVal(){ System.out.println("Sub"); } } public class Runner { public static void main(String args[]){ Super sup = new Sub(); System.out.println(sup.index+","); sup.printVal(); } } Now above code is giving me output as : 5,Sub. Here, we are overriding printVal() method, so that is understandable that it is accessing child class method only. But I could not understand why it's accessing the value of x from Super class... Thanks in advance....

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