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  • Is this the best approach using generics to check for nulls

    - by user294747
    public static T IsNull<T>(object value, T defaultValue) { turn ((Object.Equals(value,null)) | (Object.Equals(value,DBNull.Value)) ? defaultValue : (T)value); } public static T IsNull<T>(object value) where T :new() { T defaultvalue = new T(); return IsNull(value, defaultvalue); } Have tested, and can use against data objects, classes and variables. Just want to know if there is better way to go about this.

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  • Calling managed code from unmanaged win32 assembly dll - crash

    - by JustGreg
    I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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  • method implementation for this case in Java

    - by Thomas
    Hello, I just saw a code snippet like this: private static class DefaultErrorHandler<RT> implements ErrorHandler<RT> { public RT handle(Object[] params, Throwable e) { return Exceptions.throwUncheckedException(e); } Now I am wondering what the static method "throwUncheckedException (Throwable e)" would return exactly and how it might be implemented regarding the generics. Can anybody give me an example ?

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  • Using CompareTo() on different .NET types (e.g. int vs. double)

    - by Yossin
    Hi, I've got a static method that accepts two object type variables and runs the CompareTo() method: public static int Compare(Object objA, Object objB) { return (((IComparable)objA).CompareTo(objB)); } Problem is that CompareTo() throws an exception when trying to compare between different types (e.g. int and double). Does any one know of a better way in C#, to compare between two different types? Or a workaround to this problem? Thanks

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  • Please , Explain these java code ..?

    - by soma
    I want understand these code before java lab exam especially methode import javax.swing.; import java.util.; import java.text.*; public class EnglishCalendar { public static String[] months = { "January" , "February" , "March", "April" , "May" , "June", "July" , "August" , "September", "October" , "November" , "December" }; public static int days[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; private void showMonth(int m, int y) { int lead_spaces = 0; if (m < 0 || m > 11) { System.out.println("It should be 1 to 12"); } else { System.out.println(); System.out.println(" " + months[m] + " " + y); System.out.println(); GregorianCalendar cal = new GregorianCalendar(y, m, 0); System.out.println("Su Mo Tu We Th Fr Sa "); lead_spaces = cal.get(Calendar.DAY_OF_WEEK); int day_of_month = days[m]; if (cal.isLeapYear(cal.get(Calendar.YEAR)) && m == 1){ day_of_month++;} for (int i = 0; i < lead_spaces; i++) { System.out.print(" "); } for (int i = 1; i <= day_of_month; i++) { if (i < 10) System.out.print(" "); System.out.print(i); if ((lead_spaces + i) % 7 == 0) { System.out.println(); } else { System.out.print(" "); } } System.out.println(); } } private static void doSimpleDateFormat() { Calendar now = Calendar.getInstance(); SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz"); System.out.print(" \n It is now : " + formatter.format(now.getTime())); System.out.println(); } public static void main(String[] args) { String mo = JOptionPane.showInputDialog("Month"); String ye = JOptionPane.showInputDialog("Year"); int mon = new Integer(mo).intValue(); int yea = new Integer(ye).intValue(); EnglishCalendar k = new EnglishCalendar(); k.showMonth(mon - 1 , yea); doSimpleDateFormat(); } }

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  • Can I use an abstract class instead of a private __construct() when creating a singleton in PHP?

    - by Pheter
    When creating a Singleton in PHP, I ensure that it cannot be instantiated by doing the following: class Singleton { private function __construct() {} private function __clone() {} public static function getInstance() {} } However, I realised that defining a class as 'abstract' means that it cannot be instantiated. So is there anything wrong with doing the following instead: abstract class Singleton { public static function getInstance() {} } The second scenario allows me to write fewer lines of code which would be nice. (Not that it actually makes much of a difference.)

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  • Help with simple frame, and graphics in Java

    - by Crystal
    For hw, I'm trying to create a "CustomButton" that has a frame and in that frame, I draw two triangles, and a square over it. It's supposed to give the user the effect of a button press once it is depressed. So for starters, I am trying to set up the beginning graphics, drawing two triangles, and a square. The problem I have is although I set my frame to 200, 200, and the triangles I have drawn I think to the correct ends of my frame size, when I run the program, I have to extend my window to make the whole artwork, my "CustomButton," viewable. Is that normal? Thanks. Code: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class CustomButton { public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { CustomButtonFrame frame = new CustomButtonFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }); } } class CustomButtonFrame extends JFrame { // constructor for CustomButtonFrame public CustomButtonFrame() { setTitle("Custom Button"); setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT); CustomButtonSetup buttonSetup = new CustomButtonSetup(); this.add(buttonSetup); } private static final int DEFAULT_WIDTH = 200; private static final int DEFAULT_HEIGHT = 200; } class CustomButtonSetup extends JComponent { public void paintComponent(Graphics g) { Graphics2D g2 = (Graphics2D) g; // first triangle coords int x[] = new int[TRIANGLE_SIDES]; int y[] = new int[TRIANGLE_SIDES]; x[0] = 0; y[0] = 0; x[1] = 200; y[1] = 0; x[2] = 0; y[2] = 200; Polygon firstTriangle = new Polygon(x, y, TRIANGLE_SIDES); // second triangle coords x[0] = 0; y[0] = 200; x[1] = 200; y[1] = 200; x[2] = 200; y[2] = 0; Polygon secondTriangle = new Polygon(x, y, TRIANGLE_SIDES); g2.drawPolygon(firstTriangle); g2.setColor(Color.WHITE); g2.fillPolygon(firstTriangle); g2.drawPolygon(secondTriangle); g2.setColor(Color.GRAY); g2.fillPolygon(secondTriangle); // draw rectangle 10 pixels off border g2.drawRect(10, 10, 180, 180); } public static final int TRIANGLE_SIDES = 3; }

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  • Retain IEnumerable<T> value during postback

    - by ScG
    I have an IEnumerable< T which is declared on the page like this: IEnumerable< Person person; When the page postsback, the person list is null. How can I retain the values of person list without declaring it as static? Sr. devs in my company say that you should not declare the list as static.

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  • java - find out the type of class which implements of other classes

    - by Johnzzz
    i have a kind of specific problem, let's say, that i have public interface A { } //------------------------------ public class B implements A{ static int countx = 0; } //---------------------------------- public class C implements A{ static int county = 0; } //---------------------------------- public class Arc { public A from; public A to; //======================================== and now I have an object a (which is an instance of Arc) and I want to find out whether it is an instance of B or C and get to the atributes countX or countY (stg like a.from.countX) any ideas? :)

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  • Java array of arry [matrix] of an integer partition with fixed term

    - by user335209
    Hello, for my study purpose I need to build an array of array filled with the partitions of an integer with fixed term. That is given an integer, suppose 10 and given the fixed number of terms, suppose 5 I need to populate an array like this 10 0 0 0 0 9 0 0 0 1 8 0 0 0 2 7 0 0 0 3 ............ 9 0 0 1 0 8 0 0 1 1 ............. 7 0 1 1 0 6 0 1 1 1 ............ ........... 0 6 1 1 1 ............. 0 0 0 0 10 am pretty new to Java and am getting confused with all the for loops. Right now my code can do the partition of the integer but unfortunately it is not with fixed term public class Partition { private static int[] riga; private static void printPartition(int[] p, int n) { for (int i= 0; i < n; i++) System.out.print(p[i]+" "); System.out.println(); } private static void partition(int[] p, int n, int m, int i) { if (n == 0) printPartition(p, i); else for (int k= m; k > 0; k--) { p[i]= k; partition(p, n-k, n-k, i+1); } } public static void main(String[] args) { riga = new int[6]; for(int i = 0; i<riga.length; i++){ riga[i] = 0; } partition(riga, 6, 1, 0); } } the output I get it from is like this: 1 5 1 4 1 1 3 2 1 3 1 1 1 2 3 1 2 2 1 1 2 1 2 1 2 1 1 1 what i'm actually trying to understand how to proceed is to have it with a fixed terms which would be the columns of my array. So, am stuck with trying to get a way to make it less dynamic. Any help?

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  • Not using Web Server for html pages

    - by Manoj
    For an intranet application instead of using a proper web server, it has been planned to just deploy static html pages by sharing it over the network. This static html page is continously updated in the background by a program running on that PC and people access this html page by typing the shared file path directly in the browser. A maximum of 10 simultaneous users are expected to access it. Can any one see the disadvantages or advantages in this type of deployment?

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  • Dictionary w/ null key?

    - by Ralph
    Firstly, why doesn't Dictionary<TKey, TValue> support a single null key? Secondly, is there an existing dictionary-like collection that does? I want to store an "empty" or "missing" or "default" System.Type, thought null would work well for this. More specifically, I've written this class: class Switch { private Dictionary<Type, Action<object>> _dict; public Switch(params KeyValuePair<Type, Action<object>>[] cases) { _dict = new Dictionary<Type, Action<object>>(cases.Length); foreach (var entry in cases) _dict.Add(entry.Key, entry.Value); } public void Execute(object obj) { var type = obj.GetType(); if (_dict.ContainsKey(type)) _dict[type](obj); } public static void Execute(object obj, params KeyValuePair<Type, Action<object>>[] cases) { var type = obj.GetType(); foreach (var entry in cases) { if (entry.Key == null || type.IsAssignableFrom(entry.Key)) { entry.Value(obj); break; } } } public static KeyValuePair<Type, Action<object>> Case<T>(Action action) { return new KeyValuePair<Type, Action<object>>(typeof(T), x => action()); } public static KeyValuePair<Type, Action<object>> Case<T>(Action<T> action) { return new KeyValuePair<Type, Action<object>>(typeof(T), x => action((T)x)); } public static KeyValuePair<Type, Action<object>> Default(Action action) { return new KeyValuePair<Type, Action<object>>(null, x => action()); } } For switching on types. There are two ways to use it: Statically. Just call Switch.Execute(yourObject, Switch.Case<YourType>(x => x.Action())) Precompiled. Create a switch, and then use it later with switchInstance.Execute(yourObject) Works great except when you try to add a default case to the "precompiled" version (null argument exception).

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  • C#, cannot understand this error?

    - by 5YrsLaterDBA
    I am using VS2008. I have a project, SystemSoftware project, connect with a database and we are using L2E. I have a RuntimeInfo class which contains some shared information there. It looks like this: public class RuntimeInfo { public const int PWD_ExpireDays = 30; private static RuntimeInfo thisObj = new RuntimeInfo(); public static string AndeDBConnStr = ConfigurationManager.ConnectionStrings["AndeDBEntities"].ConnectionString; private RuntimeInfo() { } /// <summary> /// /// </summary> /// <returns>Return this singleton object</returns> public static RuntimeInfo getRuntimeInfo() { return thisObj; } } Now I added a helper project, AndeDataViewer, to the solution which creates a simple UI to display data from the database for testing/verification purpose. I don't want to create another set of Entity Data Model in the helper project. I just added all related files as a link in the new helper project. In the AndeDataViewer project, I get the connection string from above RuntimeInfo class which is a class from my SystemSoftware project as a linked file. The code in AndeDataViewer is like this: public class DbAccess : IDisposable { private String connStr = String.Empty; public DbAccess() { connStr = RuntimeInfo.AndeDBConnStr; } } My SystemSoftware works fine that means the RuntimeInfo class has no problem there. But when I run my AndeDataViewer, the statement inside above constructor, connStr = RuntimeInfo.AndeDBConnStr; , throws an exception. The exception is copied here: System.TypeInitializationException was unhandled Message="The type initializer for 'MyCompany.SystemSoftware.SystemInfo.RuntimeInfo' threw an exception." Source="AndeDataViewer" TypeName="MyCompany.SystemSoftware.SystemInfo.RuntimeInfo" StackTrace: at AndeDataViewer.DbAccess..ctor() in C:\workspace\SystemSoftware\Other\AndeDataViewer\AndeDataViewer\DbAccess.cs:line 17 at AndeDataViewer.Window1.rbRawData_Checked(Object sender, RoutedEventArgs e) in C:\workspace\SystemSoftware\Other\AndeDataViewer\AndeDataViewer\Window1.xaml.cs:line 69 at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) .... InnerException: System.NullReferenceException Message="Object reference not set to an instance of an object." Source="AndeDataViewer" StackTrace: at MyCompany.SystemSoftware.SystemInfo.RuntimeInfo..cctor() in C:\workspace\SystemSoftware\SystemSoftware\src\systeminfo\RuntimeInfo.cs:line 24 InnerException: I cannot understand this because it looks fine to me but why there is an exception? we cannot access static variable when a class is a linked class? A linked class should be the same as the local class I think. "Linked" here means when I add file I use "Add As Link".

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  • Is there a straightforward way to have a thread-local instance variable?

    - by Dan Tao
    With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there any straightforward way to declare a class member as thread-local, meaning, each class instance gets an object per thread?

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  • Java : Singleton class instances in a Web based Application

    - by Preethi Jain
    I have this Singleton class inside a Web Application . public class MyDAO { private static MyDAO instance; private MyDAO() { } public static MyDAO getInstance() { if (instance == null) { instance = new MyDAO(); } return instance; } I will access it this way public void get_Data() { MyDAO dao = MyDAO.getInstance(); } How many Objects of MyDAO class will be created if there are 3 Users accessing the Application ?? Will there be one instance of MyDAO per User ??

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  • Why do people run Java GUI's on the Event Queue

    - by asmo
    In Java, to create and show a new JFrame, I simply do this: public static void main(String[] args) { new JFrame().setVisible(true); } However, I have seen many people doing it like this: public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { new JFrame().setVisible(true); } }); } Why? Are there any advantages?

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  • passing Func<TSource, TKey> keySelector error

    - by user338429
    static void Main() { string[] a = { "a", "asd", "bdfsd", "we" }; a = a.OrderBy(fun).ToArray(); } private static int fun(string s) { return s.Length; } its is giving compile time error . I know that we can do this with Lambda expression like this. a.OrderBy(s=>s.Length).ToArray(); but i want to this do by defining different function . What mistake i have done?

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  • How to query a collection of inherited object for a particular object type in grails ?

    - by quilovnic
    Hi, I have a this model : class Question{ Set components static hasMany = [components: QuestionComponent] } class QuestionComponent{ static belongsTo = Question } class QuestionComponentStatus extends QuestionComponent{ } class QuestionComponentOther extends QuestionComponent{ } I want to get only QuestionComponentStatus from Set components : questionInstance.components. ? Thanks a lot

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  • pointer to preallocated memory as an input parameter and have the function fill it

    - by djones2010
    test code: void modify_it(char * mystuff) { char test[7] = "123456"; //last element is null i presume for c style strings here. //static char test[] = "123123"; //when i do this i thought i should be able to gain access to this bit of memory when the function is destroyed but that does not seem to be the case. //char * test = new char[7]; //this is also creating memory on stack and not the heap i reckon and gets destroyed once the function is done with. strcpy_s(mystuff,7,test); //this does the job as long as memory for mystuff has been allocated outside the function. mystuff = test; //this does not work. I know with c style strings you can't just do string assignments they have to be actually copied. in this case I was using this in conjunction with static char test thinking by having it as static the memory would not get destroyed and i can then simply point mystuff to test and be done with it. i would later have address the memory cleanup in the main function. but anyway this never worked. } int main(void) { char * mystuff = new char [7]; //allocate memory on heap where the pointer will point cool(mystuff); std::string test_case(mystuff); std::cout<<test_case.c_str(); //this is the only way i know how to use cout by making it into a string c++ string. delete [] mystuff; return 0; } in the case, of a static array in the function why would it not work. in the case, when i allocated memory using new in the function does it get created on the stack or heap? in the case, i have string which needs to be copied into a char * form. everything i see usually requires const char* instead of just char*. I know i could use reference to take care of this easy. Or char ** to send in the pointer and do it that way. But i just wanted to know if I could do it with just char *. Anyway your thoughts and comments plus any examples would be very helpful.

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  • Function defined but not used in C

    - by thetna
    I have following code: static __inline__ LIST list_List(POINTER P) { return list_Cons(P,list_Nil()); } After compilation I got following warning: inlining is unlikely but function size may grow I removed the inline and changed into the following : static LIST list_List(POINTER P) { return list_Cons(P,list_Nil()); } Now I get the following warning: list_List is defined but not used. Can anybody please suggest me how can remove that warning.

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  • Java overloading and overriding

    - by Padmanabh
    We always say that method overloading is static polymorphism and overriding is runtime polymorphism. What exactly do we mean by static here? Is the call to a method resolved on compiling the code? So whats the difference between normal method call and calling a final method? Which one is linked at compile time?

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