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  • Why doesn't HashTable.Contains() just simply return false if it is passed a null?

    - by Nate Pinchot
    I understand why passing a null to HashTable.Contains() doesn't work, but I don't understand what the point of it throwing an ArgumentNullException is - instead of just simply returning false? What is the benefit of throwing the exception (other than to make me do null checks before calling .Contains())? Caused By [System.ArgumentNullException] Key cannot be null. Parameter name: key at System.Collections.Hashtable.ContainsKey(Object key) at System.Collections.Hashtable.Contains(Object key)

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  • Is my code a correct implementation of insertion sort?

    - by user1657171
    This code sorts correctly. Is this an insertion sort? import java.util.Scanner; public class InsertionSort { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter the number of elements: "); int count; count = sc.nextInt(); int[] a = new int[count]; System.out.println("Enter elements: "); for(int i = 0 ; i<count;i++){ a[i] = sc.nextInt(); } int j,temp; System.out.println("aftr insertion sort :"); for(int i = 1 ; i<count;i++){ j=i; while(j>0 && a[j-1] > a[j] ){ temp = a[j]; a[j] = a[j-1]; a[j-1] = temp; j--; } } for(int i = 0 ; i<count;i++){ System.out.print(a[i]+" "); } } }

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  • Java Instance of: Supertypes and Subtypes seem to be equal? How to test exactly for Type?

    - by jens
    I need to test, if an instance is exactly of a given type. But it seems that instanceof returns true also if the subtype is tested for the supertype (case 3). I never knew this before and I am quite surprised. Am I doing something wrong here? How do I exactly test for a given type? //.. class DataSourceEmailAttachment extends EmailAttachment //... EmailAttachment emailAttachment = new EmailAttachment(); DataSourceEmailAttachment emailAttachmentDS = new DataSourceEmailAttachment(); if (emailAttachment instanceof EmailAttachment){ System.out.println(" 1"); } if (emailAttachment instanceof DataSourceEmailAttachment){ System.out.println(" 2"); } if (emailAttachmentDS instanceof EmailAttachment){ System.out.println(" 3 "); } if (emailAttachmentDS instanceof DataSourceEmailAttachment){ System.out.println(" 4"); } RESULT: 1 3 4 I want to avoid case 3, I only want "exact matches" (case 1 and 4) how do I test for them?

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  • what is the difference between static class and normal class?

    - by Phsika
    when i prefer static or normal class? Or what is the difference between them? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace staticmethodlar { class Program { static void Main(string[] args) { SinifA.method1(); } } static class SinifA { public static void method1() { Console.WriteLine("Deneme1"); } } public static class SinifB { public static void method2() { Console.WriteLine("Deneme2"); } } public class sinifC { public void method3() { Console.WriteLine("Deneme3"); } } public class sinifD : sinifC { void method4() { Console.WriteLine("Deneme4"); } sinifC sinifc = new sinifC(); // i need to use it:) } }

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  • get greatest prime factor in F#

    - by Alex
    I had VS 11 beta and the following code was working without problem: let rec fac x y = if (x = y) then y elif (x % y = 0I) then fac (x / y) y else fac x / (y + 1I);; Now I installed VS 2012 RC and I get the following error: The type 'System.Numerics.BigInteger -> System.Numerics.BigInteger' is not compatible with the type 'System.Numerics.BigInteger' Is code not correct or F# interactive? It's F# 3.0.

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  • How to override [Authorize] attribute in the MVC Web API?

    - by NullReference
    I have a MVC Web Api Controller that uses the [Authorize] attribute at the class level. This makes all of the api methods require authorization but I'd like to create an attribute called [ApiPublic] that overrides the [Authorize] attribute. There is a similar technique described here for normal MVC controllers. I tried creating an AuthorizeAttribute based of the System.Web.Http.AuthorizeAttribute but none of the overridden events are called if I put it on a api method that has the [Authorize] at the class level. Anyone have an idea how to override the authorize for the web api? [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class ApiPublicAttribute : AuthorizeAttribute { protected override void HandleUnauthorizedRequest(System.Web.Http.Controllers.HttpActionContext actionContext) { base.HandleUnauthorizedRequest(actionContext); } public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext) { base.OnAuthorization(actionContext); } protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext) { return true; } }

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  • Why should Java ThreadLocal variables be static

    - by kellyfj
    I was reading that JavaDoc for Threadlocal here http://java.sun.com/j2se/1.5.0/docs/api/java/lang/ThreadLocal.html and it says "ThreadLocal instances are typically private static fields in classes that wish to associate state with a thread (e.g., a user ID or Transaction ID). " But my question is why did they choose to make it static (typically) - it makes it a bit confusing to have "per thread" state but its static?

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  • Is it guaranteed that new Integer(i) == i in Java?

    - by polygenelubricants
    Consider the following snippet: int i = 99999999; byte b = 99; short s = 9999; Integer ii = Integer.valueOf(9); // should be within cache System.out.println(new Integer(i) == i); // "true" System.out.println(new Integer(b) == b); // "true" System.out.println(new Integer(s) == s); // "true" System.out.println(new Integer(ii) == ii); // "false" It's obvious why the last line will ALWAYS prints "false": we're using == reference identity comparison, and a new object will NEVER be == to an already existing object. The question is about the first 3 lines: are those comparisons guaranteed to be on the primitive int, with the Integer auto-unboxed? Are there cases where the primitive would be auto-boxed instead, and reference identity comparisons are performed? (which would all then be false!)

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  • .NET: Start a thread as suspended

    - by Ikaso
    In unmanaged code you can create a thread in suspended state. In .NET Framework I can't find this option. Is it because the Thread constructor puts the thread in a suspended state? Is there other reasons why this is not supported?

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  • Client/Server app

    - by Knowing me knowing you
    Guys could anyone tell me what's wrong am I doing here? Below are four files Client, main, Server, main. I'm getting an error on Client side after trying to fromServer.readLine(). Error: Error in Client Software caused connection abort: recv failed package client; import java.io.*; import java.net.*; import java.util.Scanner; public class Client { private PrintWriter toServer; private BufferedReader fromServer; private Socket socket; public Client( )throws IOException { socket = new Socket("127.0.0.1",3000); } public void openStreams() throws IOException { // // InputStream is = socket.getInputStream(); // OutputStream os = socket.getOutputStream(); // fromServer = new BufferedReader(new InputStreamReader(is)); // toServer = new PrintWriter(os, true); toServer = new PrintWriter(socket.getOutputStream(),true); fromServer = new BufferedReader(new InputStreamReader(socket.getInputStream())); } public void closeStreams() throws IOException { fromServer.close(); toServer.close(); socket.close(); } public void run()throws IOException { openStreams(); String msg = ""; Scanner scanner = new Scanner(System.in); toServer.println("Hello from Client."); // msg = scanner.nextLine(); while (msg != "exit") { System.out.println(">"); // msg = scanner.nextLine(); toServer.println("msg"); String tmp = fromServer.readLine(); System.out.println("Server said: " + tmp); } closeStreams(); } } package server; import java.net.*; import java.io.*; public class Server { private ServerSocket serverSocket; private Socket socket; private PrintWriter toClient; private BufferedReader fromClient; public void run() throws IOException { System.out.println("Server is waiting for connections..."); while (true) { openStreams(); processClient(); closeStreams(); } } public void openStreams() throws IOException { serverSocket = new ServerSocket(3000); socket = serverSocket.accept(); toClient = new PrintWriter(socket.getOutputStream(),true); fromClient = new BufferedReader(new InputStreamReader(socket.getInputStream())); } public void closeStreams() throws IOException { fromClient.close(); toClient.close(); socket.close(); serverSocket.close(); } public void processClient()throws IOException { System.out.println("Connection established."); String msg = fromClient.readLine(); toClient.println("Client said " + msg); } } package client; import java.io.IOException; public class Main { /** * @param args the command line arguments */ public static void main(String[] args) { // TODO code application logic here try { Client client = new Client(); client.run(); } catch(IOException e) { System.err.println("Error in Client " + e.getMessage()); } } } package server; import java.io.IOException; public class Main { /** * @param args the command line arguments */ public static void main(String[] args) { // TODO code application logic here Server server = new Server(); try { server.run(); } catch(IOException e) { System.err.println("Error in Server " + e.getMessage()); } } }

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  • getting bordering US states (php)

    - by Peter Ehrlich
    HI need to be able to select a state and be given a list of the bordering states. Does anyone have or know of code already done for this? If I have to write it myself, what would be the best way - possibly a mysql database of borders (two state columns for each row), and then select matching?

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  • Zend_Registry: real life examples

    - by takeshin
    Do you find Zend_Registry useful? For which tasks it should be used? For which not? Global state for variables is not a good practice. Main objects may have global state injected via $front->setParam('paramName', $object), so what's the purpose of Zend_Registry?.

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  • What compliance and legal clearances are required to use Google MAP API with Iphone Apps?

    - by Sak
    We are using 2 following google services, we need to talk to google folks if we need to do some additional stuff to fulfill the conditions: Reverse Geocoding APIs: For getting city and state from the iphone's geocodes (latitudes and longitudes) Doing a Local Business Search: based on city and state Also is it mandatory to embade Google maps with iphone apps while using these Google Maps APS?:

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  • About NullPointer Exception in Arraylist

    - by user2234456
    List<PrcSubList> listSl = new ArrayList<PrcSubList>(); if (listSl == null || listSl.size() == 0) { PrcSubList subListAdd=coreService.addSubListByAddAlert(childSub); System.out.println("sublist after insert db :" + subListAdd.getName()); listSl.add(subListAdd); System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); } Ouput with first System.out.println("sublist after insert db :" + subListAdd.getName()); sublist after insert db :SYSTEM_ALERT_12312313 Problem But i have NullPointerException with 2nd System.out.println(listSl.size() +" sublist after insert list:" + listSl.get(0).getName()); Can you help me!

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  • How decide whether a e-mail was newly sent, replied or forwarded?

    - by user572783
    I use Visual Studio 2010 to create an Outlook 2007 Addin. Now i want to know whether a e-mail was newly sent, replied or forwarded. Is there any property for this? using Outlook = Microsoft.Office.Interop.Outlook; namespace _Outlook2k7_Add_In { public partial class ThisAddIn { private void ThisAddIn_Startup(object sender, System.EventArgs e) { } private void ThisAddIn_Shutdown(object sender, System.EventArgs e) { } void Application_ItemSend(object Item, ref bool Cancel) { Outlook.MailItem mail = Item as Outlook.MailItem; if (mail == null) return; // Magic? } #region VSTO generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InternalStartup() { this.Startup += new System.EventHandler(ThisAddIn_Startup); this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown); this.Application.ItemSend += new Outlook.ApplicationEvents_11_ItemSendEventHandler(Application_ItemSend); } #endregion } }

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  • Doesn't get the output in Java Database Connectivity

    - by Dooree
    I'm working on Java Database Connectivity through Eclipse IDE. I built a database through Ubuntu Terminal, and I need to connect and work with it. However, when I tried to run the following code, I don't get any error, but the following output is showed, anybody knows why I don't get the output from the code ? //STEP 1. Import required packages import java.sql.*; public class FirstExample { // JDBC driver name and database URL static final String JDBC_DRIVER = "com.mysql.jdbc.Driver"; static final String DB_URL = "jdbc:mysql://localhost/EMP"; // Database credentials static final String USER = "username"; static final String PASS = "password"; public static void main(String[] args) { Connection conn = null; Statement stmt = null; try{ //STEP 2: Register JDBC driver Class.forName("com.mysql.jdbc.Driver"); //STEP 3: Open a connection System.out.println("Connecting to database..."); conn = DriverManager.getConnection(DB_URL,USER,PASS); //STEP 4: Execute a query System.out.println("Creating statement..."); stmt = conn.createStatement(); String sql; sql = "SELECT id, first, last, age FROM Employees"; ResultSet rs = stmt.executeQuery(sql); //STEP 5: Extract data from result set while(rs.next()){ //Retrieve by column name int id = rs.getInt("id"); int age = rs.getInt("age"); String first = rs.getString("first"); String last = rs.getString("last"); //Display values System.out.print("ID: " + id); System.out.print(", Age: " + age); System.out.print(", First: " + first); System.out.println(", Last: " + last); } //STEP 6: Clean-up environment rs.close(); stmt.close(); conn.close(); }catch(SQLException se){ //Handle errors for JDBC se.printStackTrace(); }catch(Exception e){ //Handle errors for Class.forName e.printStackTrace(); }finally{ //finally block used to close resources try{ if(stmt!=null) stmt.close(); }catch(SQLException se2){ }// nothing we can do try{ if(conn!=null) conn.close(); }catch(SQLException se){ se.printStackTrace(); }//end finally try }//end try System.out.println("Goodbye!"); }//end main }//end FirstExample <ConnectionProperties> <PropertyCategory name="Connection/Authentication"> <Property name="user" required="No" default="" sortOrder="-2147483647" since="all"> The user to connect as </Property> <Property name="password" required="No" default="" sortOrder="-2147483646" since="all"> The password to use when connecting </Property> <Property name="socketFactory" required="No" default="com.mysql.jdbc.StandardSocketFactory" sortOrder="4" since="3.0.3"> The name of the class that the driver should use for creating socket connections to the server. This class must implement the interface 'com.mysql.jdbc.SocketFactory' and have public no-args constructor. </Property> <Property name="connectTimeout" required="No" default="0" sortOrder="9" since="3.0.1"> Timeout for socket connect (in milliseconds), with 0 being no timeout. Only works on JDK-1.4 or newer. Defaults to '0'. </Property> ...

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  • Several C# Language Questions

    - by Water Cooler v2
    1) What is int? Is it any different from the struct System.Int32? I understand that the former is a C# alias (typedef or #define equivalant) for the CLR type System.Int32. Is this understanding correct? 2) When we say: IComparable x = 10; Is that like saying: IComparable x = new System.Int32(); But we can't new a struct, right? or in C like syntax: struct System.In32 *x; x=>someThing = 10; 3) What is String with a capitalized S? I see in Reflector that it is the sealed String class, which, of course, is a reference type, unlike the System.Int32 above, which is a value type. What is string, with an uncapitalized s, though? Is that also the C# alias for this class? Why can I not see the alias definitions in Reflector? 4) Try to follow me down this subtle train of thought, if you please. We know that a storage location of a particular type can only access properties and members on its interface. That means: Person p = new Customer(); p.Name = "Water Cooler v2"; // legal because as Name is defined on Person. but // illegal without an explicit cast even though the backing // store is a Customer, the storage location is of type // Person, which doesn't support the member/method being // accessed/called. p.GetTotalValueOfOrdersMade(); Now, with that inference, consider this scenario: int i = 10; // obvious System.object defines no member to // store an integer value or any other value in. // So, my question really is, when the integer is // boxed, what is the *type* it is actually boxed to. // In other words, what is the type that forms the // backing store on the heap, for this operation? object x = i; Update Thank you for your answers, Eric Gunnerson and Aaronought. I'm afraid I haven't been able to articulate my questions well enough to attract very satisfying answers. The trouble is, I do know the answers to my questions on the surface, and I am, by no means, a newbie programmer. But I have to admit, a deeper understanding to the intricacies of how a language and its underlying platform/runtime handle storage of types has eluded me for as long as I've been a programmer, even though I write correct code.

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  • Generic Dictionary - Getting Convertion Error

    - by pm_2
    The following code is giving me an error: // GetDirectoryList() returns Dictionary<string, DirectoryInfo> Dictionary<string, DirectoryInfo> myDirectoryList = GetDirectoryList(); // The following line gives a compile error foreach (Dictionary<string, DirectoryInfo> eachItem in myDirectoryList) The error it gives is as follows: Cannot convert type 'System.Collections.Generic.KeyValuePair<string,System.IO.DirectoryInfo>' to 'System.Collections.Generic.Dictionary<string,System.IO.DirectoryInfo>’ My question is: why is it trying to perform this conversion? Can I not use a foreach loop on this type of object?

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  • How to test Guice Singleton?

    - by 01
    Guice Singletons are weird for me First I thought that IService ser = Guice.createInjector().getInstance(IService.class); System.out.println("ser=" + ser); ser = Guice.createInjector().getInstance(IService.class); System.out.println("ser=" + ser); will work as singleton, but it returns ser=Service2@1975b59 ser=Service2@1f934ad its ok, it doesnt have to be easy. Injector injector = Guice.createInjector(); IService ser = injector.getInstance(IService.class); System.out.println("ser=" + ser); ser = injector.getInstance(IService.class); System.out.println("ser=" + ser); works as singleton ser=Service2@1975b59 ser=Service2@1975b59 So i need to have static field with Injector(Singleton for Singletons) how do i pass to it Module for testing?

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  • When to use new layouts and when to use new activities?

    - by cmdfrg
    I'm making a game in Android and I'm trying to add a set of menu screens. Each screen takes up the whole display and has various transitions available to other screens. As a rough summary, the menu screens are: Start screen Difficult select screen Game screen. Pause screen. Game over screen. And there are several different ways you can transition between screen: 1 - 2 2 - 3 3 - 4 (pause game) 4 - 1 (exit game) 4 - 3 (resume game) 3 - 5 (game ends) Obviously, I need some stored state when moving between screens, such as the difficulty level select when starting a game and what the player's score is when the game over screen is shown. Can anyone give me some advice for the easiest way to implement the above screens and transitions in Android? All the create/destroy/pause/resume methods make me nervous about writing brittle code if I'm not careful. I'm not fond of using an Activity for each screen. It seems too heavy weight, having to pass data around using intents seems like a real pain and each screen isn't a useful module by itself. As the "back" button doesn't always go back to the previous screen either, my menu layout doesn't seem to fit the activity model well. At the moment, I'm representing each screen as an XML layout file and I have one activity. I set the different buttons on each layout to call setContentView to update the screen the main activity is showing (e.g. the pause button changes the layout to the pause screen). The activity holds onto all the state needed (e.g. the current difficulty level and the game high score), which makes it easy to share data between screens. This seems roughly similar to the LunarLander sample, except I'm using multiple screens. Does what I have at the moment sound OK or am I not doing things the typical Android way? Is there a class I can use (e.g. something like ViewFlipper) that could make my life easier? By the way, my game screen is implemented as a SurfaceView that stores the game state. I need the state in this view to persist between calls to setContentView (e.g. to resume from paused). Is the right idea to create the game view when the activity starts, keep a reference to it and then use this reference with setContentView whenever I want the game screen to appear?

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  • How to check if String value is Boolean type in Java?

    - by Ragnar
    I did a little search on this but couldn't find anything useful. The point being that if String value is either "true" or "false" the return value should be true. In every other value it should be false. I tried these: String value = "false"; System.out.println("test1: " + Boolean.parseBoolean(value)); System.out.println("test2: " + Boolean.valueOf(value)); System.out.println("test3: " + Boolean.getBoolean(value)); All functions returned false :(

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  • The time-to-reach-queue has elapsed

    - by nieve
    I'm attempting to send a message to a remote private queue from an error queue with powershell. The code I use looks like this: $msg = $src_q.Peek() $msg.Label = GetLabelWithoutFailedQueue($msg) $msg.UseDeadLetterQueue = $true $msg.UseTracing = $true $msg.AcknowledgeType = [System.Messaging.AcknowledgeTypes]::NegativeReceive $msg.TimeToBeReceived = [System.TimeSpan]::FromSeconds(10) $msg.TimeToReachQueue = [System.TimeSpan]::FromSeconds(10) $tx = new-object System.Messaging.MessageQueueTransaction $tx.Begin() $dest_q.Send($msg, $tx) $tx.Commit() The message keeps on appearing on the transactional dead letter queue with the class: "The time-to-reach-queue has elapsed." Anyone's got any idea what could trigger such an error? The queue definitely exists- I do manage to peek it. Also, the reason I get the message from the error queue by peeking is just for testing purposes; I have tried doing the same thing with Receive and the result is the same.

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  • Show WindowsForm in the center of the Screen (Dual Screen)

    - by serhio
    I have Dual Monitors and want displaying a windows form in the center of the screen. (I have a variable MonitorId=0 or 1). I have: System.Windows.Forms.Screen[] allScreens=System.Windows.Forms.Screen.AllScreens; System.Windows.Forms.Screen myScreen = allScreens[0]; int screenId = RegistryManager.ScreenId; // DualScreen management if (screenId > 0) { // Possede 2-ieme ecran if (allScreens.Length == 2) { if (screenId == 1) myScreen = allScreens[0]; else myScreen = allScreens[1]; } } this.Location = new System.Drawing.Point(myScreen.Bounds.Left, 0); this.StartPosition = FormStartPosition.CenterScreen;

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  • How does IIS persist a user's identity from page to page?

    - by Rising Star
    Web pages are, by nature, state-less objects. When you click from page to page in an ASP.net application, each request for a page is treated as a brand-new request. We use things like cookies, session-variables, and query strings to maintain state from page to page. When you log in to an ASP.net web application using Windows Authentication, how does IIS persist your identity between pages?

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  • program to determine number of duplicates in a sentence

    - by bhavna raghuvanshi
    public class duplicate { public static void main(String[] args)throws IOException { System.out.println("Enter words separated by spaces ('.' to quit):"); Set<String> s = new HashSet<String>(); Scanner input = new Scanner(System.in); while (true) { String token = input.next(); if (".".equals(token)) break; if (!s.add(token)) System.out.println("Duplicate detected: " + token); } System.out.println(s.size() + " distinct words:\n" + s); } } my program detects and prints duplicate words but i need to print the number of duplicate words also. pls help me do it.

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