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  • Why can final object be modified?

    - by Matt McCormick
    I came across the following code in a code base I am working on: public final class ConfigurationService { private static final ConfigurationService INSTANCE = new ConfigurationService(); private List providers; private ConfigurationService() { providers = new ArrayList(); } public static void addProvider(ConfigurationProvider provider) { INSTANCE.providers.add(provider); } ... INSTANCE is declared as final. Why can objects be added to INSTANCE? Shouldn't that invalidate the use of final. (It doesn't). I'm assuming the answer has to do something with pointers and memory but would like to know for sure.

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  • Java OutOfMemoryError strange behaviour

    - by Evgeniy Dorofeev
    Assuming we have a max memory of 256M, why does this code work: public static void main(String... args) { for (int i = 0; i < 2; i++) { byte[] a1 = new byte[150000000]; } byte[] a2 = new byte[150000000]; } but this one throw an OOME? public static void main(String... args) { //for (int i = 0; i < 2; i++) { byte[] a1 = new byte[150000000]; } byte[] a2 = new byte[150000000]; }

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  • END_TAG exception while calling WCF WebService from Android using KSOAP2?

    - by sunil
    Hi, I am trying to call a WCF Web Service from Android using KSOAP2 library. But I am getting this END_TAG exception. I have followed this thread to call WCF Web Service but still no result. I am passing "urn:TestingWcf/GetNames" as SOAP_ACTION, does this causes problem in Android since the error occurs at the statement "aht.call(SOAP_ACTION, envelope)" where aht is AndroidHttpTransport class object. Can someone let me know what the problem may be? import org.ksoap2.*; import org.ksoap2.serialization.*; import org.ksoap2.transport.*; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class Ksoap2Test extends Activity { private static final String METHOD_NAME = "GetNamesJsonWithParam" private static final String NAMESPACE = "http://tempuri.org/"; private static final String URL = "http://192.168.3.61/BattleEmpire.Service/TestingWcf.svc/basic"; final String SOAP_ACTION = "urn:TestingWcf/GetNamesJsonWithParam"; TextView tv; StringBuilder sb; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); tv = new TextView(this); sb = new StringBuilder(); call(); tv.setText(sb.toString()); setContentView(tv); } public void call() { try { SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME); request.addProperty("imran", "Qing"); SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11); envelope.dotNet = true; envelope.setOutputSoapObject(request); System.out.println("Request " + envelope.toString()); //HttpTransportSE androidHttpTransport = new HttpTransportSE(URL); AndroidHttpTransport aht = new AndroidHttpTransport(URL); aht.call(SOAP_ACTION, envelope); //aht.debug = true; /*HttpTransportSE androidHttpTransport = new HttpTransportSE(URL); androidHttpTransport.call(SOAP_ACTION, envelope);*/ SoapPrimitive result = (SoapPrimitive)envelope.getResponse(); //to get the data String resultData = result.toString(); // 0 is the first object of data sb.append(resultData + "\n"); SoapObject resultsRequestSOAP = (SoapObject) envelope.bodyIn; System.out.println(resultsRequestSOAP.toString()); } catch (Exception e) { e.printStackTrace(); sb.append("Error:\n" + e.getMessage() + "\n"); } } } `

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  • Ugly thing and advantage of anonymos method -C#

    - by nettguy
    I was asked to explain the ugly thing and advantages of anonymous method. I explained possibly Ugly thing anonymous methods turning quickly into spaghetti code. Advantages We can produce thread safe code using anonymous method :Example static List<string> Names = new List<string>( new string[] { "Jon Skeet", "Marc Gravell", "David", "Bill Gates" }); static List<string> FindNamesStartingWith(string startingText) { return Names.FindAll( delegate(string name) { return name.StartsWith(startingText); }); } But really i did not know whether it is thread safe or not.I was asked to justify it. Can any one help me to understand (1) advantages of anonymous methods (2) Is the above code thread safe or not?

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  • Cannot load JRubyEngine because org.apache.bsf.util.BSFEngineImpl not found

    - by Ceilingfish
    Hi, I'm trying to use JRuby in a custom application, and I don't seem to be able to load the JRubyEngine object. My class looks like functionally similar to this: public class ScriptEngine { private static ScriptEngine engine = new JRubyEngine(); public void run(final String script, final Map<String,Object> input) { final Bindings context = engine.createBindings(); context.putAll(input); try { engine.eval(script,context); } catch (ScriptException e) { log.error("Failed to execute script: "+getScript(),e); } } } However this fails at compilation with the complaint: [javac] Compiling 486 source files to /workspace/myProject/build/src [javac] /workspace/myProject/src/net/ceilingfish/ScriptEngine.java:31: cannot access org.apache.bsf.util.BSFEngineImpl [javac] class file for org.apache.bsf.util.BSFEngineImpl not found [javac] private static ScriptEngine engine = new JRubyEngine(); [javac] ^ [javac] 1 error Does anyone have any insights on where I can get this class from? Or if there is a better way to be instantiating a JRubyEngine object.

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  • A question in java.lang.Integer internal code

    - by Daziplqa
    Hi folks, While looking in the code of the method: Integer.toHexString I found the following code : public static String toHexString(int i) { return toUnsignedString(i, 4); } private static String toUnsignedString(int i, int shift) { char[] buf = new char[32]; int charPos = 32; int radix = 1 << shift; int mask = radix - 1; do { buf[--charPos] = digits[i & mask]; i >>>= shift; } while (i != 0); return new String(buf, charPos, (32 - charPos)); } The question is, in toUnsignedString, why we create a char arr of 32 chars?

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  • Java: custom-exception-error

    - by HH
    $ javac TestExceptions.java TestExceptions.java:11: cannot find symbol symbol : class test location: class TestExceptions throw new TestExceptions.test("If you see me, exceptions work!"); ^ 1 error Code import java.util.*; import java.io.*; public class TestExceptions { static void test(String message) throws java.lang.Error{ System.out.println(message); } public static void main(String[] args){ try { // Why does it not access TestExceptions.test-method in the class? throw new TestExceptions.test("If you see me, exceptions work!"); }catch(java.lang.Error a){ System.out.println("Working Status: " + a.getMessage() ); } } }

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  • Django template not loading properly

    - by fmsf
    Hey, When this one runs everything goes fine: (r"^newobject$", "views.myobjects.newobject"), All the CSS + JS files are properly fetched from: static/css/... static/js/... When this one runs: (r"^mybjects/(([a-z]|[A-Z]|[0-9])+)$","views.myobjects.loadobject"), All the css and JS files that are being fetched, are run trough the urlpatterns and are returning my defailt page: (r"", 'views.main.index'), This makes all my CSS and JS code to actualy be HTML. My guess is that i'm giving some noob mistake. Is there any common reason why this should happen? And how to fix it?

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  • How do I handle all the exceptions in a C# class where both ctor and finalizer throw exceptions?

    - by Frank
    How can I handle all exceptions for a class similar to the following under certain circumstances? class Test : IDisposable { public Test() { throw new Exception("Exception in ctor"); } public void Dispose() { throw new Exception("Exception in Dispose()"); } ~Test() { this.Dispose(); } } I tried this but it doesn't work: static void Main() { Test t = null; try { t = new Test(); } catch (Exception ex) { Console.Error.WriteLine(ex.Message); } // t is still null } I have also tried to use "using" but it does not handle the exception thrown from ~Test(); static void Main() { try { using (Test t = new Test()) { } } catch (Exception ex) { Console.Error.WriteLine(ex.Message); } } Any ideas how can I work around?

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  • [java] Efficiency of while(true) ServerSocket Listen

    - by Submerged
    I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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  • Help Understanding Function

    - by Fred F.
    What does the following function perform? public static double CleanAngle(double angle) { while (angle < 0) angle += 2 * System.Math.PI; while (angle > 2 * System.Math.PI) angle -= 2 * System.Math.PI; return angle; } This is how it is used with ATan2. I believe the actually values passed to ATan2 are always positive. static void Main(string[] args) { int q = 1; //'x- and y-coordinates will always be positive values //'therefore, do i need to "clean"? foreach (Point oPoint in new Point[] { new Point(8,20), new Point(-8,20), new Point(8,-20), new Point(-8,-20)}) { Debug.WriteLine(Math.Atan2(oPoint.Y, oPoint.X), "unclean " + q.ToString()); Debug.WriteLine(CleanAngle(Math.Atan2(oPoint.Y, oPoint.X)), "cleaned " + q.ToString()); q++; } //'output //'unclean 1: 1.19028994968253 //'cleaned 1: 1.19028994968253 //'unclean 2: 1.95130270390726 //'cleaned 2: 1.95130270390726 //'unclean 3: -1.19028994968253 //'cleaned 3: 5.09289535749705 //'unclean 4: -1.95130270390726 //'cleaned 4: 4.33188260327232 }

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  • Hibernate + Spring : cascade deletion ignoring non-nullable constraints

    - by E.Benoît
    Hello, I seem to be having one weird problem with some Hibernate data classes. In a very specific case, deleting an object should fail due to existing, non-nullable relations - however it does not. The strangest part is that a few other classes related to the same definition behave appropriately. I'm using HSQLDB 1.8.0.10, Hibernate 3.5.0 (final) and Spring 3.0.2. The Hibernate properties are set so that batch updates are disabled. The class whose instances are being deleted is: @Entity( name = "users.Credentials" ) @Table( name = "credentials" , schema = "users" ) public class Credentials extends ModelBase { private static final long serialVersionUID = 1L; /* Some basic fields here */ /** Administrator credentials, if any */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public AdminCredentials adminCredentials; /** Active account data */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public Account activeAccount; /* Some more reverse relations here */ } (ModelBase is a class that simply declares a Long field named "id" as being automatically generated) The Account class, which is one for which constraints work, looks like this: @Entity( name = "users.Account" ) @Table( name = "accounts" , schema = "users" ) public class Account extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials the account is linked to */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } And here is the AdminCredentials class, for which the constraints are ignored. @Entity( name = "admin.Credentials" ) @Table( name = "admin_credentials" , schema = "admin" ) public class AdminCredentials extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials linked with an administrative account */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } The code that attempts to delete the Credentials instances is: try { if ( account.validationKey != null ) { this.hTemplate.delete( account.validationKey ); } this.hTemplate.delete( account.languageSetting ); this.hTemplate.delete( account ); } catch ( DataIntegrityViolationException e ) { return false; } Where hTemplate is a HibernateTemplate instance provided by Spring, its flush mode having been set to EAGER. In the conditions shown above, the deletion will fail if there is an Account instance that refers to the Credentials instance being deleted, which is the expected behaviour. However, an AdminCredentials instance will be ignored, the deletion will succeed, leaving an invalid AdminCredentials instance behind (trying to refresh that instance causes an error because the Credentials instance no longer exists). I have tried moving the AdminCredentials table from the admin DB schema to the users DB schema. Strangely enough, a deletion-related error is then triggered, but not in the deletion code - it is triggered at the next query involving the table, seemingly ignoring the flush mode setting. I've been trying to understand this for hours and I must admit I'm just as clueless now as I was then.

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  • How can I limit access to a particular class to one caller at a time in an ASMX web service?

    - by MusiGenesis
    I have a web service method in which I create a particular type of object, use it for a few seconds, and then dispose it. Because of problems arising from multiple threads creating and using instances of this class at the same time, I need to restrict the method so that only one caller at a time ever has one of these objects. To do this, I am creating a private static object: private static object _lock = new object(); ... and then inside the web service method I do this around the critical code: lock (_lock) { using (DangerousObject do = new DangerousObject()) { do.MakeABigMess(); do.CleanItUp(); } } I'm not sure this is working, though. Do I have this right? Will this code ensure that only one instance of DangerousObject is instantiated and in use at a time? Or does each caller get their own copy of _lock, rendering my code here laughable?

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  • Abstract Factory Using Generics: Is Explicitly Converting a Specified Type to Generic a Bad Practice

    - by Merritt
    The question's title says it all. I like how it fits into the rest of my code, but does it smell? public interface IFoo<T> { T Bar { get; set; } } public class StringFoo : IFoo<string> { public string Bar { get; set; } } public static class FooFactory { public static IFoo<T> CreateFoo<T>() { if (typeof(T) == typeof(string)) { return new StringFoo() as IFoo<T>; } throw new NotImplementedException(); } } UPDATE: this is sort of a duplicate of Is the StaticFactory in codecampserver a well known pattern?

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  • Enclosing service execution in try-catch: bad practice?

    - by Sorin Comanescu
    Hi, Below is the usual Program.cs content for a windows service program: static class Program { /// <summary> /// The main entry point for the application. /// </summary> static void Main() { ServiceBase[] ServicesToRun; ServicesToRun = new ServiceBase[] { new MyService() }; ServiceBase.Run(ServicesToRun); } } Is it a bad practice to enclose the ServiceBase.Run(...) in a try-catch block? Thanks.

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  • Saving a reference to a int.

    - by Scott Chamberlain
    Here is a much simplified version of what I am trying to do static void Main(string[] args) { int test = 0; int test2 = 0; Test A = new Test(ref test); Test B = new Test(ref test); Test C = new Test(ref test2); A.write(); //Writes 1 should write 1 B.write(); //Writes 1 should write 2 C.write(); //Writes 1 should write 1 Console.ReadLine(); } class Test { int _a; public Test(ref int a) { _a = a; //I loose the reference here } public void write() { var b = System.Threading.Interlocked.Increment(ref _a); Console.WriteLine(b); } } In my real code I have a int that will be incremented by many threads however where the threads a called it will not be easy to pass it the parameter that points it at the int(In the real code this is happening inside a IEnumerator). So a requirement is the reference must be made in the constructor. Also not all threads will be pointing at the same single base int so I can not use a global static int either. I know I can just box the int inside a class and pass the class around but I wanted to know if that is the correct way of doing something like this? What I think could be the correct way: static void Main(string[] args) { Holder holder = new Holder(0); Holder holder2 = new Holder(0); Test A = new Test(holder); Test B = new Test(holder); Test C = new Test(holder2); A.write(); //Writes 1 should write 1 B.write(); //Writes 2 should write 2 C.write(); //Writes 1 should write 1 Console.ReadLine(); } class Holder { public Holder(int i) { num = i; } public int num; } class Test { Holder _holder; public Test(Holder holder) { _holder = holder; } public void write() { var b = System.Threading.Interlocked.Increment(ref _holder.num); Console.WriteLine(b); } } Is there a better way than this?

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  • How do I get around Inconsistant accessibilty error in C # ?

    - by xarzu
    How do I get around Inconsistant accessibilty error in C # ? I need to pass a pointer to a node in a linked list to a method. When I do, I get a "Compiler Error CS0051" Example The following sample generates CS0051: Copy Code // CS0051.cs public class A { // Try making B public since F is public // B is implicitly private here class B { } public static void F(B b) // CS0051 { } public static void Main() { } } That is a simple example. The actual program is a bit more complicated. I am actually using a node in a linked list to pass to the method LinkedListNode node The method uses recursion because the node is mart of a huge linked list structure of linked lists that outputs an xml file. Either I have to find a way to use recursion without using methods or I need to find a way to pass pointers nodes or actual nodes.

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  • jquery plugin with multiple functions

    - by tcurdt
    According to the developer documentation jquery plugins are supposed to have only one namespace for all functions they make available. Which is straight forward as long as you only expose a single function per context (static/element). (function($){ var state_a = 0, $.myplugin = function(in_options) { // static return this; } $.fn.myplugin = function(in_options) { // element return this; } })(jQuery); This makes calls like this possible: $("elem").myplugin(options); jQuery.myplugin(options); What's the best approach if you have more than one function and need to share state? I would like to call into my plugin like this: $("elem").myplugin.start(options); $("elem").myplugin.stop(); jQuery.myplugin.start(options); jQuery.myplugin.stop();

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  • The .NET ActiveX component with WPF content can't be loaded by non MFC app

    - by lonelyflyer
    I have a legacy delphi program and want to add some content implemented with WPF. So I encapsulate the WPF control with a .NET/ActiveX interop technology. That means something like: [ComRegisterFunction()] public static void RegisterClass(string key); [ComUnregisterFunction()] public static void UnregisterClass(string key); The activeX component is a WinForms User Control and the WPF materials are attached to an ElemenHost in this User Control. It works fine if the host app of this ActiveX is a MFC program even without /clr switch. But my legacy app is a delphi program, and it always throw a stackoverflow exception within the constructor of my WPF user control as the program be started. I have no clue, Google is no help. and it has puzzled me for days.

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  • ORACLE using function parametes in where claus

    - by Gainder
    Hello, I have created a simple static function in oracle 10g to get the reference of an object based on his pk. STATIC FUNCTION getRef(nome IN VARCHAR2) RETURN REF folder_typ IS fl_r REF folder_typ := null; BEGIN SELECT REF(fl) INTO fl_r FROM folder_tab fl WHERE fl.nome = nome; RETURN fl_r; END getRef; This gives me an error because he could't fetch the row. If insted of WHERE fl.nome = nome; I write WHERE fl.nome = 'folder1'; insted of passing it as parameter it works. I think im not using the parameter in the right way. How can I use it?

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  • Date exception when trying to use date method

    - by Simon Andi
    Hi, I have defined a object model where one of the array elements is a string public static String[] columnNames6 = {"Total Shares", "Total Calls", "Call Strike", "Call Premium", "Call Expiry" }; public static Object[][] data6 = { { new Double(0), new Double(0), new Double(0), new Double(0),"dd/mm/yyyy"}, }; I then use the following code to get the date so that I can use the data method but having no joy - Can someone please tell me why it is throwing an exception after I do this String ExpiryDate = (String)GV.data6[0][4]; System.out.println("DATE STRING IS: " + ExpiryDate); Date EndOptionDate = new Date(ExpiryDate); // SOMETHING WRONG HERE even though it compiles okay //Get Todays's Date Date TodaysDate = new Date(); //Calculate Days Option Expiry long DaysDifference = EndOptionDate.getTime() - TodaysDate.getTime(); Would really appreciate some help as really stuck not sure how I should code the line in bold - new to java, so please excuses my lack of knowledge looked at tutorials can't seem to move forward. Thanks Simon

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  • Structuring Win32 GUI code

    - by kraf
    I wish to improve my code and file structure in larger Win32 projects with plenty of windows and controls. Currently, I tend to have one header and one source file for the entire implementation of a window or dialog. This works fine for small projects, but now it has come to the point where these implementations are starting to reach 1000-2000 lines, which is tedious to browse. A typical source file of mine looks like this: static LRESULT CALLBACK on_create(const HWND hwnd, WPARAM wp, LPARAM lp) { setup_menu(hwnd); setup_list(hwnd); setup_context_menu(hwnd); /* clip */ return 0; } static LRESULT CALLBACK on_notify(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { const NMHDR* header = (const NMHDR*)lp; /* At this point I feel that the control's event handlers doesn't * necessarily belong in the same source file. Perhaps I could move * each control's creation code and event handlers into a separate * source file? Good practice or cause of confusion? */ switch (header->idFrom) { case IDC_WINDOW_LIST: switch (header->code) { case NM_RCLICK: return on_window_list_right_click(hwnd, wp, lp); /* clip */ } } } static LRESULT CALLBACK wndmain_proc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { switch (msg) { case WM_CREATE: return on_create(hwnd, wp, lp); case WM_CLOSE: return on_close(hwnd, wp, lp); case WM_NOTIFY: return on_notify(hwnd, wp, lp); /* It doesn't matter much how the window proc looks as it just forwards * events to the appropriate handler. */ /* clip */ default: return DefWindowProc(hwnd, msg, wp, lp); } } But now as the window has a lot more controls, and these controls in turn have their own message handlers, and then there's the menu click handlers, and so on... I'm getting lost, and I really need advice on how to structure this mess up in a good and sensible way. I have tried to find good open source examples of structuring Win32 code, but I just get more confused since there are hundreds of files, and within each of these files that seem GUI related, the Win32 GUI code seems so far encapsulated away. And when I finally find a CreateWindowEx statement, the window proc is nowhere to be found. Any advice on how to structure all the code while remaining sane would be greatly appreciated. Thanks! I don't wish to use any libraries or frameworks as I find the Win32 API interesting and valuable for learning. Any insight into how you structure your own GUI code could perhaps serve as inspiration.

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  • Reducing Code Repetition: Calling functions with slightly different signatures

    - by Brian
    Suppose I have two functions which look like this: public static void myFunction1(int a, int b, int c, string d) { //dostuff someoneelsesfunction(c,d); //dostuff2 } public static void myFunction2(int a, int b, int c, Stream d) { //dostuff someoneelsesfunction(c,d); //dostuff2 } What would be a good way to avoid repeated dostuff? Ideas I've thought of, but don't like: I could make d an object and cast at runtype based on type, but this strikes me as not being ideal; it removes a type check which was previously happening at compile time. I could also write a private helper class that takes an object and write both signatures as public functions. I could replace dostuff and dostuff2 with delegates or function calls or something.

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  • Codeigniter MVC controller architecture

    - by justinbach
    I'm building a site using CodeIgniter that largely consists of static content (although there will be a relatively small CMS backend, and there's code to handle localization/internationalization based on the domain used to access it). Typically, in a situation like this, I'd use a Pages controller that is in charge of rendering static content, but as there are a fair number of pages on the site (30+) it'd quickly end up containing lots of methods (assuming one per page). Should I break my Pages controller into multiple controllers (that perhaps inherit from it) according to different sections of the site? Should I organize methods differently in the Pages controller? What's the best practice here? Thanks! Justin

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  • Java assert nasty side-effect - compiler bug?

    - by Alex
    This public class test { public static void main(String[] args) { Object o = null; assert o != null; if(o != null) System.out.println("o != null"); } } prints out "o != null"; both 1.5_22 and 1.6_18. Compiler bug? Commenting out the assert fixes it. The byte code appears to jump directly to the print statement when assertions are disabled: public static main(String[]) : void L0 LINENUMBER 5 L0 ACONST_NULL ASTORE 1 L1 LINENUMBER 6 L1 GETSTATIC test.$assertionsDisabled : boolean IFNE L2 ALOAD 1: o IFNONNULL L2 NEW AssertionError DUP INVOKESPECIAL AssertionError.<init>() : void ATHROW L2 LINENUMBER 8 L2 GETSTATIC System.out : PrintStream LDC "o != null" INVOKEVIRTUAL PrintStream.println(String) : void L3 LINENUMBER 9 L3 RETURN L4

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