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  • Why does Java allow to implement different interfaces, each containing a method with the same signature?

    - by Software Engeneering Learner
    I've recently found that I can have two interfaces containing method with the same signature as a method in the other interface. And then I can have an interface or class that implements both of that interfaces. So the descendant class/interface has implicitly implements two different methods as a one method. Why is this allowed in Java? I can see a numerous problems that arises from that. Even eclipse only can find out about implementations for only one interface method, but for the second one it doesn't show any implementations at all. Also I believe there would be problems with automatic refactoring, like when you would like to change the signature of the method in one of the interfaces and IDE won't be able to correctly change that signature in all implementations, as they implement two different interfaces and how will IDE know what interface method it implementation descends. Why don't just make a compiler error like 'interfaces method names clashes' or something like that?

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  • Calling a method in a view controller from a view

    - by Lakshmie
    I have to invoke a method present in a view controller who's reference is available in the view. When I try to call the method like any other method, for some reason, iPhone just ignores the call. Can somebody explain as to why this happens and also how can I go about invoking this method? In the view I have this method: -(void) touchesBegan :(NSSet *) touches withEvent:(UIEvent *)event{ NSArray* mySubViews = [self subviews]; for (UITouch *touch in touches) { int i = 0; for(; i<[mySubViews count]; i++){ if(CGRectContainsPoint([[mySubViews objectAtIndex:i] frame], [touch locationInView:self])){ break; } } if(i<[mySubViews count]){ // viewController is the reference to the View Controller. [viewController pointToSummary:[touch locationInView:self].y]; NSLog(@"Helloooooo"); break; } } } Whenever the touches event is triggered, Hellooooo gets printed in the console but the method before that is simply ignored

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  • MySQL ORDER BY DESC is fast but ASC is very slow

    - by Pepper
    Hello, I'm completely stumped on this one. For some reason when I sort this query by DESC it's super fast, but if sorted by ASC it's extremely slow. This takes about 150 milliseconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published DESC LIMIT 0, 50; This takes about 32 seconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published ASC LIMIT 0, 50; The EXPLAIN is the same for both queries. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts index NULL published 5 NULL 50 Using where I've tracked it down to "USE INDEX (published)". If I take that out it's the same performance both ways. But the EXPLAIN shows the query is less efficient overall. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts range feed_id feed_id 4 \N 759 Using where; Using filesort And here's the table. CREATE TABLE `posts` ( `id` int(20) NOT NULL AUTO_INCREMENT, `feed_id` int(11) NOT NULL, `post_url` varchar(255) NOT NULL, `title` varchar(255) NOT NULL, `content` blob, `author` varchar(255) DEFAULT NULL, `published` int(12) DEFAULT NULL, `updated` datetime NOT NULL, `created` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `post_url` (`post_url`,`feed_id`), KEY `feed_id` (`feed_id`), KEY `published` (`published`) ) ENGINE=InnoDB AUTO_INCREMENT=196530 DEFAULT CHARSET=latin1; Is there a fix for this? Thanks!

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  • Which one is better offline method for large scale application

    - by Manish Pansiniya
    We've a big data management website used by several property. Some of our customers have downtime (they can't access net for an hour or two). We want our site to support offline data viewing and inventory management (typical data search and add/remove) and when the user goes online we can sync the changes back to our central database. Customers use several platforms like Windows, iOS, etc. We've been looking into several different options, here are the major choices - Develop offline web app supported in HTML5. Develop a 'fallback' mechanism and interact with data from the app cache as explained in here (http://www.htmlgoodies.com/html5/tutorials/introduction-to-offline-web- applications-using-) Develop a desktop based cross platform solution. I remember the old MONO which has been popular. Here's a post (What do you suggest for cross platform apps, including web cross-platform-apps-including-web) and another one (Technology choice for cross platform development (desktop and phone)? platform-development-desktop-and-phone?rq=1) I realize the the desktop solution might be hard to maintain and result in some compatibility issues and demand test environments. Can HTML5 handle moderate to high level complexity and data flow? Or would it be better to rely on a desktop based app for better scalability & performance?

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  • Alternate method to dependent, nested if statements to check multiple states

    - by octopusgrabbus
    Is there an easier way to process multiple true/false states than using nested if statements? I think there is, and it would be to create a sequence of states, and then use a function like when to determine if all states were true, and drop out if not. I am asking the question to make sure there is not a preferred Clojure way to do this. Here is the background of my problem: I have an application that depends on quite a few input files. The application depends on .csv data reports; column headers for each report (.csv files also), so each sequence in the sequence of sequences can be zipped together with its columns for the purposes of creating a smaller sequence; and column files for output data. I use the following functions to find out if a file is present: (defn kind [filename] (let [f (File. filename)] (cond (.isFile f) "file" (.isDirectory f) "directory" (.exists f) "other" :else "(cannot be found)" ))) (defn look-for [filename expected-type] (let [find-status (kind-stat filename expected-type)] find-status)) And here are the first few lines of a multiple if which looks ugly and is hard to maintain: (defn extract-re-values "Plain old-fashioned sub-routine to process real-estate values / 3rd Q re bills extract." [opts] (if (= (utl/look-for (:ifm1 opts) "f") 0) ; got re columns? (if (= (utl/look-for (:ifn1 opts) "f") 0) ; got re data? (if (= (utl/look-for (:ifm3 opts) "f") 0) ; got re values output columns? (if (= (utl/look-for (:ifm4 opts) "f") 0) ; got re_mixed_use_ratio columns? (let [re-in-col-nams (first (utl/fetch-csv-data (:ifm1 opts))) re-in-data (utl/fetch-csv-data (:ifn1 opts)) re-val-cols-out (first (utl/fetch-csv-data (:ifm3 opts))) mu-val-cols-out (first (utl/fetch-csv-data (:ifm4 opts))) chk-results (utl/chk-seq-len re-in-col-nams (first re-in-data) re-rec-count)] I am not looking for a discussion of the best way, but what is in Clojure that facilitates solving a problem like this.

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  • bash: listing files in date order, with spaces in filenames

    - by Jason Judge
    I am starting with a file containing a list of hundreds of files (full paths) in a random order. I would like to list the details of the ten latest files in that list. This is my naive attempt: ls -las -t `cat list-of-files.txt` | head -10 That works, so long as none of the files have spaces in, but fails if they do as those files are split up at the spaces and treated as separate files. I have tried quoting the files in the original list-of-files file, but the here-document still splits the files up at the spaces in the filenames. The only way I can think of doing this, is to ls each file individually (using xargs perhaps) and create an intermediate file with the file listings and the date in a sortable order as the first field in each line, then sort that intermediate file. However, that feels a bit cumbersome and inefficient (hundreds of ls commands rather than one or two). But that may be the only way to do it? Is there any way to pass "ls" a list of files to process, where those files could contain spaces - it seems like it should be simple, but I'm stumped.

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  • Calling a method with an instance of derived class of derived generic type

    - by madsbirk
    Okay, so I have classes class B<T> : A<T> class L : K and a method void Method(A<K> a) {...} What I would like to do is this b = new B<L>(); Method(b); //error But it is not possible to b to the correct type. Indeed it is not possible to make this cast A<K> t = new A<L>(); //error I would really like to not have to change the internals of Method. I have no problems making changes to B and/or L. Do I have any options for making some sort of workaround? I guess it should be possible for Method to execute all of its method calls etc. on b, since B derives from A and L derives from K?

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  • Controlling the order of PicoContainer startup

    - by Trejkaz
    I have been tasked with doing some refactoring work on how we start up applications. Basically we have a bunch of console apps which were depending on the GUI application startup code, causing bogus dependencies which have kick-on effects for which libraries we need to ship, and which dependencies other modules need to declare. So I have written a simple startup framework where I basically just throw a bunch of Runnable objects into a list and then run them in order - and it works. But I was thinking - we already have PicoContainer in our project, so all these things that need to be run on startup could potentially be thrown into a PicoContainer, and if they implement Startable they will start... But in some cases we want to specify the ordering between them. For example, I don't want any other component writing to the log before we write a header into the log indicating that the application is starting up. I know I can introduce ordering by introducing injection dependencies, but this feels like a hack in this case - I would need to add the log header writer as a dependency for every other component which might write to the log, which isn't great at all. Nonetheless it seems like it would be nice to control the order of PicoContainer startup, so is there perhaps some other way? Alternatively I could just keep it simple and stick to my list of Runnable. It does, after all, work.

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  • How my Website looks like under Different Screen Resolutions?

    - by strakastroukas
    Back in the past, i found a third party webpage that was able to capture and save images of my website in different resolutions and browsers. Of course i have no more that bookmark... So is there any webpage or application where i can see how my webpage looks like in different resolution? And here are the resolutions i would like to check for... 1. 1024x768 24.56% 2. 1280x800 22.06% 3. 1280x1024 13.42% 4. 1366x768 7.10% 5. 1440x900 6.68%

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  • Correct way to generate order numbers in SQL Server

    - by Anton Gogolev
    This question certainly applies to a much broader scope, but here it is. I have a basic ecommerce app, where users can, naturally enough, place orders. Said orders need to have a unique number, which I'm trying to generate right now. Each order is Vendor-specific. Basically, I have an OrderNumberInfo (VendorID, OrderNumber) table. Now whenever a customer places an order I need to increment OrderNumber for a particuar Vendor and return that value. Naturally, I don't want other processes to interfere with me, so I need to exclusively lock this row somehow: begin tranaction declare @n int select @n = OrderNumber from OrderNumberInfo where VendorID = @vendorID update OrderNumberInfo set OrderNumber = @n + 1 where OrderNumber = @n and VendorID = @vendorID commit transaction Now, I've read about select ... with (updlock rowlock), pessimistic locking, etc., but just cannot fit all this in a coherent picture: How do these hints play with SQL Server 2008s' snapshot isolation? Do they perform row-level, page-level or even table-level locks? How does this tolerate multiple users trying to generate numbers for a single Vendor? What isolation levels are appropriate here? And generally - what is the way to do such things?

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  • Spring bean's DESTROY-METHOD attribute [does not work for me]

    - by EugeneP
    Can get work the attribute "destroy-method". First, even if I type non-existing method name into "destroy-method" attribute, Spring initialization completes fine (already strange!). Next, when a bean has a "prototype" scope, then I suppose it must be destroyed before the application is closed. That not happens, it is simply never called in my case. Though, after extracting this bean I can call this method explicitly and it does its job. Could you explain why this method is never called in my Spring 2.5 case? p.s. The method exists, it is public and has no arguments.

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  • Can't find method in the activity

    - by Synesso
    I'm starting with Scala + Android. I'm trying to wire a button action to a button without the activity implementing View.OnClickListener. The button click fails at runtime because the method cannot be found. The document I'm working through says that I need only declare a public void method taking a View on the action, and use that method name in the layout. What have I done wrong? MainActivity.scala package net.badgerhunt.hwa import android.app.Activity import android.os.Bundle import android.widget.Button import android.view.View import java.util.Date class MainActivity extends Activity { override def onCreate(savedInstanceState: Bundle) = { super.onCreate(savedInstanceState) setContentView(R.layout.main) } def calculate(button: View): Unit = println("calculating with %s ...".format(button)) } res/layout/main.xml <?xml version="1.0" encoding="utf-8"?> <Button xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/button" android:text="" android:onClick="calculate" android:layout_width="fill_parent" android:layout_height="fill_parent"/> the failure onclick D/AndroidRuntime( 362): Shutting down VM W/dalvikvm( 362): threadid=3: thread exiting with uncaught exception (group=0x4001b188) E/AndroidRuntime( 362): Uncaught handler: thread main exiting due to uncaught exception E/AndroidRuntime( 362): java.lang.IllegalStateException: Could not find a method calculate(View) in the activity E/AndroidRuntime( 362): at android.view.View$1.onClick(View.java:2020) E/AndroidRuntime( 362): at android.view.View.performClick(View.java:2364) E/AndroidRuntime( 362): at android.view.View.onTouchEvent(View.java:4179) E/AndroidRuntime( 362): at android.widget.TextView.onTouchEvent(TextView.java:6540) E/AndroidRuntime( 362): at android.view.View.dispatchTouchEvent(View.java:3709) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107) E/AndroidRuntime( 362): at android.app.Activity.dispatchTouchEvent(Activity.java:2061) E/AndroidRuntime( 362): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643) E/AndroidRuntime( 362): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691) E/AndroidRuntime( 362): at android.os.Handler.dispatchMessage(Handler.java:99) E/AndroidRuntime( 362): at android.os.Looper.loop(Looper.java:123) E/AndroidRuntime( 362): at android.app.ActivityThread.main(ActivityThread.java:4363) E/AndroidRuntime( 362): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime( 362): at java.lang.reflect.Method.invoke(Method.java:521) E/AndroidRuntime( 362): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) E/AndroidRuntime( 362): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) E/AndroidRuntime( 362): at dalvik.system.NativeStart.main(Native Method) E/AndroidRuntime( 362): Caused by: java.lang.NoSuchMethodException: calculate E/AndroidRuntime( 362): at java.lang.ClassCache.findMethodByName(ClassCache.java:308) E/AndroidRuntime( 362): at java.lang.Class.getMethod(Class.java:1014) E/AndroidRuntime( 362): at android.view.View$1.onClick(View.java:2017) E/AndroidRuntime( 362): ... 20 more

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  • Compare Two NameValueCollections Extension Method

    - by Jon Canning
    public static class NameValueCollectionExtension     {         public static bool CollectionEquals(this NameValueCollection nameValueCollection1, NameValueCollection nameValueCollection2)         {             return nameValueCollection1.ToKeyValue().SequenceEqual(nameValueCollection2.ToKeyValue());         }         private static IEnumerable<object> ToKeyValue(this NameValueCollection nameValueCollection)         {             return nameValueCollection.AllKeys.OrderBy(x => x).Select(x => new {Key = x, Value = nameValueCollection[x]});         }     }

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  • What tool can I use to test my web app in different resolutions?

    - by strakastroukas
    Back in the past, i found a third party webpage that was able to capture and save images of my website in different resolutions and browsers. Of course i have no more that bookmark... So is there any webpage or application where i can see how my webpage looks like in different resolution? And here are the resolutions i would like to check for... 1. 1024x768 24.56% 2. 1280x800 22.06% 3. 1280x1024 13.42% 4. 1366x768 7.10% 5. 1440x900 6.68%

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  • Useful Extension Method for ICloneable

    - by DesigningCode
    In the past, I’ve had to put a type specific clone in each cloneable class, but with extension methods you can write a generic T specific clone class Program { static void Main(string[] args) { var b = new Blah() {X = 1, Y = 2}; var bb = b.Clone(); Console.WriteLine(string.Format("{0} {1}", bb.X, bb.Y)); } } public class Blah : ICloneable { public int X; public int Y; object ICloneable.Clone() { return MemberwiseClone(); } } public static class CloneExtension { public static T Clone<T>(this T o) where T : ICloneable { return (T)o.Clone(); } }

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  • can you have too many dto/bo - mapping method

    - by Fredou
    I have a windows service, 2 web services and a web interface that need to follow the same path (data wise). So I came up with two ways of creating my solution. My concern is the fact that the UI/WS/etc will have their own kind of DTO (let's say the model in ASP.Net MVC) that should be mapped to a DTO so the SL can then map it to a BO then mapping it to the proper EF6 DTO so that I can save it in a database. So I'm thinking of doing it this way to remove one level of mapping. Which one should I take? Or is there a 3rd solution?

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  • Smoothing Small Data Set With Second Order Quadratic Curve

    - by Rev316
    I'm doing some specific signal analysis, and I am in need of a method that would smooth out a given bell-shaped distribution curve. A running average approach isn't producing the results I desire. I want to keep the min/max, and general shape of my fitted curve intact, but resolve the inconsistencies in sampling. In short: if given a set of data that models a simple quadratic curve, what statistical smoothing method would you recommend? If possible, please reference an implementation, library, or framework. Thanks SO!

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  • Best Method of function parameter validation

    - by Aglystas
    I've been dabbling with the idea of creating my own CMS for the experience and because it would be fun to run my website off my own code base. One of the decisions I keep coming back to is how best to validate incoming parameters for functions. This is mostly in reference to simple data types since object validation would be quite a bit more complex. At first I debated creating a naming convention that would contain information about what the parameters should be, (int, string, bool, etc) then I also figured I could create options to validate against. But then in every function I still need to run some sort of parameter validation that parses the parameter name to determine what the value can be then validate against it, granted this would be handled by passing the list of parameters to function but that still needs to happen and one of my goals is to remove the parameter validation from the function itself so that you can only have the actual function code that accomplishes the intended task without the additional code for validation. Is there any good way of handling this, or is it so low level that typically parameter validation is just done at the start of the function call anyway, so I should stick with doing that.

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  • Guaranteed Restore Points as Fallback Method

    - by Mike Dietrich
    Thanks to the great audience yesterday in the Upgrade & Migration Workshop in Utrecht. That was really fun and I was amazed by our new facilities (and the  "wellness" lights surrounding the plenum room's walls). And another reason why I like to do these workshops is that often I learn new things from you So credits here to Rick van  Ek who has highlighted the following topic to me. Yesterday (and in some previous workshops) I did mention during the discussion about Fallback Strategies that you'll have to switch on Flashback Database beforehand to create a guaranteed restore point in case you'll encounter an issue during the database upgrade. I knew that we've made it possible since Oracle Database 11.2 to switch Flashback Database on without taking the database into MOUNT status (you could switch it off anyway while the database is open before in all releases). But before Oracle Database 11.2 that did require MOUNT status. SQL> create restore point rp1 guarantee flashback database ; create restore point rp1 guarantee flashback database * ERROR at line 1: ORA-38784: Cannot create restore point 'RP1'. ORA-38787: Creating the first guaranteed restore point requires mount mode when flashback database is off. But Rick did mention that I won't need to switch Flashback Database On to create a guaranteed restore point. And he's right - in older releases I would have had to go into MOUNT state to define the restore point which meant to restart the database. But in 11.2 that's no necessary anymore. And the same will apply when you upgrade your pre-11.2 database (e.g. an Oracle Database 10.2.0.4) to Oracle Database 11.2. As soon as you start your "old" not-yet-upgraded database in your 11.2 environment with STARTUP UPGRADE you can define a guaranteed restore point. If you tail the alert.log you'll see that the database will start the RVWR (Recovery Writer) background process - you'll just have to make sure that you'd define the values for db_recovery_file_dest_size and db_recovery_file_dest. SQL> startup upgrade ORACLE instance started. Total System Global Area  417546240 bytes Fixed Size                  2228944 bytes Variable Size             134221104 bytes Database Buffers          272629760 bytes Redo Buffers                8466432 bytes Database mounted. Database opened. SQL> create restore point grpt guarantee flashback database; Restore point created.SQL> drop restore point grpt; And don't forget to drop that restore point the sooner or later as it is guaranteed - and will fill up your Fast Recovery Area pretty quickly Just on the side: in any case archivelog mode is required if you'd like to work with restore points. - Mike

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  • Application development : method to manage backgound process

    - by Simon Dubois
    I am developing an application with different behavior depending on the arguments : - "-config" starts a Gtk window to change options, start and close the daemon. - "-daemon" starts a background process that does something every X minutes. I already know how to use fork/system/exec etc... But I would like to know the main logic of such application to : - restart or refresh the daemon when configuration change. - keep only one instance of the daemon. I have red that killing the daemon to restart it is not a clean way to do. How other applications do ? (ubuntuone, weather forecast, rss feed working with notification area) Thanks for your help. PS : I don't want to create a system-wide daemon, just a user application with a background process.

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  • OOP private method parameters coding style

    - by Jake
    After coding for many years as a solo programmer, I have come to feel that most of the time there are many benefits to write private member functions with all of the used member variables included in the parameter list, especially development stage. This allow me to check at one look what member variables are used and also allow me to supply other values for tests and debugging. Also, a change in code by removing a particular member variable can break many functions. In this case however, the private function remains isolated am I can still call it using other values without fixing the function. Is this a bad idea afterall, especially in a team environment? Is it like redundant or confusing, or are there better ways?

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