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  • How to know file type without extension

    - by Ayusman
    While trying to come-up with a servlet based application to read files and manipulate them (image type conversion) here is a question that came up to me: Is it possible to inspect a file content and know the filetype? Is there a standard that specifies that each file MUST provide some type of marker in their content so that the application will not have to rely on the file extension constraints? Consider an application scenario: I am creating an application that will be able to convert different file formats to a set of output formats. Say user uploads an PDF, my application can suggest that the possible conversion formats are microsoft word or TIFF or JPEG etc. As my application will gradually support different file formats (over a period of time), I want my application to inspect the input file instead of having the user to specify the format. And suggest to user the possible formats of output. I understand this is an open ended, broad question. Please let me know if it needs to be modified. Thanks, Ayusman

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  • How can I know whether my C++ string variable is a number or not

    - by user342580
    I have a string of class string string str; how can I check if it is a number or not, str can only have 3 possible types described below like abcd or a number like 123.4 or a number with a parenthesis attach to the end it for example 456) note the parenthesis at the end of "str" is the only possible combination of number and none number where the bottom two are considered valid numbers, I know I could use lexical_cast if only the first 2 cases occur, but how about considering all 3 possible cases to occur? I don't need to do anything fancy with str, I just need to know whether it is a valid number as I described

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  • How to know who kills my threads

    - by mcabral
    I got a thread that is just banishing.. i'd like to know who is killing my thread and why. It occurs to me my thread is being killed by the OS, but i'd like to confirm this and if possible to know why it's killing it. As for the thread, i can assert it has at least 40 min of execution before dying, but it suddenly dies around 5 min. public void RunWorker() { Thread worker = new Thread(delegate() { DoSomethingForALongLongTime(); }); worker.IsBackground = true; worker.SetApartmentState(System.Threading.ApartmentState.STA); worker.Start(); }

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  • Java: Reflection against casting when you know superclass

    - by Ema
    I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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  • Ruby: how to know depth of multidemensional array

    - by hqt
    This is my problem I have met in my assignment. Array A has two elements: array B and array C. Array B has two elements: array D and array E At some point, array X just contains two elements: string a and string b. I don't know how to determine how deep array A is. For example: arrA = [ [ [1,2] ] ] I have tested by: A[0][0][0] == nil which returns false. Moreover, A[0][0]..[0] == nil always returns false. So, I cannot do this way to know how deep array A is.

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  • How do IOS know which viewController is being viewed and hence need viewWillAppear to be called

    - by Jim Thio
    How does iOs know? Does each view has a pointer to it's controller? What happened? When we pop a viewController from navigation, does the navigationController arrange which view should be called? For example: If I added: [[BNUtilitiesQuick window] addSubview:[BNUtilitiesQuick searchController].view]; viewWillAppear will be called. However, window doesn't know the viewController. I am passing the view outlet of the controller not the controller. How can iOs 5 knows that it has to call [[BNUtilitiesQuick searchController] viewWillAppear:YES]

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  • Usage of setInfoClass() on DirectoryIterator vs on RecursiveDirectoryIterator

    - by Gordon
    I've ran into an inconsistent behavior when using setInfoClass to set a custom SplFileInfo class to a DirectoryIterator versus setting it to a RecursiveIterator. The method description states: Use this method to set a custom class which will be used when getFileInfo and getPathInfo are called. The class name passed to this method must be derived from SplFileInfo. Consider this custom SplFileInfo class A extends SplFileInfo { public function test() { printf("I am of class %s\n", __CLASS__); } } and my iterators $iterator = new DirectoryIterator('.'); and $iterator = new RecursiveDirectoryIterator('.'); Now I'd expect those two to behave the same when I do $iterator->setInfoClass('A'); foreach($iterator as $file) { $file->test(); } and output 'I am of A' for each $file encountered and in fact, the RecursiveDirectoryIterator will do that. But the DirectoryIterator will raise Fatal error: Call to undefined method DirectoryIterator::test() so apparently the InfoClass does not get applied when iterating over the files. At least not directly, because when I change the code in the foreach loop to $file->getPathInfo()->test(); it will work for the DirectoryIterator. But then the RecursiveDirectoryIterator will raise Fatal error: Call to undefined method SplFileInfo::test() Like I said, I'd expect those two to behave the same, but apparently getFileInfo and getPathInfo don't get called in the DirectoryIterator, which I consider a bug. So if there is any Iterator experts out there, please help me understand this. Thanks.

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  • Does anyone know how to detect whether a Windows Service is running through Java

    - by GKelly
    There's plenty of information on running Java apps as services, but I need to know how to detect whether a windows service is running or not. Does anyone know how??? At the DOS prompt, I can run: tasklist /svc|findstr "NonRunningService" echo Return code for N onRunningService is %ERRORLEVEL% tasklist /svc|findstr "RunningService" echo Return code for RunningService is %ERRORLEVEL% I get the following: Return code for NonRunningService is 1 Return code for RunningService is 0 In code, I have: int retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"NonRunningService\"").waitFor(); System.out.println("Return code for NonRunningService is " + retCode); retCode = Runtime.getRuntime.exec("tasklist /svc|findstr \"RunningService\"").waitFor(); System.out.println("Return code for RunningService is " + retCode); I get the following output Return code for NonRunningService is 1 Return code for RunningService is 1 According to the JavaDocs, the waitFor() should block until the process finishes, and give me the exit value of the process. I've also tried using the Process/ProcessBuilder command line calls: //'tasklist /nh /fi "SERVICES eq RunningService"' will return a line for // each running service of the requested type. Process p1 = new ProcessBuilder("tasklist", "/nh", "/fi" "SERVICES eq RunningService").start(); p1.waitFor(); BufferedReader is = new BufferedReader(new InputStreamReader(p1.getInputStream())); String line = is.readLine(); System.out.println("Service - " + line); System.out.println("Running? ", (line==null?"No":"Yes"); gives: Service - Running? No even when I get lines in the output at the command line!

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  • What should every developer know about databases?

    - by Aaronaught
    Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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  • I don't know How to release NSString.

    - by Beomseok
    NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [path objectAtIndex:0]; NSString *databasePath = [documentsDirectory stringByAppendingPathComponent:@"DB"]; NSString *fileName = [newWordbookName stringByAppendingString:@".csv"]; NSString *fullPath = [databasePath stringByAppendingPathComponent:fileName]; [[NSFileManager defaultManager] createFileAtPath:fullPath contents:nil attributes:nil]; [databasePath release]; //[fileName release]; Error! //[fullPath release]; Error! //NSLog(@"#1 :databasePath: %d",[databasePath retainCount]); //NSLog(@"#1 :fileName: %d",[fileName retainCount]); //NSLog(@"#1 :fullPath: %d",[fullPath retainCount]); Hi guys, I'm using this code and want to release NSString* .. so, I declare fileName, fullPath, and databasePath of NSString. But database is released, fileName, fullpath doen't release. I don't know why it happen. I know that NSArray is Autoreleased. But Is documentsDirectory autoreleased? (newWordbookName is nsstring type) I hope that I look through a document about iPhone memory management. Please advice for me.

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  • How to react when asked a question you already know during an interview

    - by DevNull
    The short story:- If you are asked a tough algorithmic/puzzle question during an interview, whose solution is already known to you, do you:- Honestly tell the interviewer that you know this question already? -- this could result in bursting the interviewer's ego and him increasing the complexity level of the subsequent questions. Do an Oscar deserving performance and act as if you are thinking and trying hard and slowly getting to the solution? -- depending on your acting skills, could majorly impress the interviewer making the rest of the interview easier. Long story:- OK, this question comes as a result of what happened to me in a recent telephonic interview that I gave - the interview was supposed to be all algorithmic. The interviewer started with an algorithmic question which I had luckily already seen here on Stackoverflow. The best solution to that problem is not very intuitive and is more of a you-get-it-if-you-know-it kind. Now, just to not disappoint the interviewer too much, I took a few seconds as if I was pondering on the problem and then blurted out the answer which I knew too well having read and admired it on SO already. But I guess that gave it away to the interviewer that I already knew this question and since then, he started asking me for more efficient solutions and I kept coming up with approaches (even if not correct or more efficient, but I did touch a lot of different data structures and algos) and he kept asking for more efficient solutions and generally seemed put off by my initial salvo which was unexpected. What should I have done? Cheers!

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  • I'm about to learn x86 assembly on os x 10.6 let me know how compile..plz

    - by kevin choung
    hello~ I'm about to learn x86 assembly language on mac os x... I'm using as instruction to compile assembly file in commend window. but I have several errors.. and I don't know how I can get through.. here is the errors and my assembly code.. which is quite simple. **ung-mi-lims-macbook-pro:pa2 ungmi$ as swap.s swap.s:16:Unknown pseudo-op: .type swap.s:16:Rest of line ignored. 1st junk character valued 115 (s). swap.s:19:suffix or operands invalid for `push' swap.s:46:suffix or operands invalid for `pop' ung-mi-lims-macbook-pro:pa2 ungmi$** and the source is .text .align 4 .globl swap .type swap,@function swap: pushl %ebp movl %esp, %ebp movl %ebp, %esp popl %ebp ret and I searched some solution which is I have to put -arch i386 than **ung-mi-lims-macbook-pro:pa2 ungmi$ as -arch i386 swap.s swap.s:16:Unknown pseudo-op: .type swap.s:16:Rest of line ignored. 1st junk character valued 115 (s). ung-mi-lims-macbook-pro:pa2 ungmi$** could you help me out.. just let me know what I need to compile assembly file.. I have xcode already.. and I'd rather to do this with commend window..and vi editor.. I will be waiting for your answer... plz help me.

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • Best way to store data in database when you don't know the type

    - by stiank81
    I have a table in my database that represents datafields in a custom form. The DataField gives some representation of what kind of control it should be represented with, and what value type it should take. Simplified you can say that I have 2 entities in this table - Textbox taking any string and Textbox only taking numbers. Now I have the different values stored in a separate table, referencing the datafield definition. What is the best way to store the data value here, when the type differs? One possible solution is to have the FieldValue table hold one field per possible value type. Now this would certainly be redundant, but at least I would get the value stored in its correct form - simplifying queries later. FieldValue ---------- Id DataFieldId IntValue DoubleValue BoolValue DataValue .. Another possibility is just storing everything as String, and casting this in the queries. I am using .Net with NHibernate, and I see that at least here there is a Projections.Cast that can be used to cast e.g. string to int in the query. Either way in these two solutions I need to know which type to use when doing the query, but I will know that from the DataField, so that won't be a problem. Anyway; I don't think any of these solutions sounds good. Are they? Or is there a better way?

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  • Embedded Office Application - How to know whether the app is running or the object is embedded

    - by A9S6
    I am adding an Excel Worksheet object inside Word. Excel has a COM addin attached to it. Any idea how one can know whether Excel is running independently or as an embedded object? The COM Addin attached to Excel loads when the embedded Excel object is activated (double-clicked) inside Word. I am looking for some kind of a property or a parameter in OnConnection(...) or other method that can tell the state of Excel object.

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  • How to know if two stocks move togheter?

    - by Damiano
    Hello, I have two stocks with their prices, example: STOCK1: 10.56 11.23 12.32 8.90 STOCK2: 1.26 5.80 3.26 10.3 I only found Pearson correlation, but, is there another method to know if two stocks move togheter? (esample: co-integration??) Thank you so much!

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  • To know is the object already retrieved in inject

    - by zerkms
    Is it possible to know that particular dependency already has been satisfied by ninject kernel? To be clear: Let's suppose we have this module: Bind<IA>().To<A>(); Bind<IB>().To<B>(); And some "client"-code: var a = kernel.Get<IA>(); // how to get here "true" for assumption: "IA was requested (once)" // and "false" for: "IB was not requested ever"

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