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• Why hasn't functional programming taken over yet?

  - by pankrax

  I've read some texts about declarative/functional programming (languages), tried out Haskell as well as written one myself. From what I've seen, functional programming has several advantages over the classical imperative style: Stateless programs; No side effects Concurrency; Plays extremely nice with the rising multi-core technology Programs are usually shorter and in some cases easier to read Productivity goes up (example: Erlang) Imperative programming is a very old paradigm (as far as I know) and possibly not suitable for the 21st century Why are companies using or programs written in functional languages still so "rare"? Why, when looking at the advantages of functional programming, are we still using imperative programming languages? Maybe it was too early for it in 1990, but today?

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• How can I manage a FIFO-queue in an database with SQL?

  - by Jonas

  I have two tables in my database, one for In and one for Out. They have two columns, Quantity and Price. How can I write a SQL-query that selects the correct price? In example: If I have 3 items in for 75 and then 3 items in for 80. Then I have two out for 75, and the third out should be for 75 (X) and the fourth out should be for 80 (Y). How can I write the price query for X and Y? They should use the price from the third and forth row. In example, is there any way to SELECT the third row in the In-table? I can not use auto_increment as identifier for i.e. "third" row, because the tables will contain post for other items too. The rows will not be deleted, they will be saved for accountability reasons. SELECT Price FROM In WHERE ...? NEW database design: +----+ | In | +----+------+-------+ | Supply_ID | Price | +-----------+-------+ | 1 | 75 | | 1 | 75 | | 1 | 75 | | 2 | 80 | | 2 | 80 | +-----------+-------+ +-----+ | Out | +-----+-------+-------+ | Delivery_ID | Price | +-------------+-------+ | 1 | 75 | | 1 | 75 | | 2 | X | <- ? | 3 | Y | <- ? +-------------+-------+ OLD database design: +----+ | In | +----+------+----------+-------+ | Supply_ID | Quantity | Price | +-----------+----------+-------+ | 1 | 3 | 75 | | 2 | 3 | 80 | +-----------+----------+-------+ +-----+ | Out | +-----+-------+----------+-------+ | Delivery_ID | Quantity | Price | +-------------+----------+-------+ | 1 | 2 | 75 | | 2 | 1 | X | <- ? | 3 | 1 | Y | <- ? +-------------+----------+-------+

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• How do I programmatically run all the JUnit tests in my Java application?

  - by Andrew McKinlay

  From Eclipse I can easily run all the JUnit tests in my application. I would like to be able to run the tests on target systems from the application jar, without Eclipse (or Ant or Maven or any other development tool). I can see how to run a specific test or suite from the command line. I could manually create a suite listing all the tests in my application, but that seems error prone - I'm sure at some point I'll create a test and forget to add it to the suite. The Eclipse JUnit plugin has a wizard to create a test suite, but for some reason it doesn't "see" my test classes. It may be looking for JUnit 3 tests, not JUnit 4 annotated tests. I could write a tool that would automatically create the suite by scanning the source files. Or I could write code so the application would scan it's own jar file for tests (either by naming convention or by looking for the @Test annotation). It seems like there should be an easier way. What am I missing?

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• Can someone recommend a good tutorial on MySQL indexes, specifically when used in an order by clause

  - by Philip Brocoum

  I could try to post and explain the exact query I'm trying to run, but I'm going by the old adage of, "give a man a fish and he'll eat for a day, teach a man to fish and he'll eat for the rest of his life." SQL optimization seems to be very query-specific, and even if you could solve this one particular query for me, I'm going to have to write many more queries in the future, and I'd like to be educated on how indexes work in general. Still, here's a quick description of my current problem. I have a query that joins three tables and runs in 0.2 seconds flat. Awesome. I add an "order by" clause and it runs in 4 minutes and 30 seconds. Sucky. I denormalize one table so there is one fewer join, add indexes everywhere, and now the query runs in... 20 minutes. What the hell? Finally, I don't use a join at all, but rather a subquery with "where id in (...) order by" and now it runs in 1.5 seconds. Pretty decent. What in God's name is going on? I feel like if I actually understood what indexes were doing I could write some really good SQL. Anybody know some good tutorials? Thanks!

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• Proper QUuid usage in Qt ? (7-Zip DLL usage problems (QLibrary, QUuid GUID conversion, interfaces))

  - by whipsnap

  Hi, I'm trying to write a program that would use 7-Zip DLL for reading files from inside archive files (7z, zip etc). Here's where I'm so far: #include QtCore/QCoreApplication #include QLibrary #include QUuid #include iostream using namespace std; #include "7z910/CPP/7zip/Archive/IArchive.h" #include "7z910/CPP/7zip/IStream.h" #include "MyCom.h" // {23170F69-40C1-278A-1000-000110070000} QUuid CLSID_CFormat7z(0x23170F69, 0x40C1, 0x278A, 0x10, 0x00, 0x00, 0x01, 0x10, 0x07, 0x00, 0x00); typedef int (*CreateObjectFunc)( const GUID *clsID, const GUID *interfaceID, void **outObject); void readFileInArchive() { QLibrary myLib("7z.dll"); CreateObjectFunc myFunction = (CreateObjectFunc)myLib.resolve("CreateObject"); if (myFunction == 0) { cout outArchive; myFunction(&CLSID_CFormat7z, &IID_IOutArchive, (void **)&outArchive); } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); readFileInArchive(); return a.exec(); } Trying to build that in Qt Creator will lead to following error: cannot convert 'QUuid*' to 'const GUID*' in argument passing How should QUuid be correctly used in this context? Also, being a C++ and Qt newbie I haven't yet quite grasped templates or interfaces, so overall I'm having trouble getting through these first steps. If someone could give tips or even example code on how for example an image file could be extracted from ZIP file (to be shown in Qt GUI later on*), I would highly appreciate that. My main goal at the moment is to write a program with GUI for selecting archive files containing image files (PNG, JPG etc) and displaying those files one at a time in the GUI. A Qt based CDisplayEx in short.

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• Load random swf object with jquery

  - by Eggnog

  I'm working on a site that utilizes full screen background video. I have three flash videos I'd like to load into the page which would be displayed randomly on page refresh. I know you can achieve this through action script loading the movies into one main .swf, but I'm rubbish with Flash and am looking for an alternative solution. My search so far has uncovered a method using jquery. Unfortunately my attempts to implement it have failed. I'm hoping someone more knowledgeable than myself can tell me if this technique is valid or what I'm doing wrong. Here's my code to date: <script type="text/javascript" src="files/js/swfobject.js"></script> <script type="text/javascript"> $(document).ready(function() { var sPath; var i = Math.floor(Math.random()*2); switch(i) { case 0: sPath = "flash/homepage_video.swf"; break; case 1: sPath = "flash/homepage_video.swf"; break; } // load the flash version of the image var so = new SWFObject(sPath, "flash-background", "100%", "100%"); so.addParam("scale", "exactFit"); so.addParam("movie", sPath); // NOTE: the sPath variable is also used here so.addParam("quality", "high"); so.addParam("wmode", "transparent"); so.write("homeBackground"); // NOTE: The value in this call to write() MUST match the name of the // HTML element (<div>) you're expecting the swf to show up in }); </script> <body> <div id="homeBackground"> <p>This is alternative content</p> </div> </body> I'm open to other suggestions that don't involve jquery (php perhaps). Thanks.

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• How can I use a compound condition in a join in Linq?

  - by Gary McGill

  Let's say I have a Customer table which has a PrimaryContactId field and a SecondaryContactId field. Both of these are foreign keys that reference the Contact table. For any given customer, either one or two contacts may be stored. In other words, PrimaryContactId can never be NULL, but SecondaryContactId can be NULL. If I drop my Customer and Contact tables onto the "Linq to SQL Classes" design surface, the class builder will spot the two FK relationships from the Customer table to the Contact table, and so the generated Customer class will have a Contact field and a Contact1 field (which I can rename to PrimaryContact and SecondaryContact to avoid confusion). Now suppose that I want to get details of all the contacts for a given set of customers. If there was always exactly one contact then I could write something like: from customer in customers join contact in contacts on customer.PrimaryContactId equals contact.id select ... ...which would be translated into something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id But, because I want to join on both the contact fields, I want the SQL to look something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id OR Customer.SecondSalesPersonId = Contact.id How can I write a Linq expression to do that?

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• Can one connection get details of another? Or, how can I get the most detailed pending transaction

  - by bob-the-destroyer

  Is there a Mysql statement which provides full details of any other open connection or user? For this particular case, on myisam tables specifically. Looking at Mysql's SHOW TABLE STATUS documentation, it's missing some very important information for my purpose. For example: remote odbc connection one is inserting several thousand records, which due to a slow connection speed can take up to an hour. Tcp connection two, using PHP on the server's localhost, is running select queries with aggregate functions on that data. Before allowing connection two to run those queries, I'd like connection two to first check to make sure there's no pending inserts on any other connection on those specific tables so it can instead wait until all data is available. If the table is currently being written to, I'd like to spit back to the user of connection two an approximation of how much longer to wait based on the number of pending inserts. Ideally by table, I'd like to get back using a query the timestamp when connection one began the write, total inserts left to be done, and total inserts already completed. Instead of insert counts, even knowing number of bytes written and left to write would work just fine here. Obviously since connection two is a tcp connection via a PHP script, all I can really use in that script is some sort of query. I suppose if I have to, since it is on localhost, I can exec() it if the only way is by a mysql command line option that outputs this info, but I'd rather not. I suppose I could simply update a custom-made transaction log before and after this massive insert task which the PHP script can check, but hopefully there's already a built-in Mysql feature I can take advantage of.

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• Need Help finding an appropriate task assignment algorithm for a college project involving coordinat

  - by Trif Mircea

  I am a long time lurker here and have found over time many answers regarding jquery and web development topics so I decided to ask a question of my own. This time I have to create a c++ project for college which should help manage the workflow of a company providing all kinds of services through in the field teams. The ideas I have so far are: client-server application; the server is a dispatcher where all the orders from clients get and the clients are mobile devices (PDAs) each team in the field having one a order from a client is a task. Each task is made up of a series of subtasks. You have a database with estimations on how long a task should take to complete you also know what tasks or subtasks each team on the field can perform based on what kind of specialists made up the team (not going to complicate the problem by adding needed materials, it is considered that if a member of a team can perform a subtask he has the stuff needed) Now knowing these factors, what would a good task assignment algorithm be? The criteria is: how many tasks can a team do, how many tasks they have in the queue, it could also be location, how far away are they from the place but I don't think I can implement that.. It needs to be efficient and also to adapt quickly is the human dispatcher manually assigns a task. Any help or leads would be really appreciated. Also I'm not 100% sure in the idea so if you have another way you would go about creating such an application please share, even if it just a quick outline. I have to write a theoretical part too so even if the ideas are far more complex that what i outlined that would be ok ; I'd write those and implement what I can. Edit: C++ is the only language I know unfortunately.

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• Matlab time stamps reading

  - by Paul

  Any easy way to read all the columns in Matlab? my format is date time y1 y2 y3 y4 ......................... 4/27/2010 00:3:09 34 45 45 56 ................ so on currently i am reading these with the code [c,pathc]=uigetfile({'*.txt'},'Select the data','C:\Data'); file=[pathc c]; data= dlmread(file, ',', 1,3); so needless to say i am skipping the time stamps. Was wondering if there is aeasy way to read the time stamps and plot my other colums agianst the time in hours. my files are 43200 X 30 and some are 86400 X 90 Related question : is the format same for .csv and .xls files , i mean except ofcourse xlsread

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• How to modify XML on Objective-C?

  - by Vic

  Hi, I'm working on a project for the iPad, I need to read and write to an xml file, which is also used by the counter part of the application in windows. The problem that I have is that I've been looking around but I haven't found a way to modify an element or attribute in an xml, without having to build the whole xml again. I saw this other post, which is basically the same problem that I have, and I also end it up in the same point as the person asking the question, NSXMLParser and TouchXML are read only and do not allowed me to modify my xml. Any other suggestion about what can I use? Thanks!

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• does entity framework or mysql provider swallows timeout exceptions on enumeration of result?!

  - by Freddy Rios

  I'm trying to make sense of a situation I have using entity framework on .net 3.5 sp1 + MySQL 6.1.2.0 as the provider. It involves the following code: Response.Write("Products: " + plist.Count() + "<br />"); var total = 0; foreach (var p in plist) { //... some actions total++; //... other actions } Response.Write("Total Products Checked: " + total + "<br />"); Basically the total products is varying on each run, and it isn't matching the full total in plist. Its varies widely, from ~ 1/5th to half. There isn't any control flow code inside the foreach i.e. no break, continue, try/catch, conditions around total++, anything that could affect the count. As confirmation, there are other totals captured inside the loop related to the actions, and those match the lower and higher total runs. I don't find any reason to the above, other than something in entity framework or the mysql provider that causes it to end the foreach when retrieving an item. The body of the foreach can have some good variation in time, as the actions involve file & network access, my best shot at the time is that when it takes beyond certain threshold there is some type of timeout in the underlying framework/provider and instead of causing an exception it is silently reporting no more items for enumeration. Can anyone give some light in the above scenario and/or confirm if the entity framework/mysql provider has the above behavior?

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• Implicit conversion between Scala collection types

  - by ebruchez

  I would like to implicitly convert between the Scala XML Elem object and another representation of an XML element, in my case dom4j Element. I wrote the following implicit conversions: implicit def elemToElement(e: Elem): Element = ... do conversion here ... implicit def elementToElem(e: Element): Elem = ... do conversion here ... So far so good, this works. Now I also need collections of said elements to convert both ways. First, do I absolutely need to write additional conversion methods? Things didn't seem to work if I didn't. I tried to write the following: implicit def elemTToElementT(t: Traversable[Elem]) = t map (elemToElement(_)) implicit def elementTToElemT(t: Traversable[Element]) = t map (elementToElem(_)) This doesn't look too ideal because if the conversion method takes a Traversable, then it also returns a Traversable. If I pass a List, I also get a Traversable out. So I assume the conversion should be parametrized somehow. So what's the standard way of writing these conversions in order to be as generic as possible?

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• Why does Firefox + My code Destroys FireFox refresh

  - by acidzombie24

  I am soo angry right now. I lost hours and i dont know why this happens. Its a semi rant but i'll try to keep it short My code would not work, even after refreshing it was broken I fixed my code or so i thought because it stops working without me changing anything (you would think i am imagining this...) I somehow decide to make a new window or tab i run my code and verifies it works. I write more code and see everything is broken again I write test in a new window and see my code does work I see my code doesnt work and firebug DOES NOT HELP I notice when i create a new tab everything works I realize refreshing does not work and i MUST make a new tab for my code to work. Then i knew instantly what the problem was. I modify a display:none textbox but i set the values incorrectly. I cant see it because it is hidden. Now some of you might say its my fault because when doing a refresh all of the data may be cache. But here is the kicker. I was using POST data. I posted in between of the refresh each and everytime. Whats the point of using POST when the same data is cached and use anyways? If theres no chance for a search engine to follow a block user get link then why should i bother making anything post when security or repeat actions are not an issue? POST didnt seem to do anything.

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• ProtoBuffers, sending the protoobjects over the network

  - by Faisal Abid

  My webservice(in java) will generate ProtoBuffer objects, how do i send this across so that my Python script can read the protobuffer object?

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• In a Linux user space process what is the address of the vsyscall page?

  - by TomMD

  I would like to acquire the address of the vsyscall page for my own uses. I only have two ideas here: alter the compiler to store this information in some known location after it is given to __start, or read /proc/[pid]/maps. I really don't want to read /proc/ as that is slow and shouldn't be necessary. I also don't want to make compiler modifications. Does anyone have an alternative? Is there a symbol I should know about? Its at the point I'm tempted to stuff this functionality into an ioctl call in a module I've developed as part of this work!

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• SQL Server Mapping a user to a login and adding roles programmatically

  - by user163457

  In my SQL Server 2005 server I create databases and logins using Management Studio. My application requires that I give a newly created user read and write permissions to another database. To do this I right-click the newly created login, select properties and go to User Mapping. I put a check beside the database to map this login to the db and select db_datareader and db_datawriter as the roles to map. Can this be done programmatically? I've read about using Alter User and sp_change_users_login but I'm having problems getting these to work, since sp_change_users_login has been deprecated so I'd prefer to use Alter User. Please note my understanding of SQL Server database users/logins/roles is basic

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• Q on filestream and streamreader unicode

  - by habbo95

  HI all of u,, I have big problem until now no body helped me. firstly I want to open XXX.vmg (this extension come from Nokia PC Suite) file and read it then write it in richtextbox. I wrote the code there is no error and also there is no reault in the richtextbox here is my code FileStream file = new FileStream("c:\\XXX.vmg", FileMode.OpenOrCreate, FileAccess.Read); StreamWriter sw = new StreamWriter(fileW); StreamReader sr = new StreamReader(file); string s1 = sr.ReadToEnd(); string[] words = s1.Split(' '); for (int i=0; i<words.length; i++) richTextBox1.Text +=Envirment.NewLine + words[i]; The output at richtextbox just blank line

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• C++ - how does Sleep() and cin work?

  - by quano

  Just curious. How does actually the function Sleep() work (declared in windows.h)? Maybe not just that implementation, but anyone. With that I mean - how is it implemented? How can it make the code "stop" for a specific time? Also curious about how cin and those actually work. What do they do exactly? The only way I know how to "block" something from continuing to run is with a while loop, but considering that that takes a huge amount of processing power in comparison to what's happening when you're invoking methods to read from stdin (just compare a while (true) to a read from stdin), I'm guessing that isn't what they do.

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• Extracting DCT coefficients from encoded images and video

  - by misha

  Is there a way to easily extract the DCT coefficients (and quantization parameters) from encoded images and video? Any decoder software must be using them to decode block-DCT encoded images and video. So I'm pretty sure the decoder knows what they are. Is there a way to expose them to whomever is using the decoder? I'm implementing some video quality assessment algorithms that work directly in the DCT domain. Currently, the majority of my code uses OpenCV, so it would be great if anyone knows of a solution using that framework. I don't mind using other libraries (perhaps libjpeg, but that seems to be for still images only), but my primary concern is to do as little format-specific work as possible (I don't want to reinvent the wheel and write my own decoders). I want to be able to open any video/image (H.264, MPEG, JPEG, etc) that OpenCV can open, and if it's block DCT-encoded, to get the DCT coefficients. In the worst case, I know that I can write up my own block DCT code, run the decompressed frames/images through it and then I'd be back in the DCT domain. That's hardly an elegant solution, and I hope I can do better. Presently, I use the fairly common OpenCV boilerplate to open images: IplImage *image = cvLoadImage(filename); // Run quality assessment metric The code I'm using for video is equally trivial: CvCapture *capture = cvCaptureFromAVI(filename); while (cvGrabFrame(capture)) { IplImage *frame = cvRetrieveFrame(capture); // Run quality assessment metric on frame } cvReleaseCapture(&capture); In both cases, I get a 3-channel IplImage in BGR format. Is there any way I can get the DCT coefficients as well?

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• Haskell: reading multiple command line arguments

  - by Survot

  Hi all, Okay, so I am making a program in Haskell that needs to change certain words based on two command line arguments. I have made the replace function and everything works great, but I am stumped getting it to work with command line arguments. Here is the main code: (replace function not included) main = do text <- getContents (command1:command2:_) <- getArgs putStrLn (replace (read command1) (read command2) text) So for intstance in the terminal I want to be able to type something like: "--- cat textfile.txt | ./replace oldword newword" I know this code is close since I have seen others do it this way. O_o Thanks for any help

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• Using input type="submit" to change content

  - by Conti

  Okay, I'm pretty sure I'm missing something very obvious here, but I just couldn't find a proper solution so far. What I'm trying to do is simple: Have a user write something into a form, have him submit the form, and write that input into a textarea on the same page. This is my code: <html><head></head> <body> <form name='registration'> <label for="input">Input:</label> <input type="text" id="input"/> <input type="submit" id="submit" value="Submit" onclick="execute()"/> </form> <div id="results"> <span>Result</span> <span><textarea cols="30" rows="5" id="resulttext" readonly="readonly"></textarea> </span> </div> <script> function execute() { var result = document.getElementById("input").value document.getElementById("resulttext").value=result; } </script> </body> </html> Now what happens if I enter something into the form is that the textarea briefly shows my input before reverting back to showing nothing. My guess is that the textarea field is only changed for the duration of the execute() function. When I change input type="submit" to a <button> everything works as intended, but I'm pretty sure I'm not supposed to do that.

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• reading and writing QByteArrays

  - by synchronicity

  I'm having trouble reading and writing QByteArray data to a file. My goal is to save QPixmap data into a QByteArray and save that QByteArray to a file (with the ability to read this QByteArray back from the file and into a QPixmap). I want to use following code from the QPixmap documentation: QPixmap pixmap(<image path>); QByteArray bytes; QBuffer buffer(&bytes); buffer.open(QIODevice::WriteOnly); pixmap.save(&buffer, "PNG"); // writes pixmap into bytes in PNG format After writing the buffer to a file, I want to be able to retrieve the QByteArray and load it back into a QPixmap using the QPixmap::loadFromData() function. Please let me know if any further clarification is needed (I'm open to alternative approaches as well, I just need to be able to read and write the QPixmap to a file! :) );

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• Alternatives libraries for loading PNG images

  - by Robert

  My java J2SE application is reading a lot of (png) images from the web and some of them use features such as a transparency color for true-color images (tRNS section) that Sun's/Oracle's PNGImageReader implementation simply ignores. Therefore the common solution for loading via ImageIO.read(...); does not work for me as it relies on this incomplete PNGImageReader implementation. Does anybody know a png reader implementation that can read all forms of PNG images correctly - those with color table or true-color and alpha transparency or transparent color? As it is for a GPL project it should be a non-commercial one that can be included without licensing problems into the app. Edit: My be this question was too specific. Therefore let be redesign my question: Who knows alternative implementations and libraries that are able to load PNG files? I will then test the implementations for their capabilities to load some test png images. Edit2: The end result have to be a BufferedImage

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• Append data to same text file

  - by Manu

  SimpleDateFormat formatter = new SimpleDateFormat("ddMMyyyy_HHmmSS"); String strCurrDate = formatter.format(new java.util.Date()); String strfileNm = "Customer_" + strCurrDate + ".txt"; String strFileGenLoc = strFileLocation + "/" + strfileNm; String Query1="select '0'||to_char(sysdate,'YYYYMMDD')||'123456789' class_code from dual"; String Query2="select '0'||to_char(sysdate,'YYYYMMDD')||'123456789' class_code from dual"; try { Statement stmt = null; ResultSet rs = null; Statement stmt1 = null; ResultSet rs1 = null; stmt = conn.createStatement(); stmt1 = conn.createStatement(); rs = stmt.executeQuery(Query1); rs1 = stmt1.executeQuery(Query2); File f = new File(strFileGenLoc); OutputStream os = (OutputStream)new FileOutputStream(f,true); String encoding = "UTF8"; OutputStreamWriter osw = new OutputStreamWriter(os, encoding); BufferedWriter bw = new BufferedWriter(osw); while (rs.next() ) { bw.write(rs.getString(1)==null? "":rs.getString(1)); bw.write(" "); } bw.flush(); bw.close(); } catch (Exception e) { System.out.println( "Exception occured while getting resultset by the query"); e.printStackTrace(); } finally { try { if (conn != null) { System.out.println("Closing the connection" + conn); conn.close(); } } catch (SQLException e) { System.out.println( "Exception occured while closing the connection"); e.printStackTrace(); } } return objArrayListValue; } The above code is working fine. it writes the content of "rs" resultset data in text file Now what i want is ,i need to append the the content in "rs2" resultset to the "same text file"(ie . i need to append "rs2" content with "rs" content in the same text file)..

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