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  • PreparedStatement throws MySQLSyntaxErrorException

    - by sqlBugs
    I have the following Java code: String query = "Select 1 from myTable where name = ? and age = ?"; PreparedStatement stmt = conn.prepareStatement(query); stmt.setString(1, name); stmt.setInt(2, age); ResultSet rs = stmt.executeQuery(); Whenever I run the above code, it throws an exception on line 2 (where the PreparedStatement is declared): Error 0221202: SQLException = com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '? AND age = ?' at line 1 Does anyone have any suggestions about what I am doing wrong? Thanks!

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  • MVC Framework for existing application.

    - by Dhruva
    I am modifying existing java web application that was written long time ago, and it is written in the wrost possible way. It has business logic and sql statemens in JSP files. Because of the certain constraint, I can not re-design the entire application. but I can implement better design in any new feature that I add. can anybody suggest me any MVC framework that I could easily integrate in existing app. I need to have framework that is not depended on many external jar files and it does not cause any issues with existing application.

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  • Selecting item from set given distribution

    - by JH
    I have a set of X items such as {blower, mower, stove} and each item has a certain percentage of times it should be selected from the overall set {blower=25%,mower=25%,stove=75%} along with a certain distribution that these items should follow (blower should be selected more at the beginning of selection and stove more at the end). We are given a number of objects to be overall selected (ie 100) and a overall time to do this in (say 100 seconds). I was thinking of using a roulette wheel algorithm where the weights on the wheel are affected by the current distribution as a function of the elapsed time (and the allowed duration) so that simple functions could be used to determine the weight. Are there any common approaches to problems like this that anyone is aware of? Currently i have programmed something similar to this in java using functions such as x^2 (with correct normalization for the weights) to ensure that a good distribution occurs. Other suggestions or common practices would be welcome :-)

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  • Does this game have a solution

    - by Bragboy
    Hi, I am developing a simple game using Java swing. I want to know whether this particular game has a solution in the following scenario. If I am convinced that theoretically a solution cannot be arrived at this point, I will throw a notification to the user. 3x3 4x4 The objective of this game is to fill numbers from 1 to 8 (or 1 to 15) using the one space available to push the numbers to that empty space. Every time I end up with the combination shown above. I just want to convince myself that there is no way to attain the proper solution from the above scenario. Please help. EDIT : Solution has been posted at here and here

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  • Is there an automatic way to remove debugging methods for a release build?

    - by Lewis
    Note: This is an extension of an earlier question I asked here: Do additional function/method definitions increase a program's memory footprint? When I write a class, I usually end up writing several testing/debugging methods, used to make sure the class works as it should, or for printing data to help with debugging, or for unit testing, etc. Is there an easy/automatic way to make a release without these methods, or do I need to manually delete the extra code any time I want to compile a release version? I ask this question both from a C++ and a Java perspective. I'm using Code::Blocks and Eclipse as IDEs, if that plays into the answer somehow.

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  • How to continue copying on error with copyDirectory from FileUtils (Apache Commons IO 2.4)

    - by Exocom
    I am trying to copy files from one folder to another using the FileUtils method "static void copyDirectory(File srcDir, File destDir)" from apache commons io (2.4) with the following code: String srcDir = "/sourceDirectory/examples/"; String destDir = "/tmp/examples/"; try{ FileUtils.copyDirectory(new File(srcDir), new File(destDir)); } catch (IOException e){ e.printStackTrace(); } The file structure looks like the following: examples/ (read access) examples/.subdirectory (NO access) examples/file1.txt (read access) examples/file2.txt (read access) examples/subdirectory2/file1.txt (read access) examples/subdirectory2/file2.txt (NO access) The problem is, that in srcDir there are a few files and one subdirectory I don't have access to. FileUtils.copyDirectory throws an "java.io.FileNotFoundException: .subdirectory (Permission denied)" and aborts. Is it possible to ignore those files I don't have permission to and just copy all the other files I can read?

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  • Problems opening large csv file

    - by John Tyler
    I have a csv file that is 100mb in size. I need to parse some data out of it into a new format. I tried PHP, but keep running into memory issues. After around the first 150 "rows" or so, the script poops out. This is even on the localhost, and doing everything I can to tune the PHP settings, including max_memory and script_execution_time. Now before I continue, I'd like to know if Python will poop out on me too. Or if I will have to use C++. Can someone name good csv libraries for for these programmin langueage? The file is quoted csv. I mean scheiza I can't even open this text file in OpenOffice without it dying on me. (then again, Java sux as bad as PHP)

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  • Adapting methods which return true/false

    - by James P.
    What's the best practise when adapting C-style functions which return a true/false to Java? Here's a simple method to illustrate where the problem lies. public static boolean fileNameEndsWithExtension( String filename, String fileExtension) { return filename.endsWith( fileExtension ); } Note that there's probably a more elegant way of filtering files (feel free to comment on this). Anyway, if filename is a null value, does one: Return a false if filename is null? If so, how does one go about distinguishing between the case where filename is null and the case where the String or file name doesn't end with a given file extension? Change the return type to the wrapper class Boolean which allows a null value. Throw an Exception and force the programmer to make sure that a null value is never passed to the method? Use another solution?

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  • Solr adding document cycle & wait on response issue

    - by user1585896
    I am trying to send http post request to Solr for adding 50000 documents (all individual request one after another in while loop). I am using DefaultHttpClient in java to connect to Solr and when I use execute method on my HttpPost Solr takes 3 to 4 ms to response. I have commit=false, autoCommit=false, autoSoftCommit=false. My question is why it takes that much time to response and why cycle it follows to add new document. Basically I want to send add request but do not want to commit to see how many request can Solr handle without doing any kind of commits(without having to do any disk access). My guess is with above parameter tuned off I should be hitting Solr about 10000 times every second, but my result is 300 times a second. I am generating random data to add in my code.

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  • JBoss, exploded jar vs compact jar.

    - by Win Man
    Hi, I am working on Java 1.6, JBoss 5.1, EJB 3, and Hibernate 2. Every time I deploy the ear, if the jar is a compact one (non-exploded), application doesn't work. However when I explode the jar and then add it to the ear, the app works fine. Tried restarting Jboss, doesn't help. The ear refers to numerous external jars; would the order of loading the jars be an issue? How can I make JBoss load external jars followed by the app jars? Thx. WM.

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  • How to double the size of 8x8 Grid whilst keeping the relative position of certain tiles intact?

    - by ke3pup
    Hi guys I have grid size of size 8x8 , total of 64 Tiles. i'm using this Grid to implement java search algorithms such as BFS and DFS. The Grid has given forbidden Tiles (meaning they can't be traversed or be neighbour of any other tile) and Goal and Start tile. for example Tile 19,20,21,22 and 35, 39 are forbidden and 14 an 43 are the Goal and start node when the program runs. My question is , How can i double the size of the grid, to 16x16 whilst keeping the Relative position of forbidden tiles as well as the Relative position of start and goal Tiles intact? On paper i know i can do this by adding 4 rows and columns to all size but in coding terms i don't know how to make it work? Can someone please give any sort of hints?

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  • How to analyse Dalvik GC behaviour?

    - by HRJ
    I am developing an application on Android. It is a long running application that continuously processes sensor data. While running the application I see a lot of GC messages in the logcat; about one every second. This is most probably because of objects being created and immediately de-referenced in a loop. How do I find which objects are being created and released immediately? All the java heap analysis tools that I have tried(*) are bothered with the counts and sizes of objects on the heap. While they are useful, I am more interested in finding out the site where temporary short-lived objects get created the most. (*) I tried jcat and Eclipse MAT. I couldn't get hat to work on the Android heap-dumps; it complained of an unsupported dump file version.

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  • lookahead and group

    - by Istao
    Hi, In Java, on a text like foo <on> bar </on> thing <on> again</on> now, I should want a regex with groups wich give me with a find "foo", "bar", empty string, then "thing", "again", "now". If I do (.*?)<on>(.*?)</on>(?!<on>), I get only two group (foo bar, thing again, and I've not the end "now"). if I do (.*?)<on>(.*?)</on>((?!<on>)) I get foo bar empty string, then thing again and empty string (here I should want "now"). Please what is the magical formula ? Thanks.

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  • Returning back to the results after editing

    - by Parhs
    Hello, I am developing an application which has several CRUD actions... I am using Java and i am forced to use Struts framework. My problem is: I have a search page which returns some results.The user can click at a result and then he goes to another edit-page... He may apply changes or not...What i need is a way to return at the result page again and at the same scroll position.Javascript must be enabled for this project however.. I am wondering which is the best practice to achieve this effect... A solution would be to save the last search URL but i know that this wouldnt work if the user has multiple results. I know how to do it but i am lloking for a good practice!

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  • Can I write to different jetty databases using JPA that is using the same "entity class"

    - by Per
    I am using Java persistance and there EntityManager class and have it assigned to storage a class object that shall be written to the database. My problem is that I want to write to different databases using the same storage class. My solution to that was to write a StorageManagerfactory that has a Map holding all EntityManagers. The solution looked good until I looked at the databases and realized that all information (undepending of the Map, which gets the correct value) was written to the same database (one of the initialised in the Map). So my question is: Can I write to different databases using JPA that is using the same storage class (the class holding the structure of my database)? Thanks

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  • Need help on how to setup my packages and projects in eclipse

    - by jax
    I am new to Java and am making a license generator. This is my current setup. com.example.licensegenerator.client (used by the client application) :LicenseLoader (no Main method) :LicenseDownloader (no Main method) com.example.licensegenerator.server.keys (used by the server) :ProductKeyGenerator(Main method) com.example.licensegenerator.server.license (used on the server also) :LicenseGenerator(Main method) com.example.licensegenerator.lib (Shared classes between client and server) :Contants (no main) Now I have a few questions. Is it OK to have multiple Main() methods in a single project? Will I be able to compile them to different .jar files? (In this case I need two different jars for the server) Is there a better way to setup the packages? And a totally unrelated question, with exceptions, is it better to handle them right then and there or throw them and let the main method catch them all (the program cannot recover if an error occurs)

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  • What happens to an instance of ServerSocket blocked inside accept(), when I drop all references to i

    - by Hanno Fietz
    In a multithreaded Java application, I just tracked down a strange-looking bug, realizing that what seemed to be happening was this: one of my objects was storing a reference to an instance of ServerSocket on startup, one thread would, in its main loop in run(), call accept() on the socket while the socket was still waiting for a connection, another thread would try to restart the component under some conditions, the restart process missed the cleanup sequence before it reached the initialization sequence as a result, the reference to the socket was overwritten with a new instance, which then wasn't able to bind() anymore the socket which was blocking inside the accept() wasn't accessible anymore, leaving a complete shutdown and restart of the application as the only way to get rid of it. Which leaves me wondering: with no references left to the ServerSocket instance, what would free the socket for a new connection? At what point would the ServerSocket become garbage collected? In general, what are good practices I can follow to avoid this type of bug?

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  • Understanding flow of object creation

    - by Boris Mandovskes
    I'm new to java and I wonder if there is simple way to know flow like the following of object creation, I'm using eclipse and when I write new ObjectInputStream and press CTRL+SPACE. I don't see any option that I can enter new BufferedInputStream (I have copied the code from example) and than to create new object for FileInputStream etc. in = new ObjectInputStream(new BufferedInputStream(new FileInputStream("emp.dat"))); List temp = (List)in.readObject(); I give that example since this is the first time that I saw this kind of creation new object flow and I want to use some best practice for the next times.

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  • HTML J2ME Problem

    - by Hesham
    i'm trying to put large amount of data in a java me application for a BlackBerry mobile and i noticed that the max file size to be accepted in BlackBerry is 150 KB, by the way i'm developping the application in arabic language so i'm converting every litter to his corresponding unicode so every char gets to 6 chars so its another big problem, some ppl told me that i can write arabic as arabic letters without the need to write its unicode, by viewing the mobile form as an html page, my problem is that i dont know how to view the page as html page and what is XMLParser ?? can anyone help me to get all this together, cos i really need some serious help thank you alot Hesham

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  • Need help: input int from console and pass it into method in different class

    - by christophe
    i'm a beginner, Need help, Please!!! I want to read number "a" from console and then store them in variable to use as passing to a different class (different .java file). How do i code the 2 classes? thanks public class PassedInMethod{ private int a; . public PAssMethod(int a) { a = a; // TODO: where to get the a? System.out.println("a was passed in!"+a); } public class Mainclass{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); int a; System.out.print( "Enter your nember: " ); a = input.nextInt(); PassedInMethod(int a); }

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  • getting started with qpid server

    - by London
    I'd like to get started with qpid, can anyone recommend some useful resources/links/code examples for me to study? I'm interested about java implementations?I'd like to create message sender/listener. I've already done messaging with jboss where I send the message to the queue and the listener picks it up from there, what is different with qpid? Is it the same only replacing jboss as a server with qpid or?I'm new to all of this it might sound weird when I ask it. Oh yes similar question: http://stackoverflow.com/questions/1693099/get-started-with-qpid Doesn't really help me much. Any hints would help me a lot. thank you

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  • How to acquire the Context in an Adobe AIR Native Extension?

    - by rotaercz
    In the following line of code... ProgressDialog progressDialog = ProgressDialog.show(getBaseContext(), "LOADING_TITLE", "LOADING_MESSAGE"); In place of getBaseContext() I've tried... getApplicationContext() this NativeActivity.this (NativeActivity)getApplicationContext() Among others. I'm not sure why it's not working. In the NativeExtensionContext which extends FREContext I am passing the activity using getActivity() to NativeActivity. Everything works well but I get a "Nullpointerexception" or “android.view.WindowManager$BadTokenException: Unable to add window — token null is not for an application” when I try I try to get a reference to the Context. Anyone with experience using Adobe AIR Native Extensions and/or Android Java would be great.

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  • FileInputStream and FileOutputStream to the same file: Is a read() guaranteed to see all write()s that "happened before"?

    - by user946850
    I am using a file as a cache for big data. One thread writes to it sequentially, another thread reads it sequentially. Can I be sure that all data that has been written (by write()) in one thread can be read() from another thread, assuming a proper "happens-before" relationship in terms of the Java memory model? Is this behavior documented? EDIT: In my JDK, FileOutputSream does not override flush(), and OutputStream.flush() is empty. That's why I'm wondering... EDIT^2: The streams in question are owned exclusively by a class that I have full control of. Each stream is guaranteed to be accesses by one thread only. My tests show that it works as expected, but I'm still wondering if this is guaranteed and documented. See also this related discussion: http://chat.stackoverflow.com/rooms/17598/discussion-between-hussain-al-mutawa-and-user946850

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  • How to Get the Method/Function Call Trace for a Specific Run?

    - by JackWM
    Given a Java or JavaScript program, after its execution, print out a sequence of calls. The calls are in invocation order. E.g. main() { A(); } A() { B(); C(); } Then the call trace should be: main -> A() -> B() -> C() Is there any tool that can profile and output this kind of information? It seems this is common a need for debugging or performance tuning. I noticed that some profilers can do this, but I prefer a simpler/easy-to-use one. Thanks!

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  • Android: Prompt user to save changes when Back button is pressed

    - by chriskopec
    I have an activity that contains several user editable items (an EditText field, RatingBar, etc). I'd like to prompt the user if the back/home button is pressed and changes have been made that have not yet been saved. After reading through the android documentation, it seems like this piece of code should go in the onPause method. I've tried putting an AlertDialog in the onPause however the dialog gets shown and then immediately tears down because nothing is there to block the pause from completing. This is what I've come up with so far: @Override protected void onPause() { super.onPause(); AlertDialog ad = new AlertDialog.Builder(this).setMessage( R.string.rating_exit_message).setTitle( R.string.rating_exit_title).setCancelable(false) .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { // User selects OK, save changes to db } }).setNeutralButton(android.R.string.cancel, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { // User selects Cancel, discard all changes } }).show(); } Am I on the right track or is there another way to accomplish what I'm trying to do here? Any help would be great!

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