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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • select multiple double side

    - by Mercer
    hello, i want to do a select multiple double side like this : http://www.senamion.com/blog/jmultiselect2side.html (Demo2) but i don't know how i can retrieve my data when i click submit button..?

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  • Swing invokeLater never shows up, invokeAndWait throws error. What can I do?

    - by Geo
    I have this code: try { SwingUtilities.invokeAndWait(new Runnable() { public void run() { try { dialog.handleDownload(); } catch (IOException io) { io.printStackTrace(); } } }); } catch(Exception io) { io.printStackTrace(); } in the handleDownload I'm reading an inputstream, calculating a progress bar's value, and setting it to that. So, when I click a button, a new JFrame opens up and does all the stuff I wrote above. If I have the dialog.handleDownload by itself ( in no SwingUtilities method ), it freezes until the operation is finished. If I add it in a invokeLater it's closed very fast ( I can't see anything, and the operation is not finished ). If I add it in a invokeAndWait I get the invokeAndWait cannot be called from the event dispatcher thread error. What should I do?

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  • Streaming large result sets with MySQL

    - by configurator
    I'm developing a spring application that uses large MySQL tables. When loading large tables, I get an OutOfMemoryException, since the driver tries to load the entire table into application memory. I tried using statement.setFetchSize(Integer.MIN_VALUE); but then every ResultSet I open hangs on close(); looking online I found that that happens because it tries loading any unread rows before closing the ResultSet, but that is not the case since I do this: ResultSet existingRecords = getTableData(tablename); try { while (existingRecords.next()) { // ... } } finally { existingRecords.close(); // this line is hanging, and there was no exception in the try clause } The hangs happen for small tables (3 rows) as well, and if I don't close the RecordSet (which happened in one method) then connection.close() hangs.

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  • SOAP logging axis2

    - by salcin
    Using axis1 it is possible to log incoming/outgoing soap messages by adding logging on HTTPSender in log4j.properties. After migrating to axis2 (version 1.4.1) I have a hard time figuring out how to accomplish the same kind of logging. I have tried to add logging on the axis2 package and org.apache.commons.httpclient but no logging is provided. Any ideas? TIA

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  • Determining if an offset is in between line numbers?

    - by Sophomore
    hi I need to determine if a given selection is in between a start line and an end line. I have an ILineRange and a given offset within the viewport of eclipse. (I need to know, if the selection (from a remote party) was made within the current viewport of the local user. Unfortunately, I cannot get an LineRange from the selection. I must rely on getOffset() and getLength()... Anyone has an idea? I think there is not a clean solution for this, as the offset (or the characters per line vary (new line lines or a big block of comment).

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  • Reset JPA generated value between tests

    - by Rythmic
    I'm running spring + hibernate + JUnit with springJunit4runner and transactional set to default rollback I'm using in-memory derbydb as Database. Hibernate is used as a JPA Provider and I am successfully testing CRUD kinds of stuff. However, I have a problem with JPA and the behaviour of @GeneratedValue If I run one of my tests in isolation, two entitys are persisted with id 1 and 2. If i run the whole test suite the ids are instead 6 and 7. Spring does rollbacks just fine so there are only these two entitys in the database after addition and of course zero before. But behaviour of @GeneratedValue doesn't allow me to reliable findById unless I would return the Id from the dao.add(Entity e) //method I don't feel like doing that for the sake of testing, or is it a good practise to return the entity that was persisted so I should be doing it anyway?

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  • How to create an ARGB_8888 pixel value?

    - by vidstige
    Say I want to create an array of pixel values to pass into the createBitmap method described here. I have three int values r, g, b in the range 0 - 0xff. How do I transform those into a opaque pixel p? Does the alpha channel go in the high byte or the low byte? I googled up the documentation but it only states that: Each pixel is stored on 4 bytes. Each channel (RGB and alpha for translucency) is stored with 8 bits of precision (256 possible values.) This configuration is very flexible and offers the best quality. It should be used whenever possible. So, how to write this method? int createPixel(int r, int g, int b) { retrurn ? }

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  • Storing Result set into an array

    - by OVERTONE
    i know this should be simpel and im probably staring straight at the problem but once again im stuck and need the help of the code gurus. im trying too take one row from a column in jdbc, and put them in an array. i do this as follows: public void fillContactList() { createConnection(); try { Statement stmt = conn.createStatement(); ResultSet namesList = stmt.executeQuery("SELECT name FROM Users"); try { while (namesList.next()) { contactListNames[1] = namesList.getString(1); System.out.println("" + contactListNames[1]); } } catch(SQLException q) { } conn.commit(); stmt.close(); conn.close(); } catch(SQLException e) { } creatConnection is an already defined method that does what it obviously does. i creat my result set while theres another one, i store the string of that column into an array. then print it out for good measure. too make sure its there. the problem is that its storing the entire column into contactListNames[1] i wanted to make it store column1 row 1 into [1] then column 1 row 2 into [2] i know i could do this with a loop. but i dont know too take only one row at a time from a single column. any ideas? p.s ive read the api, i jsut cant see anything that fits.

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  • MySQL Connection Error with JSP

    - by voidmain
    Hello, I am trying to connect to mysql database from jsp page. The connection code is as below InitialContext ic=new InitialContext(); DataSource ds=(DataSource)ic.lookup("jdbc:mysql://localhost:3306/"); Connection con=ds.getConnection(); Statement stmt = con.createStatement(); when i open the page i get the following error javax.servlet.ServletException: javax.naming.NamingException: Lookup failed for 'jdbc:mysql://localhost:3306/' in SerialContext [Root exception is javax.naming.NameNotFoundException: jdbc:mysql:] can some one please tell me what is wrong with this...

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  • Reading http file on url

    - by Nkunzis
    I am trying to read an xml file on an http url. "Unexpected end of file from server" keeps on coming . the page is password protected, I would like to know if I am properly giving in my url authentication details. I tried with non protected pages and I can read them properly. Here is my code: URL url = new URL("http://username:[email protected]:0000/test.xml"); URLConnection yc = url.openConnection(); BufferedReader in = new BufferedReader(new InputStreamReader(yc.getInputStream())); String inputLine; while ((inputLine = in.readLine()) != null) System.out.println(inputLine); in.close();

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  • Modular Inverse and BigInteger division

    - by dano82
    I've been working on the problem of calculating the modular inverse of an large integer i.e. a^-1 mod n. and have been using BigInteger's built in function modInverse to check my work. I've coded the algorithm as shown in The Handbook of Applied Cryptography by Menezes, et al. Unfortunately for me, I do not get the correct outcome for all integers. My thinking is that the line q = a.divide(b) is my problem as the divide function is not well documented (IMO)(my code suffers similarly). Does BigInteger.divide(val) round or truncate? My assumption is truncation since the docs say that it mimics int's behavior. Any other insights are appreciated. This is the code that I have been working with: private static BigInteger modInverse(BigInteger a, BigInteger b) throws ArithmeticException { //make sure a >= b if (a.compareTo(b) < 0) { BigInteger temp = a; a = b; b = temp; } //trivial case: b = 0 => a^-1 = 1 if (b.equals(BigInteger.ZERO)) { return BigInteger.ONE; } //all other cases BigInteger x2 = BigInteger.ONE; BigInteger x1 = BigInteger.ZERO; BigInteger y2 = BigInteger.ZERO; BigInteger y1 = BigInteger.ONE; BigInteger x, y, q, r; while (b.compareTo(BigInteger.ZERO) == 1) { q = a.divide(b); r = a.subtract(q.multiply(b)); x = x2.subtract(q.multiply(x1)); y = y2.subtract(q.multiply(y1)); a = b; b = r; x2 = x1; x1 = x; y2 = y1; y1 = y; } if (!a.equals(BigInteger.ONE)) throw new ArithmeticException("a and n are not coprime"); return x2; }

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  • Android: Alignment of four squares

    - by metter
    Hello There I am trying to align four equally sized squares on an Android Screen & I have now tried what feels like a million different approaches, yet none of them seem to work :(. What I've got at the moment is the following: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/MasterLayout" android:layout_width="wrap_content" android:layout_height="fill_parent" android:background="#FFFFFF" <TableRow android:layout_weight="1" android:background="#BBBBBB" android:padding="0dip"> <TableRow android:layout_weight="1" android:padding="0dip"> This basically does the job. However, every one of those four Images has a huge padding above and under it. How do I get rid of that? Or do I need to use a different Layout type alltogether? To help illustrate my problem, here's a picture. On the left is what I got, on the right is what I need. Image Thank you very much! Cheers, Markus!

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  • Io exception: There is no process to read data written to a pipe.

    - by Srikanth
    I'm using Hibernate3.2+Websphere6.0+struts1.3.. After deploying ,application works fine. After some idle time ,i will get this type of error repeatedly,am not able to login at all. Im not using any connection pooling. i feel after idle time its not able to connect to the database again..if i restart the server everything works fine for some time...after that same story.. please help me out

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  • Switching Between Cards in a CardLayout using getParent()

    - by plutoisaplanet
    Hey everyone, I am writing an application where I am using the CardLayout to swap between two panels that are placed right on top of one another. There's a JPanel called Top, and it's layout is the CardLayout. Inside this JPanel is a JPanel called CMatch. Whenever the user clicks the submit button in the CMatch panel, I want a new JPanel added to Top that is custom built based on what the user types in, and it will be shown instead of the original CMatch panel. All of this done using the CardLayout. These are all different classes in different files, however (the panel Top with CardLayout, the panel CMatch that is inside the Top panel, and the custom built panel). So i tried using the following to add the new panel to the Top panel and then have it shown: (this code takes place in the CMatch class): private void submitButtionActionPerformed(ActionEvent e) { CardLayout cl = (CardLayout)(this.getParent().getLayout()); cl.addLayoutComponent(new CChoice(), "college_choices"); cl.show(this.getParent(), "college_choices"); } However, this didn't work. So i was wondering, what am I doing wrong? Any advice is greatly appreciated, thanks!

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