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  • What is Chain Matrix Multiplication ?

    - by Hellnar
    Hello, I am trying to understand what is a chain matrix multiplication and how it is different from a regular multiplication. I have checked several sourcers yet all seem to be very academically explained for me to understand. I guess it is a form of dynamic programming algorithm to achieve the operation in an optimised way but I didn't go any further. Thanks

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  • Exception durin processing XSLT transformation!

    - by Artic
    I'm usin such code to generate contents file. try { StreamResult result = new StreamResult(); TransformerFactory tf = TransformerFactory.newInstance(); for (String item: groups){ item = item.replaceAll(" ", "-").toLowerCase(); result.setOutputStream(new FileOutputStream(path+item+".html")); Templates templ = tf.newTemplates(xsltSource); Transformer transf = templ.newTransformer(); transf.clearParameters(); transf.setParameter("group", item); transf.transform(xmlSource, result); } } catch (TransformerConfigurationException e) { throw new SinkException(e.getMessage()); } catch (TransformerException e) { throw new SinkException(e.getMessage()); } But on second iteration I have an exception ERROR: javax.xml.transform.TransformerException: com.sun.org.apache.xml.internal.utils.WrappedRuntimeException: Read error Cann't understand what is the reason?

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  • In JSF, how to handle repeating over a list that mutates

    - by Jon
    Hello, In a JSF page, I am iterating over a list of items provided by a session-scoped backing bean. The list needs to be kept up-to-date, so it is replaced with a fresh list every X minutes by a thread (in a thread-safe way). On my page, for each item I provide some text inputs and an "Update" button. If the list is refreshed before I hit "Update", the update does not happen (which is my problem). I happen to be using a4j:repeat, but I think this could also apply to other methods of iteration, including using dataTables. Any thoughts on how I can do this in a non-hackish way? Thanks!

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  • abstract class need acces to subclass atribute

    - by user1742980
    I have a problem with my code. public abstract class SimplePolygon implements Polygon { ... public String toString(){ String str = "Polygon: vertices ="; for(int i = 0;i<varray.length;i++){ str += " "; str += varray[i]; } return str; } } public class ArrayPolygon extends SimplePolygon { private Vertex2D[] varray; public ArrayPolygon(Vertex2D[] array){ varray = new Vertex2D[array.length]; if (array == null){} for(int i = 0;i<array.length;i++){ if (array[i] == null){} varray[i] = array[i]; } ... } Problem is, that i'm not allowed to add any atribute or method to abstract class SimplePolygon, so i'cant properly initialize varray. It could simply be solved with protected atrib in that class, but for some (stupid) reason i'cant do that. Has anybody an idea how to solve it without that? Thanks for all help.

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  • http_access.log on WebSphere 6.1.0.29

    - by DavidG
    I am running WebSphere 6.1.0.29 and I need to track the requests being made to an Enterprise Application. Previously I did this by routing the requests through a proxy server, but I need to repeat the exercise and I figure there must be a simpler way. Does anyone know how to enable HTTP access logging? I have been through the console an thought I had enabled http_access.log and http_error.log via: Application servers server1 HTTP error and NCSA access logging (where 'server1' is the application server) I've enabled the service at startup, and ticked the boxes to enable access logging and error logging - however... nothing has happened. I have restarted the server, restarted the Enterprise apps and even did a "find . -name" for the log files - but they don't seem to be anywhere on the system. I saw on a JavaRanch thread someone suggested writing a custom filter for requests in an application, but this seems like wild overkill - plus I am doing the logs to test a pre-built binary, so I don't want to mess with the code. Anyone have any ideas/suggestions? Help! :-)

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  • How to retrieve the ordered list of best articles having a minimum number of votes by using HSQL ?

    - by fabien7474
    I have a Vote domain class from my grails application containing properties like article_id and note I want to HQL query the Vote domain class in order to retrieve the 5 best rated articles having at least 10 votes. I tried : SELECT v.article_id, avg(v.note), count(*) FROM vote v where count(*) >= 10 group by v.article_id order by avg(v.note) desc limit 5; But unfortunately the insertion of where count(*) >= 10 throws an error. How can I do that in a simple way? Thank you for your help.

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  • How to solve following issues?

    - by lakshmi
    hi im using postgresql database, I want to insert my datas into database,but whenever i run the server,it was display the following Error. Error:org.postgresql.util.PSQLException: FATAL: sorry, too many clients already How to solve this problem.My server.properties file is following. Sever.properties File: serverPortData=9042 serverPortCommand=9078 simocoConnectionURL=jdbc:postgresql://127.0.0.1:5432/vTrack?user=postgres&password=postgres dst=1 DatabaseName=vTrack ServerName=127.0.0.1 User=postgres Password=admin MaxConnections=90 InitialConnections=80 PoolSize=100 MaxPoolSize=100 KeepAliveTime=100 SimocoPoolSize=120 SimocoMaxPoolSize=120 SimocoKeepAliveTime=100 PortNumber=5432 Logging=1 Thanks.

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  • Type mismatch: cannot convert from ArrayList<Data> to MyCollection

    - by Tommy
    I've read similar questions here but I'm still a little confused. MyCollection extends ArrayList<MyClass> MyClass implements Data yet this gives me the "cannot convert from ArrayList to MyCollection" MyCollection mycollection = somehandler.getCollection(); where getCollection looks like this public ArrayList<Data> getCollection() So my assumptions are obviously wrong. How can I make this work like I would like it to

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • Which use cases make temporary JMS queues a better choice than persistent queues?

    - by Stephen Harmon
    When you are designing a JMS application, which use cases make you pick temporary queues over persistent queues? We use temporary queues for response messages. We're having some issues maintaining connections to the temp queues, though, so I am testing persistent response queues, instead. One clear disadvantage of persistent queues is that your application has to "know" about them beforehand. If that's not a big deal, though, are there use cases where temp queues are the obvious choice?

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  • Performance implications of finalizers on JVM

    - by Alexey Romanov
    According to this post, in .Net, Finalizers are actually even worse than that. Besides that they run late (which is indeed a serious problem for many kinds of resources), they are also less powerful because they can only perform a subset of the operations allowed in a destructor (e.g., a finalizer cannot reliably use other objects, whereas a destructor can), and even when writing in that subset finalizers are extremely difficult to write correctly. And collecting finalizable objects is expensive: Each finalizable object, and the potentially huge graph of objects reachable from it, is promoted to the next GC generation, which makes it more expensive to collect by some large multiple. Does this also apply to JVMs in general and to HotSpot in particular?

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  • Is it possible to include JButton in a JTable?

    - by Benjamin Confino
    I have a JTable that stores the results of a database query, so far so good. What I want is for the last column in each table to have a clickible JButton that will open the edit screen for the object represented in that row, and that means the button will need to know the details of the first column in the table from its own row (the ID from the database). Any advice? I already tried just adding JButtons but they turned into Text when I tried to run it.

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  • How do I make my custom Swing component visible?

    - by Alex
    I have no idea why it won't show. First I create an instance of the component and then add it to a certain element in a two-dimensional JPanel array. Then I loop through that array and add each JPanel to another JPanel container which is to hold all the JPanels. I then add that final container to my JFrame window and set visibility to true, it should be visible? public class View extends JFrame { Board gameBoard; JFrame gameWindow = new JFrame("Chess"); JPanel gamePanel = new JPanel(); JPanel[][] squarePanel = new JPanel[8][8]; JMenuBar gameMenu = new JMenuBar(); JButton restartGame = new JButton("Restart"); JButton pauseGame = new JButton("Pause"); JButton log = new JButton("Log"); View(Board board){ gameWindow.setDefaultCloseOperation(EXIT_ON_CLOSE); gameWindow.setSize(400, 420); gameWindow.getContentPane().add(gamePanel, BorderLayout.CENTER); gameWindow.getContentPane().add(gameMenu, BorderLayout.NORTH); gameMenu.add(restartGame); gameMenu.add(pauseGame); gameMenu.add(log); gameBoard = board; drawBoard(gameBoard); gameWindow.setResizable(false); gameWindow.setVisible(true); } public void drawBoard(Board board){ for(int row = 0; row < 8; row++){ for(int col = 0; col < 8; col++){ Box box = new Box(board.getSquare(col, row).getColour(), col, row); squarePanel[col][row] = new JPanel(); squarePanel[col][row].add(box); } } for(JPanel[] col : squarePanel){ for(JPanel square : col){ gamePanel.add(square); } } } } @SuppressWarnings("serial") class Box extends JComponent{ Color boxColour; int col, row; public Box(Color boxColour, int col, int row){ this.boxColour = boxColour; this.col = col; this.row = row; repaint(); } protected void paintComponent(Graphics drawBox){ drawBox.setColor(boxColour); drawBox.drawRect(50*col, 50*row, 50, 50); drawBox.fillRect(50*col, 50*row, 50, 50); } } A final question as well. Notice how each Box component has a position, what happens to the position when I add the component to a JPanel and add the JPanel to my JFrame? Does it still have the same position in relation to the other Box components?

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  • Use ObjectOutputStream and FileOutputStream with FileWriter

    - by wishi
    Hi! Is there any way to use ObjectOutputStream like this: <tag>output of the ObjectOutputStream</tag> If I try: FileOutputStream fos = new FileOutputStream(filename); ObjectOutputStream oos = new ObjectOutputStream(fos); FileWriter fw = new FileWriter(fos); And for example: fw.write("<tag>"); oos.write(cool_object); fw.wrote("</tag>"); I don't get that result. It seems the ObjectOutputStream overwrites the file completly each and every time.

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  • Grails query not using GORM

    - by Tihom
    What is the best way to query for something without using GORM in grails? I have query that doesn't seem to fit in the GORM model, the query has a subquery and a computed field. I posted on stackoverflow already with no response so I decided to take a different approach. I want to query for something not using GORM within a grails application. Is there an easy way to get the connection and go through the result set?

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  • Is it possible to have Ant print out the classpath for a particular target? If so, how?

    - by Daryl Spitzer
    I'm trying to get a target to build that has quite a long list of <pathelement location="${xxx}"/> and <path refid="foo.class.path"/> elements in its <path id="bar.class.path"> element (in the build.xml file). I keep getting "package com.somecompany.somepackage does not exist" errors, and I'm having a hard time chasing down these packages and making sure I've synced them from our repository. I'm new to this team so I'm unfamiliar with the build, but I would prefer to figure this out myself if possible (so I don't bother the other very busy team members). I have very limited experience with Ant. I think it would save me quite a bit of time if I could have Ant print out the classpath for the target I'm trying to build.

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  • ExecutorSerrvice memory leak on exception

    - by TofuBeer
    I am having a hard time tracking this down since the profiler keeps crashing (hotspot error). Before I go too deep into figuring it out I'd like to know if I really have a problem or not :-) I have a few thread pools created via: Executors.newFixedThreadPool(10); The threads connect to different web sites and, on occasion, I get connection refused and wind up throwing an exception. When I later on call Future.get() to get the result it will then catch the ExecutionException that wraps the exception that was thrown when the connection could not be made. The program uses a fairly constant amount of memory up until the point in time that the exceptions get thrown (they tend to happen in batches when a particular site is overloaded). After that point the memory again remains constant but at a higher level. So my question is along the lines of is the memory behaviour (reported by "top" on Unix) expected because the exceptions just triggered something or do I probably have an actual leak that I'll need to track down? Additionally when Future.get() throws an exception is there anything else I need to do besides catch the exception (such as call Future.cancel() on it)?

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  • which toString() method can be used performance wise??

    - by Mrityunjay
    hi, I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :- public String toString() { return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name; } public String toString() { StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return buff.toString(); } public String toString() { StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return builder .toString(); } can anyone please help me to find out which one is best and should be used for enhancing performance.

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