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  • Limiting one of each Runnable type in ExecutorService queue.

    - by Andrew
    I have an Executors.newFixedThreadPool(1) that I send several different tasks to (all implementing Runnable), and they get queued up and run sequentially correct? What is the best way to only allow one of each task to be either running or queued up at one time? I want to ignore all tasks sent to the ExecutorService that are already in the queue.

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  • Representing game states in Tic Tac Toe

    - by dacman
    The goal of the assignment that I'm currently working on for my Data Structures class is to create a of Quantum Tic Tac Toe with an AI that plays to win. Currently, I'm having a bit of trouble finding the most efficient way to represent states. Overview of current Structure: AbstractGame Has and manages AbstractPlayers (game.nextPlayer() returns next player by int ID) Has and intializes AbstractBoard at the beginning of the game Has a GameTree (Complete if called in initialization, incomplete otherwise) AbstractBoard Has a State, a Dimension, and a Parent Game Is a mediator between Player and State, (Translates States from collections of rows to a Point representation Is a StateConsumer AbstractPlayer Is a State Producer Has a ConcreteEvaluationStrategy to evaluate the current board StateTransveralPool Precomputes possible transversals of "3-states". Stores them in a HashMap, where the Set contains nextStates for a given "3-state" State Contains 3 Sets -- a Set of X-Moves, O-Moves, and the Board Each Integer in the set is a Row. These Integer values can be used to get the next row-state from the StateTransversalPool SO, the principle is Each row can be represented by the binary numbers 000-111, where 0 implies an open space and 1 implies a closed space. So, for an incomplete TTT board: From the Set<Integer> board perspective: X_X R1 might be: 101 OO_ R2 might be: 110 X_X R3 might be: 101, where 1 is an open space, and 0 is a closed space From the Set<Integer> xMoves perspective: X_X R1 might be: 101 OO_ R2 might be: 000 X_X R3 might be: 101, where 1 is an X and 0 is not From the Set<Integer> oMoves perspective: X_X R1 might be: 000 OO_ R2 might be: 110 X_X R3 might be: 000, where 1 is an O and 0 is not Then we see that x{R1,R2,R3} & o{R1,R2,R3} = board{R1,R2,R3} The problem is quickly generating next states for the GameTree. If I have player Max (x) with board{R1,R2,R3}, then getting the next row-states for R1, R2, and R3 is simple.. Set<Integer> R1nextStates = StateTransversalPool.get(R1); The problem is that I have to combine each one of those states with R1 and R2. Is there a better data structure besides Set that I could use? Is there a more efficient approach in general? I've also found Point<-State mediation cumbersome. Is there another approach that I could try there? Thanks! Here is the code for my ConcretePlayer class. It might help explain how players produce new states via moves, using the StateProducer (which might need to become StateFactory or StateBuilder). public class ConcretePlayerGeneric extends AbstractPlayer { @Override public BinaryState makeMove() { // Given a move and the current state, produce a new state Point playerMove = super.strategy.evaluate(this); BinaryState currentState = super.getInGame().getBoard().getState(); return StateProducer.getState(this, playerMove, currentState); } } EDIT: I'm starting with normal TTT and moving to Quantum TTT. Given the framework, it should be as simple as creating several new Concrete classes and tweaking some things.

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  • Detecting when a handler couldn't be started when embedding Jetty

    - by scompt.com
    I'm embedding Jetty in a similar manner as described here. When the RequestLogHandler can't open the specified logfile, it throws an exception which is unfortunately caught by org.eclipse.jetty.server.Server and swallowed (but logged first, at least). This means that there's no obvious way for me to tell if the log handler was started correctly. Is there a way that I'm missing to detect when a handler couldn't start?

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  • getting JSlider bar to move on mouse click event

    - by Aly
    Hi, I have a JSlider which shows bet sizes (for a poker game) I am trying to achieve the effect that when a mouse click occurs the slider jumps forward by a bet amount (i.e. a big blind amount) rather than just incrementing by one. If the mouse click happens to the left of the bar i want it to decrement by a fixed amount else increment. I looked into attaching a mouse listener, but do not know how I can use the event to find out on what side of the bar the mouse was clicked. Any ideas?

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  • Accessing Spring beans from a Tiles view (JSP)

    - by Sinuhe
    In Spring MVC I can access my beans in JSP using JstlView's exposedContextBeanNames (or exposeContextBeansAsAttributes). For example, then, in my JSP I can write (${properties.myProperty). But when the same JSP is a part of a tiles view, these properties aren't accessible. Is possible to configure Tiles properly or access these properties in another way? I'm using Spring MVC 3.0.2 and Tiles 2.2.1. Here's a bit of my configuration: <bean id="tilesViewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver"> <property name="order" value="1"/> <property name="viewClass" value="org.springframework.web.servlet.view.tiles2.TilesView" /> </bean> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="order" value="2"/> <property name="prefix" value="/WEB-INF/views/"/> <property name="suffix" value=".jsp"/> <property name="exposedContextBeanNames"> <list><value>properties</value></list> </property> </bean>

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  • problem with unicode in javaEE and save question mark in database

    - by Jeus
    when i insert persian information with use JEE6(JSF and JPA) my information save question mark for example "???" === "???" my database is Mysql and my table is UTF-8 . when insert persian data directly in database is correct and save correct. i know that with change one property in JEE my problem go to solved but i don`t know where is it ?

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  • Jasper exported to Excel ignoring background color?

    - by discgolfer
    Have you ever had alternating background colors in a Jasper report and then exported it to Excel? The Excel export seems to ignore the alternating color. I've got a Jasper report where the rows alternating background color using the procedure referenced HERE. When I preview it using the viewer or export to PDF it works -- but not when I export to Excel. I've tried using JRXlsExporter and JExcelApiExporter both to no avail. I think it might be a side-effect of how you have to make alternating row colors in Jasper, which I despise to begin with, but have found no other way. Thanks in advance!

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  • Cannot capture TouchEvent.UP in Blackberry

    - by Nandu
    I am working on a Scrollable Image field.I am handling TouchEvent.DOWN mTouchEvent.MOVE,TouchEvent.UP. Somehow control never goes to TouchEvent.UP section.How to capture the UP event. I have to findout the start and end points of the drag. My Code looks like this.. if (event == TouchEvent.DOWN && touchEvent.isValid()) { _xTouch = touchEvent.getX(1); _yTouch = touchEvent.getY(1); } else if(event == TouchEvent.UP && touchEvent.isValid()) { int x = touchEvent.getX(1); int y = touchEvent.getY(1); } else if (event == TouchEvent.MOVE && touchEvent.isValid()) { boolean result = scrollImage((touchEvent.getX(1) - _xTouch), (touchEvent.getY(1) - _yTouch)); _xTouch = touchEvent.getX(1); _yTouch = touchEvent.getY(1); //If scrolling occurred, consume the touch event. if (result) { return true; } else { return false; } } Thanks in advance.

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  • Get children count via HQL

    - by Thomas Lötzer
    Hi, I have a one-to-many mapping between a parent entity and child entities. Now I need to find the number of children associated with each parent for a list of parents. I am trying to do this with HQL but I am not sure how I can get the list of parents in there. Also, I don't know how I can return the entity itself and not just its ID. My current HQL query is: select new map(parent.id as parentId, count(*) as childCount) from Parent parent left join parent.children children group by parent.id but this only returns the ID and does not filter on specific parents. EDIT Based on Pascal's answer I have modified the query to select new map(parent as parent, count(elements(parent.children)) as childCount) from Parent parent group by parent That does work, but is prohibitively slow: 30 seconds instead of 400 ms on the same database.

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  • Computing unique index for every poker starting hand

    - by Aly
    As there are 52 cards in a deck we know there are 52 choose 2 = 1326 distinct matchups, however in preflop poker this can be bucketed into 169 different hands such as AK offsuit and AK suited as whether it is A hearts K hearts or A spade K spades it makes no difference preflop. My question is, is there a nice mathematical property in which I can uniquely index each of these 169 hands (from 0 to 168 preferably). I am trying to create a look up table as a double[][] = new double [169][169] but have no way of changing a hand representation such as AKs (an Ace and a King of the same suit) to a unique index in this array.

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  • How to avoid using this in a constructor

    - by Paralife
    I have this situation: interface MessageListener { void onMessageReceipt(Message message); } class MessageReceiver { MessageListener listener; public MessageReceiver(MessageListener listener, other arguments...) { this.listener = listener; } loop() { Message message = nextMessage(); listener.onMessageReceipt(message); } } and I want to avoid the following pattern: (Using the this in the Client constructor) class Client implements MessageListener { MessageReceiver receiver; MessageSender sender; public Client(...) { receiver = new MessageReceiver(this, other arguments...); sender = new Sender(...); } . . . @Override public void onMessageReceipt(Message message) { if(Message.isGood()) sender.send("Congrtulations"); else sender.send("Boooooooo"); } } The reason why i need the above functionality is because i want to call the sender inside the onMessageReceipt() function, for example to send a reply. But I dont want to pass the sender into a listener, so the only way I can think of is containing the sender in a class that implements the listener, hence the above resulting Client implementation. Is there a way to achive this without the use of 'this' in the constructor? It feels bizare and i dont like it, since i am passing myself to an object(MessageReceiver) before I am fully constructed. On the other hand, the MessageReceiver is not passed from outside, it is constructed inside, but does this 'purifies' the bizarre pattern? I am seeking for an alternative or an assurance of some kind that this is safe, or situations on which it might backfire on me.

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  • why wont this tester complie

    - by user1678800
    student name and id and testgrade need to compile with tester but the student class has some problem i dont know what it is and the error message is Error: Syntax error on token "(", . expected this needs to complie with the tester class to be able to run public class Student { public static void main(String[] args) { // instant varible for name, id , and test grade private String name; private int id; private int testgrade; /** * construct class * @parm String newName * @parm String newId */ public Student(String newName, int newId); { name = newName; id = newId; } /** * getName method that return instant varible name */ public String getName() { return name; } /** * getId method that return instant varible id */ public int getId() { return id; } /** * setGrade method that sets the test grade variable * * @param int grade */ public void setGrade(int grade) { testGrade = grade; } /** * getGrade method that sets test grade instance variable * * @param int grade */ public int getGrade() { return testGrade; } } }

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  • How to prevent "Local transaction already has 1 non-XA Resource" exception?

    - by Zeratul
    Hi, I'm using 2 PU in stateless EJB and each of them is invoked on one method: @PersistenceContext(unitName="PU") private EntityManager em; @PersistenceContext(unitName="PU2") private EntityManager em2; @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) public void getCandidates(final Integer eventId) throws ControllerException { ElectionEvent electionEvent = em.find(ElectionEvent.class, eventId); ... Person person = getPerson(candidate.getLogin()); ... } @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW ) private Person getPerson(String login) throws ControllerException { Person person = em2.find(Person.class, login); return person; } Those methods are annotated with REQUIRES_NEW transcaction to avoid this exception. When I was calling these method from javaFX applet, all worked as expected. Now I'm trying to call them from JAX-RS webservice (I don't see any logical difference as in both cases ejb was looked up in initial context) and I keep getting this exception. When I set up XADatasource in glassfish 2.1 connection pools, I got nullpointer exception on em2. Any ideas what to try next? Regards

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  • HyperJAXB and IDREFs

    - by finrod
    I have eventually managed to fiddle HyperJAXB so that when XSD has complexType A and this has an IDREF to complexType B, then HyperJAXB will generate @OneToOne JPA annotations between the the two generated entities. However now I'm facing another problem: the XSD has complex type X that can IDREF to either complex type Y or complex type Z. In the end, I need instance of complex type X contain reference to either instance of class Y or class Z. Do you have any wild ideas how can this be done without manual alterations to the generated classes? And at the same time to make sure these entities are marshalled to a correct XML? How about using the JAXB plugin that allows generating classes so that they implement a particular interface? Could that lead anywhere?

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  • Jersey (Jax-RS) & EL

    - by smeg4brains
    Hi there! im trying to get a controller to return a view through a Expression Language-Filter, but have no idea on how to get jersey to use EL for filtering a view. View with EL-tags: <html> <title>%{msg}</title> </html> Controller: @GET @Produces("text/html") public Response viewEventsAsHtml(){ String view=null; try { view=getViewAsString("events"); }catch(IOException e){ LOG.error("unable to load view from file",e); return null; } Response.ResponseBuilder builder=Response.ok(view, MediaType.TEXT_HTML); return builder.build(); } How would one go about in order to get the controller to replace the ${msg} part in the view by some arbitrary value?

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  • Prevent SQL injection from form-generated SQL.

    - by Markos Fragkakis
    Hi all, I have a search table where user will be able to filter results with a filter of the type: Field [Name], Value [John], Remove Rule Field [Surname], Value [Blake], Remove Rule Field [Has Children], Value [Yes], Remove Rule Add Rule So the user will be able to set an arbitrary set of filters, which will result essentially in a completely dynamic WHERE clause. In the future I will also have to implement more complicated logical expressions, like Where (name=John OR name=Nick) AND (surname=Blake OR surname=Bourne), Of all 10 fields the user may or may not filter by, I don't know how many and which filters the user will set. So, I cannot use a prepared statement (which assumes that at least we know the fields in the WHERE clause). This is why prepared statements are unfortunately out of the question, I have to do it with plain old, generated SQL. What measures can I take to protect the application from SQL Injection (REGEX-wise or any other way)?

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  • What is the best way to handle validity dates in applications ?

    - by user214626
    Hello, How do we model these objects ? Scenario 1: Price changes in a time period EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-02-01 Null 900$ So, if the price changes to 910$ on 2009-02-15, then the system should automatically update the expiry date on the previous effective price to 2009-02-14, to keep it consistent. Scenario 2: No price specified between 2009-02-01 to 2009-02-28 EffectiveDate ExpiryDate Price 2009-01-01 2009-01-31 800$ 2009-03-01 Null 900$ So, if new price is specified for 2009-02-15 onwards , then the system should automatically set the expiry date on the record to be inserted to 2009-02-28, because already a record effective from 2009-03-01 exists. Please suggest an effective way to handle these scenarios to model my framework, or are there any frameworks around that can do this . Thanks

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  • method names with fluent interface

    - by deamon
    I have a Permissions class with methods in fluent style like this: somePermissions.setRead(true).setWrite(false).setExecute(true) The question is, whether I should name these methods set{Property} or only {property}. The latter would look like this: somePermissions.read(true).write(false).execute(true) If I look at these methods separately I would expect that read reads something, but on the other hand it is closer to the intention to have something like named paramaters like in Scala: Permission(read=true, write=false, execute=true)

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  • Vehicle 2 Vehicle Communication Questions

    - by pinnacler
    I have a rare opportunity to meet the man in charge of implementing vehicle 2 vehicle communication for the US Department of Transportation with 2 others in a few hours. Do YOU have any questions for him? I know this is a little outside the normal, but this is a 'reverse' thread and I felt he has some great knowledge on the subject that I want to share with this community. I'll post his answers later today to his questions. Ask about V2V implementation, privacy issues, use cases, or if you've thought of a great way to use V2V and want me to share it with him, he can at least think about it. He is in charge of panel that creates the standard. Or anything else...

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  • Android Hashtable Serialization

    - by Nsyed
    Hi All, I am having a weird issue with serialization of a Hashtable. I have made a Server, Client app. Where server(PC/MAC) is serializing a Hashtable and sending it to Client(Android) through UDP. The data is sent/read correctly but I get a bunch of these messages below on LogCat. 04-12 11:19:43.059: DEBUG/dalvikvm(407): GetFieldID: unable to find field Ljava/util/Hashtable;.loadFactor:F Occasionally, I would see these 04-12 11:21:19.150: DEBUG/dalvikvm(407): GC freed 10814 objects / 447184 bytes in 97ms The app would run for 2-3 mins and then crash. Interestingly enough I do not see the Loadfactor errors on SDK 1.5. But I do see the GC Free xxxx objects, quiet often. After debugging I have found that the issue is with de-serialization and the error/warning are coming from following code Code: ByteArrayInputStream bis = new ByteArrayInputStream(bytes); ObjectInputStream ois = new ObjectInputStream(bis); object = ois.readObject(); at Code: object = ois.readObject(); on the client. My server is serializing code is the following. Code: ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(obj); Any idea what is going on? Thanks for the Help!

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