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  • Using inheritance and polymorphism to solve a common game problem

    - by Barry Brown
    I have two classes; let's call them Ogre and Wizard. (All fields are public to make the example easier to type in.) public class Ogre { int weight; int height; int axeLength; } public class Wizard { int age; int IQ; int height; } In each class I can create a method called, say, battle() that will determine who will win if an Ogre meets and Ogre or a Wizard meets a Wizard. Here's an example. If an Ogre meets an Ogre, the heavier one wins. But if the weight is the same, the one with the longer axe wins. public Ogre battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else if (this.axeLength > o.axeLength) return this; else if (this.axeLength < o.axeLength) return o; else return this; // default case } We can make a similar method for Wizards. But what if a Wizard meets an Ogre? We could of course make a method for that, comparing, say, just the heights. public Wizard battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else return this; } And we'd make a similar one for Ogres that meet Wizard. But things get out of hand if we have to add more character types to the program. This is where I get stuck. One obvious solution is to create a Character class with the common traits. Ogre and Wizard inherit from the Character and extend it to include the other traits that define each one. public class Character { int height; public Character battle(Character c) { if (this.height > c.height) return this; else if (this.height < c.height) return c; else return this; } } Is there a better way to organize the classes? I've looked at the strategy pattern and the mediator pattern, but I'm not sure how either of them (if any) could help here. My goal is to reach some kind of common battle method, so that if an Ogre meets an Ogre it uses the Ogre-vs-Ogre battle, but if an Ogre meets a Wizard, it uses a more generic one. Further, what if the characters that meet share no common traits? How can we decide who wins a battle?

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  • hibernate c3p0 broken pipe

    - by raven_arkadon
    Hi, I'm using hibernate 3 with c3p0 for a program which constantly extracts data from some source and writes it to a database. Now the problem is, that the database might become unavailable for some reasons (in the simplest case: i simply shut it down). If anything is about to be written to the database there should not be any exception - the query should wait for all eternity until the database becomes available again. If I'm not mistaken this is one of the things the connection pool could do for me: if there is a problem with the db, just retry to connect - in the worst case for infinity. But instead i get a broken pipe exception, sometimes followed by connection refused and then the exception is passed to my own code, which shouldn't happen. Even if I catch the exception, how could i cleanly reinitialize hibernate again? (So far without c3p0 i simply built the session factory again, but i wouldn't be surprised if that could leak connections (or is it ok to do so?)). The database is Virtuoso open source edition. My hibernate.xml.cfg c3p0 config: <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <property name="hibernate.c3p0.breakAfterAcquireFailure">false</property> <property name="hibernate.c3p0.acquireRetryAttempts">-1</property> <property name="hibernate.c3p0.acquireRetryDelay">30000</property> <property name="hibernate.c3p0.automaticTestTable">my_test_table</property> <property name="hibernate.c3p0.initialPoolSize">3</property> <property name="hibernate.c3p0.minPoolSize">3</property> <property name="hibernate.c3p0.maxPoolSize">10</property> btw: The test table is created and i get tons of debug output- so it seems it actually reads the config.

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  • JUnit: checking if a void method gets called

    - by nkr1pt
    I have a very simple filewatcher class which checks every 2 seconds if a file has changed and if so, the onChange method (void) is called. Is there an easy way to check ik the onChange method is getting called in a unit test? code: public class PropertyFileWatcher extends TimerTask { private long timeStamp; private File file; public PropertyFileWatcher(File file) { this.file = file; this.timeStamp = file.lastModified(); } public final void run() { long timeStamp = file.lastModified(); if (this.timeStamp != timeStamp) { this.timeStamp = timeStamp; onChange(file); } } protected void onChange(File file) { System.out.println("Property file has changed"); } } @Test public void testPropertyFileWatcher() throws Exception { File file = new File("testfile"); file.createNewFile(); PropertyFileWatcher propertyFileWatcher = new PropertyFileWatcher(file); Timer timer = new Timer(); timer.schedule(propertyFileWatcher, 2000); FileWriter fw = new FileWriter(file); fw.write("blah"); fw.close(); Thread.sleep(8000); // check if propertyFileWatcher.onChange was called file.delete(); }

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  • I Want to get a week value

    - by satya
    I wan to get the value of only one week. I am using the following JPA query: SELECT a FROM questions.dao.hibernate.Questions a WHERE (a.posted_date-CURRENT_DATE)>= 7 But I am getting an error message like org.hibernate.QueryException: could not resolve property: posted_date of: questions.dao.hibernate.Questions [SELECT a FROM questions.dao.hibernate.Questions a WHERE (a.posted_date-CURRENT_DATE)>=7] Please help me. Thanks

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  • Redirecting to a Facelet is not working when extending FaceletViewHandler

    - by Abel Morelos
    I'm overriding the handleRenderResponse method defined in com.sun.facelets.FaceletViewHandler: protected void handleRenderException(FacesContext context, Exception ex) I'm overriding this method so I can redirect the user to a custom error page (which contain the desired look and feel and other stuff). This is the way I'm trying to String errorPage = "/error.xhtml"; String contextPath = context.getExternalContext().getRequestContextPath(); String errorPagePath = contextPath+errorPage; context.getExternalContext().redirect(errorPagePath); The previous code is what I'm using to perform the redirect to this custom error page. Anyway, when I perform the redirect I'm prompted with a download dialog (this is with Internet Explorer, in Firefox the page does not display properly or as I would expect). I tried changing "/error.xhtml" to "/error.jsf" but in that case I get a 404 error. Somehow I think that the XHTML file is not being handled to the Facelets ViewHandler after the redirect, if I open the downloaded xhtml file I can see that the EL expressions were not resolved and the the ui tags were not handled. I don't have problems with other pages in my application, only when doing the redirect programatically. Important data from my web.xml: facelets.VIEW_MAPPINGS is set to *.xhtml javax.faces.DEFAULT_SUFFIX is set to .xhtml servlet-mapping for the "Faces Servlet" is ".jsf" and "/faces/"

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  • Handle Transaction on differents EARs

    - by rfders
    Hello, what is the best practice to handle multiple EARs and the same transaction, as far as we know we need to apply XA concepts in order transaction works correctly. but apparently in currents project that we've been working on, this is not strictly necessary for creates and updates; however if we try to retrieve any collection from an entity we get an error that say there its not an active transaction or it was closed, but if we update Entity A in Ear A and update Entity B in Ear B it works perfectly when Entity A and Entity B has different datasources, at this point we are so confused about that, because we haven't configure any xa datasource yet. how is the best approach to work with this. transaction are handles by beans and not by the container and datasource are different between EAR A and EAR B

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  • OpenGL extensions available on different Android devices

    - by MH114
    I'm in the process of writing an OpenGL ES powered framework for my next Android game(s). Currently I'm supporting three different techniques of drawing sprites: the basic way: using vertex arrays (slow) using vertex-buffer-objects (VBOs) (faster) using the draw_texture extension (fastest, but only for basic sprites, i.e. no transforming) Vertex arrays are supported in OpenGL ES 1.0 and thus in every Android-device. I'm guessing most (if not all) of the current devices also support VBOs and draw_texture. Instead of guessing, I'd like to know the extensions supported by different devices. If majority of devices support VBOs, I could simplify my code and focus only on VBOs + draw_texture. It'd be helpful to know what different devices support, so if you have an Android-device, do report the extensions list please. :) String extensions = gl.glGetString(GL10.GL_EXTENSIONS); I've got a HTC Hero, so I can share those extensions next.

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  • JSTL param implicit object

    - by srinannapa
    Hi , i'm using struts 2 and jstl. facing problem with param implicit object. Here is the test code : <% request.setAttribute ("error", "Failed"); %> <%= request.getAttribute("error") %> ----------> Prints "Failed" <c:out value="${param.error}"></c:out> ---------> Prints nothing?? Why param.error is not producing the result.

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  • Does calling a click method effect the HtmlPage object if there is a 404?

    - by Blankman
    If I call a click method on a HtmlAnchor, and say that page returns a 404, does that mean the HtmlPage will effect, so searching for another link on the page will result in an error because the page's HTML is the error page (assuming the link is NOT on the error page). Can I manually set the page's HTML, and then locate and click on links and continue on from this approach? (other than connecting via a URL)

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  • Pageview implementation

    - by The Elite Gentleman
    Hi everyone I want to add a pageview feature on my current web application. This page view is based on the count of user viewing the page. It must be unique, i.e. I must not view a person's page 10000 times and record it as 10000 views, just record 1 view instead. My question is, should I base my pageview count on IP address? If not, what is/are the best approach in doing this? I know that if the person has logged in to my system, I can simply use the user id stored in the session and check on the record if the user has/hasn't viewed the page and update accordingly. But for "anonymous" viewers, what is the best approach? Thanks. PS How does Youtube does it?

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  • How do I structure a GWT project?

    - by smaye81
    Hello, I have followed the basic GWT tutorial for creating a project in Eclipse. Now, I am trying to build off what I learned in the tutorial. I created a static utility class to perform some database connection logic. However, when I try to compile I get: [ERROR] Line 46: No source code is available for type com.sample.server.ConnectionUtil; did you forget to inherit a required module? Where can I put simple classes that I've created on my own? Do they have to be outside the package structure of the basic module, 'com.sample'? Or do I have to specify a whole new module in the gwt.xml file and inherit from that? There has to be something simple I'm missing.

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  • Migration solution for singletons in an OSGI environment

    - by Ido
    I'm working in a JEE Environment in which each application is in a war file of its own. In the WEB-INF/lib of each application war file there is a common jar that is shared by all applications. This common jar contains several Singletons which are accessed from many points in the code. Because of the war-file boundaries each application has its own instances of the Singletons. Which is how we operate today, since we want to configure some of the singletons differently in each application. Now we are moving towards an OSGi environment, where this solution will no longer work since each bundle has its own class loader, so if I try to access MySingleton which resides in bundle "common.jar" from bundle "appA.jar" or from bundle "appB.jar" I will get the same instance. Remember I "want" a different instance of a singleton per bundle. (as ironic as it sounds) Now I realize the ideal solution would be to fix the code to not rely on those singletons, however due to a tight schedule I was wondering if you guys can suggest some sort of a migration solution that would allow me to use bundle-wide singletons so each of them could be configured per bundle.

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  • Getting a nicely formatted timestamp without lots of overhead?

    - by Brad Hein
    In my app I have a textView which contains real-time messages from my app, as things happen, messages get printed to this text box. Each message is time-stamped with HH:MM:SS. Up to now, I had also been chasing what seemed to be a memory leak, but as it turns out, it's just my time-stamp formatting method (see below), It apparently produces thousands of objects that later get gc'd. For 1-10 messages per second, I was seeing 500k-2MB of garbage collected every second by the GC while this method was in place. After removing it, no more garbage problem (its back to a nice interval of about 30 seconds, and only a few k of junk typically) So I'm looking for a new, more lightweight method for producing a HH:MM:SS timestamp string :) Old code: /** * Returns a string containing the current time stamp. * @return - a string. */ public static String currentTimeStamp() { String ret = ""; Date d = new Date(); SimpleDateFormat timeStampFormatter = new SimpleDateFormat("hh:mm:ss"); ret = timeStampFormatter.format(d); return ret; }

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  • Can Hibernate default a Null String to Empty String

    - by sliver
    In our application we are pulling data from a DB2 mainframe database. If the database has "low values" in a field, hibernate sends a "null" value in the object. This occurs even if the column is defined as "not null". As we are doing XML parsing on this, Castor is having trouble with it. I would like to fix this in Hibernate. Also, all of the hibernate hbm files are generated, so we can't mess with them (they are regened from time to time.) Any way to intercept all Strings and replace nulls with ""?

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  • Servlet unit test

    - by Thomman
    Currently I'm using TestNG framework for testing application business logic, i added some Servlet classes recently. How do I unit test these Servlet classes in TestNg framework?

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  • taglib with constants functionality?

    - by jack
    I need to use some constants in my JSP. Now I'd like to use this without using scriptlets. (and adding getters is not an option, it's an external jar) Using the search I've seen that some people put them in a map. However I've seen that there's a constants function in the unstandard taglib but that is a few years old and so far I haven't found a maven repository with it. So are there any other taglibs with this functionality?

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  • How can I pipe a large amount of data as a runtime argument?

    - by Zombies
    Running an executable JAR on a linux platform here. The program it self works on a somewhat large amount of data, basically a list of URLs... could be up to 2k. Currently I get this from a simple DB call. But I was thinking that instead of creating a new mode and writing SQL to get a new result set and having to redploy everytime, I could just make the program more robust by passing in the result set (the list of URLs) that need to be worked on... so, within a linux environment, is there a pain-free/simple way to get the result set and pass it in dynamically? I know file i/o is one, but it doesn't seem to be effecient because each file has to be named, as well more logic to handle grabbing the correct file, creating a file with a unique name, etc.

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  • Bulding an multi-platform SWT application using Ant

    - by Mridang Agarwalla
    I'm writing an SWT application which can be used on Windows (32/64 bit) and Mac OSX (32/64 bit). Apart from the JRE I rely on the SWT library found here. I can find four versions of the SWT library depending upon my target platforms (as mentioned above). When building my application, how can I compile using the correct SWT Jar? If possible, I'd like to try and avoid hard-coding the Jar version, platform and architecture. The SWT Jars are named like this: swt-win32-x86_64.jar swt-win32-x86_32.jar swt-macosx-x86_32.jar swt-macosx-x86_64.jar (My project will be an open source project. I'd like people to be able to download the source and build it and therefore I've thought of including all the four versions of the SWT Jars in the source distribution. I hope this is the correct approach of publishing code relying on third-part libraries.) Thanks everyone.

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  • Why won't this println command start a new line?

    - by David
    Here's the relevant code: public static void printBoarders (Territory x) { int t = 0 ; int n = 0 ; for (int i = 0; i<x.borders.length; i++) { if (x.borders[i] == -1) t = i ; } for (int j = 0; j<x.borders.length; j++) { if (x.borders[j] == 1) n++ ; } Territory.translate (t) ; System.out.print (" has " + n + " borders: ") ; Territory.translate (x.borders) ; System.out.println (" ") ; } When I run this, I get everything on one line without a line break. Why isn't the System.out.println (" ") ; creating a line break? Here is an example of what the output winds up being: Northwest Territory, Alberta, Kamchatka, hidavid-names-macbook-pro:~ davidname$ EDIT: the problem was that this method was never being invoked. A different one which i was replacing was. All is well.

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