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  • Creating a shared HSQLDB database

    - by Robert Munteanu
    In-process HSQLDB database are not expected to be opened by others, even for file-based storage. The documentation hints that this is possible: Server Modes, Advanced Topics, but I've not yet found a URL for how to activate this behaviour. Did anyone do this so they can share how to?

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  • How to prevent the other threads from accessing a method when one thread is accessing a method?

    - by geeta
    I want to search for a string in 10 files and write the matching lines to a single file. I wrote the matching lines from each file to 10 output files(o/p file1,o/p file2...) and then copied those to a single file using 10 threads. But the output single file has mixed output(one line from o/p file1,another line from o/p file 2 etc...) because its accessed simultaneously by many threads. If I wait for all threads to complete and then write the single file it will be much slower. I want the output file to be written by one thread at a time. What should i do? My source code:(only writing to single file method) public void WriteSingle(File output_file,File final_output) throws IOException { synchronized(output_file){ System.out.println("Writing Single file"); FileOutputStream fo = new FileOutputStream(final_output,true); FileChannel fi = fo.getChannel(); FileInputStream fs = new FileInputStream(output_file); FileChannel fc = fs.getChannel(); int maxCount = (64 * 1024 * 1024) - (32 * 1024); long size = fc.size(); long position = 0; while (position < size) { position += fc.transferTo(position, maxCount, fi); } } }

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  • How to implement a ilike Facebook system without user authentication and still prevent users from cheating ?

    - by fabien7474
    Hi, I am trying to implement something done in almost any website out there : a 'ilike' button (like Facebook) that does not require user authetication to be used for any article of my website written in Grails. I don't want to use any external solution, so I need to implement it myself (or use a grails plugin). So my question is : What does it take to implement this 'ilike' button and prevent users from cheating? For instance, do I need to store local cookies (I suppose yes)? Do I need to check the session ID and IP of the HTTP request? Any well-known implementation are welcomed. Thank you very much for your help.

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  • Programatically Add a AnnotationSessionFactoryBean

    - by user146714
    Hi, I have a class that implements BeanDefinitionRegistryPostProcessor. I am trying to add an AnnotationSessionFactoryBean to my Spring Context in either postProcessBeanFactory or postProcessBeanDefinitionRegistry. I need to do this programatically so that I can configure the object at runtime. I am trying to do: @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry bdr) throws BeansException { RootBeanDefinition bd = new RootBeanDefinition( AnnotationSessionFactoryBean.class); // fails here.. can not cast AnnotationSessionFactoryBean asfb = (AnnotationSessionFactoryBean)bd; bdr.registerBeanDefinition("sessionFactory", asfb); thanks for your help --updated with solution: had to do a: GenericBeanDefinition bd = new GenericBeanDefinition(); bd.setBeanClass(AnnotationSessionFactoryBean.class); bd.getPropertyValues().add("dataSource", dataSource); bdr.registerBeanDefinition("sessionFactory", bd);

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  • When should EntityManagerFactory instance be created/opened ?

    - by masato-san
    Ok, I read bunch of articles/examples how to write Entity Manager Factory in singleton. One of them easiest for me to understand a bit: http://javanotepad.blogspot.com/2007/05/jpa-entitymanagerfactory-in-web.html I learned that EntityManagerFactory (EMF) should only be created once preferably in application scope. And also make sure to close the EMF once it's used (?) So I wrote EMF helper class for business methods to use: public class EmProvider { private static final String DB_PU = "KogaAlphaPU"; public static final boolean DEBUG = true; private static final EmProvider singleton = new EmProvider(); private EntityManagerFactory emf; private EmProvider() {} public static EmProvider getInstance() { return singleton; } public EntityManagerFactory getEntityManagerFactory() { if(emf == null) { emf = Persistence.createEntityManagerFactory(DB_PU); } if(DEBUG) { System.out.println("factory created on: " + new Date()); } return emf; } public void closeEmf() { if(emf.isOpen() || emf != null) { emf.close(); } emf = null; if(DEBUG) { System.out.println("EMF closed at: " + new Date()); } } }//end class And my method using EmProvider: public String foo() { EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getInstance().getEntityManagerFactory().createEntityManager(); Query query = em.createNativeQuery(JPQL_JOIN); //just some random query out = query.getResultList(); } catch(Exception e) { //handle error.... } finally { if(em != null) { em.close(); //make sure to close EntityManager } } I made sure to close EntityManager (em) within method level as suggested. But when should EntityManagerFactory be closed then? And why EMF has to be singleton so bad??? I read about concurrency issues but as I am not experienced multi-thread-grammer, I can't really be clear on this idea.

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  • How do "modern JVMs" differ from older JVMs?

    - by Lord Torgamus
    Here's a phrase that I heard a lot throughout high school and university computer science classes: "That's not an issue for modern JVMs." Usually this would come up in discussions about overall performance or optimization strategies. It was always treated as a kind of magical final answer, though, as if it makes issues no longer worth thinking about. And that just leads me to wonder: what are the differences between the prototypical "modern JVM" and older JVMs, really?

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  • Getting a JFrame's actual current location

    - by Ian Fellows
    Hello community, I am trying to create a (child) JFrame which slides out from underneath one side of a second (parent) JFrame. The goal is to then have the child follow the parent around when it is moved, and respond to resizing events. This is somewhat related to this question. I have tried using a ComponentListener, but with this method the child only moves once the parent has come to a stop, whereas I would like the child to move as the parent is dragged around the screen. Another option I attempted was to start a new refresher thread that continually updated the child's location using getLocation() or getLocationOnScreen(), but the lag was the same as with ComponentListener. Is there a way to get the true actual location of a JFrame even in the midst of a drag? or if not, is there a way to get the effect of a sheet sliding out from underneath and following the Frame around?

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  • JMS - How do message selectors work with multiple queue and topic consumers?

    - by Stephen Harmon
    Say you have a JMS queue, and multiple consumers are watching the queue for messages. You want one of the consumers to get all of a particular type of message, so you decide to employ message selectors. For example, you define a property to go in your JMS message header named, "targetConsumer." Your message selector, which you apply to the consumer known as, "A," is something like "WHERE targetConsumer = "CONSUMER_A." It's clear that consumer A will now just grab messages with the property set like it is in in the example. Will the other consumers have awareness of that, though? IOW, will another consumer, unconstrained by a message selector, grab the "CONSUMER_A" messages, if it looks at the queue before Consumer A? Do I need to apply message selectors like, "WHERE targetConsumer < "CONSUMER_A" to the others? I am RTFMing and gathering empirical data now, but was hoping someone might know off the top of their head.

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  • Reusing of a PreparedStatement between methods?

    - by MRalwasser
    We all know that we should rather reuse a JDBC PreparedStatement than creating a new instance within a loop. But how to deal with PreparedStatement reuse between different method invocations? Does the reuse-"rule" still count? Should I really consider using a field for the PreparedStatement or should I close and re-create the prepared statement in every invocation? (Of course an instance of such a class would be bound to a Connection which might be a disadvantage) I am aware that the ideal answer might be "it depends". But I am looking for a best practice for less experienced developers that they will do the right choice in most of the cases.

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  • How do I create a new AnyType[] array?

    - by cb
    Which is the best practice in this situation? I would like an un-initialized array of the same type and length as the original. public static <AnyType extends Comparable<? super AnyType>> void someFunction(AnyType[] someArray) { AnyType[] anotherArray = (AnyType[]) new Comparable[someArray.length]; ...or... AnyType[] anotherArray = (AnyType[]) new Object[someArray.length]; ...some other code... } Thanks, CB

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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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  • Is there a faster method then StringBuilder for a max 9-10 step string concatenation?

    - by Pentium10
    I have this code to concate some array elements: StringBuilder sb = new StringBuilder(); private RatedMessage joinMessage(int step, boolean isresult) { sb.delete(0, sb.length()); for (int i = 0; i <= step; i++) { if (mStack[i] == null) continue; rm = mStack[i].getCurrentMsg(); if (rm == null || rm.msg.length() == 0) continue; if (sb.length() != 0) { sb.append(", "); } sb.append(rm.msg); } return sb.toString(); } Important the array holds max 10 items, so it's not quite much. My trace output tells me this method is called 18864 times, 16% of the runtime was spent in this method. Can I optimize more?

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  • How can I change the arrow style in a JComboBox

    - by Stephane Grenier
    Let's say I want to use a custom image for the arrow in JComboBox, how can I do this? I understand it's possible using the synth xml files, or maybe even UIManager.put(...), but I don't know how. All I want to do at this time is change the arrow image to something else, either programatically or even just overriding the image it uses. How exactly can I do this?

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  • Collections removeAll method

    - by srinannapa
    I would like to know if something like below is possible , list<**MyObject**>.**removeAll**(list<**String**>) I hope the context is understandable. The list<MyObject : is a ArrayList<MyObject The list<String : is a ArrayList<String I know this can be achieved by overriding equals method in MyObject class. I would like to know if any other choice is prsent. Thanks,Srinivas N

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  • How to re-order a List<String>

    - by tarka
    I have created the following method: public List<String> listAll() { List worldCountriesByLocal = new ArrayList(); for (Locale locale : Locale.getAvailableLocales()) { final String isoCountry = locale.getDisplayCountry(); if (isoCountry.length() > 0) { worldCountriesByLocal.add(isoCountry); Collections.sort(worldCountriesByLocal); } } return worldCountriesByLocal; } Its pretty simple and it returns a list of world countries in the users locale. I then sort it to get it alphabetic. This all works perfectly (except I seem to occasionally get duplicates of countries!). Anyway, what I need is to place the US, and UK at the top of the list regardless. The problem I have is that I can't isolate the index or the string that will be returned for the US and UK because that is specific to the locale! Any ideas would be really appreciated.

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  • How to add netbeans platform for compiling iReport sources?

    - by user356108
    I need to customize iReport sources.. (not creating plugin) Currently i am using iReport 3.7.2 and netbeans 6.5.1 ide. I downloaded the netbeans platform 6.0.1 and followed the procedures as shown in the jaspersoft link on how to compile iReport sources. But when i tried to compile the sources. I am getting errors like libs-xerces-jar is of incompatible specification version. And if i replace the jar new version of that jar in the NetBeans platform 6.0.1-200801291616 folder I am getting org-netbeans-awt.jar is of incompatiable specification version. and the same incompatiable specification version error is throwing for other jars in the netbeans platform folder. Can anyone help me in this issue

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  • Any big difference between using contains or loop through a list?

    - by Nazgulled
    Hi, Performance wise, is there really a big difference between using: ArrayList.contains(o) vs foreach|iterator LinkedList.contains(o) vs foreach|iterator HashMap.(containsKey|containsValue) vs foreach|iterator TreeMap.(containsKey|containsValue) vs foreach|iterator Of course, for the foreach|iterator loops, I'll have to explicitly compare the methods and return true or false accordingly. The object I'm comparing is an object where equals() and hashcode() are both properly overridden.

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  • How to put PrintWriter object content in to table cell

    - by user3599482
    I have a small problem about a content returning from servlet to put in table cell. In javascript I am calling servlet method using post, it returns some content and I have to put it in two different <td> cells. here is my code, In javascript, $.post('<%=request.getContextPath()%>/controller/UserLockController',{'userName':userName,'status':status}, function(data) { document.getElementById("status_"+userName).innerHTML=data; document.getElementById("td_"+userName).innerHTML=data; }); in servlet it writes as, out.println("<td id=\"status_"+inputParam+"\">Locked</td>"); out.println("<td id=\"td_"+inputParam+"\"><a href=\"#\" class=\"btn btn-sm btn-primary unlockBtn\" id=\"togBtn_"+inputParam+"\" onClick=\"LockAccount('"+inputParam+"','"+status+"')\">UnLock</td>"); Here content is returning but problem is the both <td> return from servlet will fit in single cell of html table. how to solve this please help me.

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  • Strange IP addresses in tomcat

    - by mdev
    Some where I have this in some generic class. public static String getRequestIp (HttpServletRequest request){ String ipaddr = request.getHeader("X-FORWARDED-FOR"); if (ipaddr == null)ipaddr = request.getRemoteAddr(); return ipaddr; } For every request i call that method and in a certain moment i insert a record in a mysql database. In most cases it works normally and i can see a record for every request with a valid ip address in the right field. But sometimes where the IP should be there is something like this. "unknown, 93.186.30.120" or "10.0.1.169, 186.38.84.3" Apache is at the front listening at port 80 and used as proxy to Tomcat that listens at port 8081. My router config would not allow to pass any conection that come by any port other than 80. Any Help? Thanks in advance.

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  • ANDROID : how to get value stored in ArrayList<HashMap<key,value>>?

    - by Roshni Kyada
    I have ArrayList. At another activity i want to access all values stored in ArrayList. I tried following code. ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>(); for(Hashmap<String, String> map: mylist) { for(Entry<String, String> mapEntry: map) { String key = mapEntry.getKey(); String value = mapEntry.getValue(); } } but it shows an error at for(Entry mapEntry: map) that it only interate over Array.

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  • Is Catching a Null Pointer Exception a Code Smell?

    - by Drew
    Recently a co-worker of mine wrote in some code to catch a null pointer exception around an entire method, and return a single result. I pointed out how there could've been any number of reasons for the null pointer, so we changed it to a defensive check for the one result. However, catching NullPointerException just seemed wrong to me. In my mind, Null pointer exceptions are the result of bad code and not to be an expected exception in the system. Are there any cases where it makes sense to catch a null pointer exception?

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  • Guice expert question

    - by Roman
    Hi All I am wondering if someone would be such an expert in guice that he even would know how to implement that : I have an injection annotation (@ConfParam)with some parameters , like that : class TestClass { private final int intValue; @Inject public TestClass(@ConfParam(section = "test1", key = "1") int intValue{ this.intValue = intValue; } public int getIntValue() { return intValue; } } The ConfParam is my custom annotation. Now , when the injection value is requested , I would like guice to create a dynamic binding, to resolve the value. For that binding I will need the parameters inside the annotation. Some example could be , I will have to look in the database in some table where the section is ? and the key is ?. All the trouble is that the data is not available when the injector is created and could be also be added at runtime. Ps. I static solution is easy. ( just have a look at the Names class)

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