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  • Design Pattern for Server Emulator

    - by adisembiring
    I wanna build server socket emulator, but I want implement some design pattern there. I will described my case study that I have simplified like these: My Server Socket will always listen client socket. While some request message come from the client socket, the server emulator will response the client through the socket. the response is response code. '00' will describe request message processed successfully, and another response code expect '00' will describe there are some error while processing the message request. IN the server there are some UI, this UI contain check response parameter such as. response code timeout interval While the server want to response the client message, the response code taken from input parameter response form UI check the timeout interval, it will create sleep thread and the interval taken from timeout interval input from UI. I have implement the function, but I create it in one class. I feel it so sucks. Can you suggest me what class / interface that I must create to refactor my code.

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  • How to identify the type of socket data?

    - by Nitesh Panchal
    Hello, May be i am not able to express my doubt properly in this question but still i will try. Basically i created a simple socket based chat program and everything works fine. But i think i have made many patches in it from the design point of view. I have used ObjectInputStream and ObjectOutputStreams in my program. The question i want to ask is how do i identify the different type of data that i send across the network? say if it is simple String type object i directly add to List<String> chatMessages. Now if want to ban certain users i created an another class :- public class User{ private String name; private String id; //getters and setters } This User class means no importance to me till now but i only created it to properly identify the action. Thus if i receive an instanceOf User i can be sure that some user is to be banned. That way i dont have to hardcode strings. I mean first i thought of sending something like "Banned User :" + userName and then i used to check if string startsWith "Banned User :" then i take some action :p. I've created a User class but it means no importance to me in my program. I want to know whether directly sending strings is good way or create a class for every action that is good. If i am not clear please let me know. If i have hundreds of action do i have to create hundreds of classes so i can check via instanceOf? Say now if i plan to create a BUZZ like facility that is available in yahoo messenger. Should i again create an another class named BUZZ? so it can be identified easily?

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  • Does HashMap provide a one to one correspondence?

    - by Roman
    I found the following statement: Map is an object that stores key/volume pairs. Given a key, you can find its value. Keys must be unique, but values may be duplicated. For example I have just one key/value pair (3,4). And now I put a new pair (3,5). It will remove the old pair. Right? But if I put (2,4) instead of (3,4) I will add a new pair of key/value to the HashMap. Right?

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  • How could I get an .ear's filesize at runtime?

    - by adam
    I started out attempting to do this with the Length ant task, but realized that that would be done before the ear is packaged. Packaging the ear, then checking the file size, and then placing it in the ear would effect the size of the ear. Is there a way to get the ear's size programmatically at run-time? Or perhaps an MBean that would have that information?

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  • Anybody using Qi4J

    - by Jon
    I was reading an InfoQ article on Composite Oriented Programming earlier on: http://www.infoq.com/articles/Composite-Programming-Qi4j I was interested in finding out whether anybody is currently using (or has used) the Qi4j framework at all? How does it compares to using a traditional dependency injection framework such as Spring for wiring classes together. Is the resulting object graph (based on mixins rather than classes) easier to deal with from a maintenance point of view?

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  • Check if there are any repeated elements in a array recursively

    - by devoured elysium
    I have to find recursively if there is any repeated element in an integer array v. The method must have the following signature: boolean hasRepeatedElements(int[] v) I can't see any way of doing that recursively without having to define another method or at least another overload to this method (one that takes for example the element to go after or something). At first I thought about checking for the current v if there is some element equal to the first element, then creating a new array with L-1 elements etc but that seems rather inefficient. Is it the only way? Am I missing here something?

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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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  • Creating lots of arrays

    - by Dmitry
    Hello, everybody! May be that is a stupid question. How to create, say, 30 arrays (it doesn't matter of what type, say, char[])? It seems to me that it is not a good idea, to create them one by one by hand. I want to do that using a "for" cycle, but how should I specify identifiers?

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  • Force close problem

    - by neetha-ann
    While i'm clicking a button in my menu list (for example select all)my application is getting force closed.Why is it so???in eclipse emulator it is working fine,but in phone(i'm using LG620)it's getting force closed,as i've no cable with me,i can't debug it.

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  • need help with parseInt

    - by cmona
    hello, how can i get for example the integer codeInt=082 from String code='A082' i have tried this: int codeInt = Integer.parseInt(code.substring(1,4)); and i get codeInt=82 ,it leaves the first 0 but i want the full code '082'. i thought of parseInt(String s, int radix) but i don't know how . any help will be appreciated . thanks.

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  • Can I fix the width of JRadioButton?

    - by Roman
    I have sever JPanels which have to be ordered vertically. For that I want to fix the width of the JPanels. Because if they are too short in comparison with the windows width, they will go horizontally (one after another) and I do not want it. At the moment the width of the JPanel is not constant because the width of the JRadioButton (included into JPabel) is not constant. How can I make the width of the JRadioButton constant? At the moment it is not constant because of the label (which can be different).

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  • Customizing error handling of JAXB unmarshall process

    - by ekeren
    Assuming I have a schema that describes a root element class Root that contains a List<Entry> where the Entry class has a required field name. Here is how it looks in code: @XmlRootElement class Root{ @XmlElement(name="entry") public List<Entry> entries = Lists.newArrayList(); } @XmlRootElement class Entry{ @XmlElement(name="name",required=true) public String name; } If I supply the following XML for unmarshalling: <root> <entry> <name>ekeren</name> </entry> <entry> </entry> </root> I have a problem because the second entry does not contain a name. So unmarshall produces null. Is there a way to customize JAXB to unmarshall a Root object that will only contain the "good" entry?

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  • How to initiate chatting between two clients and two clients only, using applets and servlets?

    - by mithun1538
    Hello everyone, I first need to apologize for my earlier questions. (You can check my profile for them)They seemed to ask more questions than give answers. Hence, I am laying down the actual question that started all them absurd questions. I am trying to design a chat applet. Till now, I have coded the applet, servlet and communication between the applet and the servlet. The code in the servlet side is such that I was able to establish chatting between clients using the applets, but the code was more like a broadcast all feature, i.e. all clients would be chatting with each other. That was my first objective when I started designing the chat applet. The second step is chatting between only two specific users, much like any other chat application we have. So this was my idea for it: I create an instance of the servlet that has the 'broadcast-all' code. I then pass the address of this instance to the respective clients. 2 client applets use the address to then chat. Technically the code is 'broadcast-all', but since only 2 clients are connected to it, it gives the chatting between two clients feature. Thus, groups of 2 clients have different instances of the same servlet, and each instance handles chatting between two clients at a max. However, as predicted, the idea didn't materialize! I tried to create an instance of the servlet but the only solution for that was using sessions on the servlet side, and I don't know how to use this session for later communications. I then tried to modify my broadcast-all code. In that code, I was using classes that implemented Observer and Observable interfaces. So the next idea that I got was: Create a new object of the Observable class(say class_1). This object be common to 2 clients. 2 clients that wish to chat will use same object of the class_1. 2 other clients will use a different object of class_1. But the problem here lies with the class that implements the Observer interface(say class_2). Since this has observers monitoring the same type of class, namely class_1, how do I establish an observer monitoring one object of class_1 and another observer monitoring another object of the same class class_1 (Because notifyObservers() would notify all the observers and I can't assign a particular observer to a particular object)? I first decided to ask individual problems, like how to create instances of servlets, using objects of observable and observer and so on in stackoverflow... but I got confused even more. Can anyone give me an idea how to establish chatting between two clients only?(I am using Http and not sockets or RMI). Regards, Mithun. P.S. Thanks to all who replied to my previous (absurd) queries. I should have stated the purpose earlier so that you guys could help me better.

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  • garbage collector Issue

    - by Eslam
    this question is like my previous one Given: 3. interface Animal { void makeNoise(); } 4. class Horse implements Animal { 5. Long weight = 1200L; 6. public void makeNoise() { System.out.println("whinny"); } 7. } 8. public class Icelandic extends Horse { 9. public void makeNoise() { System.out.println("vinny"); } 10. public static void main(String[] args) { 11. Icelandic i1 = new Icelandic(); 12. Icelandic i2 = new Icelandic(); 13. Icelandic i3 = new Icelandic(); 14. i3 = i1; i1 = i2; i2 = null; i3 = i1; 15. } 16. } When line 14 is reached, how many objects are eligible for the garbage collector? A. 0 B. 1 C. 2 D. 3 E. 4 F. 6 i choosed A but the right answer is E, but i don't know Why?

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  • Jetty RewriteHandler and RewriteRegexRule

    - by Justin
    I'm trying to rewrite a URL for a servlet. The URL gets rewritten correctly, but the context doesn't match after that. Any idea how to get this to work? RewriteHandler rewriteHandler = new RewriteHandler(); rewriteHandler.setRewriteRequestURI(true); rewriteHandler.setRewritePathInfo(true); rewriteHandler.setOriginalPathAttribute("requestedPath"); RewriteRegexRule rewriteRegexRule = new RewriteRegexRule(); rewriteRegexRule.setRegex("/r/([^/]*).*"); rewriteRegexRule.setReplacement("/r?z=$1"); rewriteHandler.addRule(rewriteRegexRule); ContextHandlerCollection contextHandlerCollection = new ContextHandlerCollection(); Context servletContext = new Context(contextHandlerCollection, "/"); servletContext.addServlet(new ServletHolder(new RedirectServlet()), "/r"); So basically /r/asdf gets rewritten to /r?z=asdf. However, the rewritten /r?z=asdf is now not processed by the servlet. Also, /r?z=asdf does work if called directly.

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  • JPA entity design / cannot delete entity

    - by timaschew
    I though its simple what I want, but I cannot find any solution for my problem. I'm using playframework 1.2.3 and it's using Hibernate as JPA. So I think playframework has nothing to do with the problem. I have some classes (I omit the nonrelevant fields) public class User { ... } public class Task { public DataContainer dataContainer; } public class DataContainer { public Session session; public User user; } public class Session { ... } So I have association from Task to DataContainer and from DataContainer to Sesssion and the DataContainer belongs to a User. The DataContainers can have always the same User, but the Session have to be different for each instance. And the DataContainer of a Task have also to be different in each instance. A DataContainer can have a Sesesion or not (it's optinal). I use only unidirectional assoc. It should be sufficient. In other words: Every Task must has one DataContainer. Every DataContainer must has one/the same User and can have one Session. To create a DB schema I use JPA annotations: @Entity public class User extends Model { ... } @Entity public class Task extends Model { @OneToOne(optional = false, cascade = CascadeType.ALL) public DataContainer dataContainer; } @Entity public class DataContainer extends Model { @OneToOne(optional = true, cascade = CascadeType.ALL) public Session session; @ManyToOne(optional = false, cascade = CascadeType.ALL) public User user; } @Entity public class Session extends Model { ... } BTW: Model is a play class and provides the primary id as long type. When I create some for each entity a object and 'connect them', I mean the associations, it works fine. But when I try to delete a Session, I get a constraint violation exception, because a DataContainer still refers to the Session I want to delete. I want that the Session (field) of the DataContainer will be set to null respectively the foreign key (session_id) should be unset in the database. This will be okay, because its optional. I don't know, I think I have multiple problems. Am I using the right annotation @OneToOne ? I found on the internet some additional annotation and attributes: @JoinColumn and a mappedBy attribute for the inverse relationship. But I don't have it, because its not bidirectional. Or is a bidirectional assoc. essentially? Another try was to use @OnDelete(action = OnDeleteAction.CASCADE) the the contraint changed from NO ACTIONs when update or delete to: ADD CONSTRAINT fk4745c17e6a46a56 FOREIGN KEY (session_id) REFERENCES annotation_session (id) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE CASCADE; But in this case, when I delete a session, the DataContainer and User is deleted. That's wrong for me. EDIT: I'm using postgresql 9, the jdbc stuff is included in play, my only db config is db=postgres://app:app@localhost:5432/app

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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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  • How do I determine whether I am going "forward" or "backward" through my History in GWT?

    - by Stephen Cagle
    I am looking at History and History JavaDocs in GWT and I notice that there is no way to tell whether the forward or backward button was pressed (either pragmatically or by the user). The "button press" is handled by your registered addValueChangeHandler, but the only thing passed to the handler is a string on your history stack. There is no indication as to whether the "History" is moving "back" (using the back arrow button) or "forward" (using the right arrow button). Is there any way to determine this?

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  • MySQL best usage in Tomcat?

    - by mabuzer
    Which one is better way of using MySQL in Tomcat : A) assign a DB connection for user as long as it's session is valid. [OR] B) open connection to DB, on every request come to server and when it's done close that. ?

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  • ListView OnItemClickListener Not Responding?

    - by GuyNoir
    I've looked everywhere for a solution to this, but I can't figure out how to implement it. My OnItemClickListener was disabled somehow on my ListView rows, because I have an ImageButton in the row layout, which takes over the focus. There have been numerous questions I've found, but none of them have gotten me anywhere. I've checked this question, but I couldn't really make heads or tails of it. I just need a way to get the rows clickable so that I can detect when a row is pressed. Long press and focus work fine.

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