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  • Why isn't JML implemented as Annotations in Java?

    - by devoured elysium
    Contrary to Code Contracts in C#, in JML Code Contracts are just text that's used in the form of comments in the header of a method. Wouldn't it be better to have them exposed as Annotations, then? That way even when compiling the information would persist on the .class's metadata, contrary to comments, that get erased. Am I missing something? Thanks

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  • Passing Interface Class as a Parameter in Java

    - by aleclerc
    I have an interface: public interface IMech { } and a class that implements it public class Email implements IMech { } and a third class that has this method implemented: public void sendNotification( Class< IMech > mechanism ){ } now I'm trying to call that method like so foo.sendNotification(Email.class); but i keep getting an exception saying: The method sendNotification(Class<IMechanism>) in the type RemediationOperator is not applicable for the arguments (Class<EmailNotification>) Shouldn't this work if it interfaces that class?

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  • Java Interfaces

    - by Mandar
    I have a doubt.. Why do we need interfaces ? Can't we acheive the same effect by writing the implementation directly in the class? It would be great if you could illustrate your point with an example. Thanks in advance.

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  • Java EE deployment error

    - by Rajesh
    While deploying a particular project I'm getting deployment error like "module has not been deployed"... but I'm able to deploy other projects... the error shown is as follows In-place deployment at F:\onlineexam_1\build\web deploy?path=F:\onlineexam_1\build\web&name=onlineexam_1&force=true failed on GlassFish v3 Domain F:\onlineexam_1\nbproject\build-impl.xml:577: The module has not been deployed. BUILD FAILED (total time: 3 seconds)

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  • Fastest Java web templating language

    - by CaptainAwesomePants
    I'm about to start in on a new Spring MVC project, and I'm examining the various options for the view. I've never been a fan of JSP, and I've run into JSP-related performance problems in the past, so I was looking through the other options. I'm hoping that somewhere somebody's taken a census of the various options (maybe it'll have to be me) and pronounced which ones are quick, or at least which options there are. Here are the choices I've thought of, ordered from obvious to bizarre: JSP, JSTL Velocity FreeMarker GSP (Groovy JSP) ERB powered by IronRuby or some such craziness Tea Any suggestions, personal preferences, or other good options for the list?

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  • How can i zip files in Java and not include files paths

    - by Ignacio
    For example, i want to zip a file stored in /Users/me/Desktop/image.jpg I maded this method: public static Boolean generateZipFile(ArrayList<String> sourcesFilenames, String destinationDir, String zipFilename){ // Create a buffer for reading the files byte[] buf = new byte[1024]; try { // VER SI HAY QUE CREAR EL ROOT PATH boolean result = (new File(destinationDir)).mkdirs(); String zipFullFilename = destinationDir + "/" + zipFilename ; System.out.println(result); // Create the ZIP file ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFullFilename)); // Compress the files for (String filename: sourcesFilenames) { FileInputStream in = new FileInputStream(filename); // Add ZIP entry to output stream. out.putNextEntry(new ZipEntry(filename)); // Transfer bytes from the file to the ZIP file int len; while ((len = in.read(buf)) > 0) { out.write(buf, 0, len); } // Complete the entry out.closeEntry(); in.close(); } // Complete the ZIP file out.close(); return true; } catch (IOException e) { return false; } } But when i extract the file, the unzipped files have the full path. I don't want the full path of each file in the zip i only want the filename. How can i made this?

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  • What's the standard way to organize the contents of Java packages -- specifically the location of in

    - by RenderIn
    I suppose this could go for many OO languages. I'm building my domain objects and am not sure where the best place is for the interfaces & abstract classes. If I have a pets package with various implementations of the APet abstract class: should it live side-by-side with them or in the parent package? How about interfaces? It seems like they almost have to live above the implementations in the parent package, since there could potentially be other subpackages which implement it, while there seems to be a stronger correlation between one abstract class and a subpackage. e.g. com.foo com.foo.IConsumer (interface) com.foo.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer OR com.foo com.foo.IConsumer (interface) com.foo.pets.APet (abstract) com.foo.pets.Dog extends APet implements IConsumer or something else?

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  • http streaming using java servlet

    - by Shamik
    I have a servlet based web application which produces two sets of data. One set of data in the webpage which is essential and other set which is optional. I would like to render the essential data as fast as possible and then stream the optional data. I was thinking of writing the essential data to the output stream of HttpServletRequest and then call HttpServletRequest.flushBuffer() to commit the response to the client, but do not return from the servlet code, but instead create the optional data , write that to the outputstream again and then return from servlet code. What are the things that could go wrong in this scheme ? Is this a standard practice to achieve this goal?

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  • Bluetooth in Java Mobile: Handling connections that go out of range

    - by Albus Dumbledore
    I am trying to implement a server-client connection over the spp. After initializing the server, I start a thread that first listens for clients and then receives data from them. It looks like that: public final void run() { while (alive) { try { /* * Await client connection */ System.out.println("Awaiting client connection..."); client = server.acceptAndOpen(); /* * Start receiving data */ int read; byte[] buffer = new byte[128]; DataInputStream receive = client.openDataInputStream(); try { while ((read = receive.read(buffer)) > 0) { System.out.println("[Recieved]: " + new String(buffer, 0, read)); if (!alive) { return; } } } finally { System.out.println("Closing connection..."); receive.close(); } } catch (IOException e){ e.printStackTrace(); } } } It's working fine for I am able to receive messages. What's troubling me is how would the thread eventually die when a device goes out of range? Firstly, the call to receive.read(buffer) blocks so that the thread waits until it receives any data. If the device goes out of range, it would never proceed onward to check if meanwhile it has been interrupted. Secondly, it would never close the connection, i.e. the server would not accept the device once it goes back in range. Thanks! Any ideas would be highly appreciated! Merry Christmas!

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  • Java Web Application on Tomcat - Displaying a File Uploaded by User

    - by walnutmon
    I need to display uploaded files on a web application, the flow is as follows User uploads file through web UI Validation on image Makes call to imageRepository.store( uploadedImage, user.getSite() ) The user wants the image displayed which adds <img src="${anUploadedImage.getUrl()}"/> but that is where I'm stuck, what can getUrl() do? The simple solution is to put it someplace and let Apache serve the file, but then I can't use the application to ensure that one user isn't modifying the URL to view other users files, which in this case is important

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  • What are the essential Java libraries and utilities for a returning dynamic language user?

    - by jbwiv
    Guys, Long time Java developer here, but I've spent more time working with Ruby over the past 3 years or so as far as web applications go. I really have enjoyed it, but there are concerns I've uncovered that I won't cover here. Now that I've found the Play! framework, I'm thrilled about the prospect of having a Rails-like experience with Java's speed and reliability. Aside from what Play! provides out of the box, I'm looking for recommendations on "can't miss" libraries and tools for the Java developer used to pragmatic, dynamic experiences. I've found Project Lombok, which looks like a very intriguing way to eliminate a lot of the boiler plate, unnecessary Java noise. What else should I know about? I know Google has released quite a few libraries over the past three years that I've heard mentioned on the Java Posse, but I can't recall exactly what they are. I'm sure I've missed others in my absence. So, what makes up your essential Java toolbox these days? Thanks for your answers!

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  • HTML-like GUI Framework in Java

    - by wintermute
    I was recently brought onto a project where we are developing a lot GUI elements for BlackBerry devices. The standard RIM APIs are pretty basic, almost never do what is required and are difficult or impossible to extend, so we end up re-implementing chunks of it. Currently the code we have isn't super organized and factored so there are lots of little tricks that get implemented over and over again. I had a thought about how to aid development efforts on this platform and wanted to see if the community could tell me if I'm still sane or if I've gone totally nuts. By far, the biggest organizational problem I've run into is making sure that each screen is laid out properly with proper padding and such. The current approach is to manually keep track of padding like so: protected void sublayout(int width, int height) { final int padding = 5; int y = padding; int x = padding; layoutChild(_someChild, width - padding * 2, height / 3 - padding * 2); setPositionChild(_someChild, x, y); y += _someChild.getHeight() + padding; // Calculate where to start drawing next. /* ... snipped ... */ } As you can see, positioning elements on a screen is a nightmare due to the tedium. I have investigated other GUI frameworks but, for a variety of reasons, it is difficult to find one that suites our purposes. One potential solution that came to me is to create a GUI framework who's API resembles HTML/CSS. This would allow for things like padding, margins, borders and colours to be handled through a sort of CSS API while the content would be organized using the HTML part of the API. It might look something like this: public class OptionsScreen extends Document { public OptionsScreen() { // You would set the style (like CSS style) through the constructor. Div content = new Div(new Style(new Padding(5), Color.BLACK)); // Then build up a tree of elements which can each have their own style's. // Each element knows how to draw itself, but it doesn't have to worry about // manually handling things like padding. // content.addChild(new P("This is a paragraph", new Style(new Padding(), Color.RED))); Ul list = new Ul(); list.addChild(new Li("item 1")); list.addChild(new Li("item 2")); content.addChild(list); addChild(content); } } I can imagine this making it easier to customize the UI of our app (which is very important) with different fonts, colours and layouts. Does this idea belong on The Daily WTF or do you think there is some promise?

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  • Unique serial number in a java web application.

    - by Zenzen
    I've been wondering what's the correct practice for generating unique ids? The thing is in my web app I'll have a plugin system, when a user registers a plugin I want to generate a unique serial ID for it. I've been thinking about storing all numbers in a DB or a file on the server, generating a random number and checking whether it already exists in the DB/file, but that doesn't seem that good. Are there other ways to do it? Would using the UUID be the preferred way to go?

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  • Best OpenID library for Java

    - by Adam Crume
    I want users to be able to log into my website with OpenID, but I don't know which library to use. I know which ones are out there, but I would like to know which one would be best. I'm running JOnAS, but no web framework (no Spring, Struts, GWT, etc.). (Please don't chastise me for not using a web framework. I have my reasons.) For what it's worth, my web site is broken into multiple WARs, and I would prefer something that works well in that situation, but that's not a big deal. Does anyone have experience with the different libraries? Any experiences or wisdom you can share?

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  • Do we need seperate file path for window and linux in java

    - by Kishor Sharma
    I have a file on linux ubuntu server hosted with path name /home/kishor/project/detail/. When I made a web app in window to upload and download file from specified location i used path "c:\kishor\projects\detail\" for saving in window. For my surprise when i used window file path name in my server i am still able to get files and upload them, i.e, "c:\kishor\projects\detail\". Can anyone explain why it is working (as window and linux both use different file path pattern).

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  • How would you code an efficient Circular Buffer in Java or C#

    - by Cheeso
    I want a simple class that implements a fixed-size circular buffer. It should be efficient, easy on the eyes, generically typed. EDIT: It need not be MT-capable, for now. I can always add a lock later, it won't be high-concurrency in any case. Methods should be: .Add and I guess .List, where I retrieve all the entries. On second thought, Retrieval I think should be done via an indexer. At any moment I will want to be able to retrieve any element in the buffer by index. But keep in mind that from one moment to the next Element[n] may be different, as the Circular buffer fills up and rolls over. This isn't a stack, it's a circular buffer. Regarding "overflow": I would expect internally there would be an array holding the items, and over time the head and tail of the buffer will rotate around that fixed array. But that should be invisible from the user. There should be no externally-detectable "overflow" event or behavior. This is not a school assignment - it is most commonly going to be used for a MRU cache or a fixed-size transaction or event log.

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  • Implementing OAuth protocol in Java

    - by Wasim
    Hi all , I'm looking for an open source library that implements the OAuth protocol , I need the server side implementation . Say I have a Social network system , and I want to give my users an OAth abiliy to my API , like facebook. Do you have any suggestion , sure examples . Thanks in advance ...

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  • Java Executor: Small tasks or big ones?

    - by Arash Shahkar
    Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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  • How to avoid resetting the java Scanner position

    - by Derek
    I have some code that looks more or less like this: while(scanner.hasNext()) { if(scanner.findInLine("Test") !=null) { //do some things }else{ scanner.nextLine(); } } I am using this to parse an ~10MB text file. The problem is, if I put a breakpoint on the while() and the scanner.nextLine(), I can see that sometimes the scanners position (in the debug window) goes back to zero. I think this is causing me some kind of loop blow up, because the regext in findInLine() starts at zero, looks through some amount of text, advancing the position, and then it randomly gets set back to zero, so it has to re-parse all that text again. Any ideas what can be causing that? Am I even doing this the right way? Thanks Some additional info: The Scanner is instantiated from an InputStream. After diubg sine debugging, it appears that there is a HearCharBuffer that Scanner uses and it only allows 1024 characters at a time, and then resets. Is there a way to avoid this, or do things differently? That seems like a small amount of characters to be able to scan. Derek

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  • Dealing With Java Default Level Access Specifiers

    - by Tom Tresansky
    I've seen some code in a project recently where some fields in a couple classes have been using the default access modifier without good reason to. It almost looks like a case of "oops, forgot to make these private". Since the classes are used almost exclusively outside of the package they are defined in, the fields are not visible from the calling code, and are treated as private. So the mistake/oversight would not be very noticeable. However, encapsulation is broken. If I wanted to add a new class to the existing package, I could then mess with internal data in objects using fields with default access. So, my questions: Are there any best practices concerning default access specifiers that I should be aware of? Anything that would help prevent this type of accident from re-occurring? Are are any annotations which might say something to the effect of "I really meant for these to be default access"? Using CheckStyle, or any other Eclipse plugins, is there any way to flag instances of default fields, or disallow any not accompanied by, say, a "//default access" comment trailing them?

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  • Make Java parent class not part of the interface

    - by Bart van Heukelom
    (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

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  • Java - How to change context root of a dynamic web project in eclipse

    - by Yatendra Goel
    I have developed a dynamic web project in eclipse. Now I can access it through my browser using the following url: http://localhost:8080/MyDynamicWebApp Now I want to change the access url to http://localhost:8080/app I changed the context root from the project properties | Web Project Settings | Context Root But it is not working. The web app still has the access url as earlier. I have re-deployed the application on tomcat, re-started the tomcat and have done everything that should be done but the access url is the same as earlier. I found that there were no server.xml file attached with the WARfile. The how the tomcat is determining that the context root of my web app is /MyDynamicWebApp and is allowing me to access the application through that url

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  • Why doesn't Java Map extends Collection?

    - by polygenelubricants
    I was surprised by the fact that Map<?,?> is not a Collection<?>. I thought it'd make a LOT of sense if it was declared as such: public interface Map<K,V> extends Collection<Map.Entry<K,V>> After all, a Map<K,V> is a collection of Map.Entry<K,V>, isn't it? So is there a good reason why it's not implemented as such?

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  • Fastest way to learn Flex and Java EE?

    - by LostWebNewbie
    Ok so me and my 2 friends have to make a webapp and well we think it's a good opportunity to learn JEE and Flex. The thing is we have very little knowledge about them and we have only 3 months to do it (it doesn't have to be super complicated). So my question is: what, in your opinion, would be the fastest way to learn them both? I guess we need to know some JSP, Serlvets, JPA (??), Flex, maybe JavaScript+CSS? Anything else like EJB? Should we also learn Spring (or Struts)? Obviously reading books would be a good idea, but I bet we won't make the deadline if we try to read all the books... @Edit: I know the basics of JSP/Servlets (read Head First JSP&Servlets) but I made only 1 project so far (a semi-decent hangman with JSP/Serlvets and JPA for persistance) that's about it. Flex - I'm just starting, I know really the basics of mxml and as3. As for why: 1) because we need to do a project for the uni and well I was thinking bout becoming a web dev (yup - jee+flex) after graduation, this is the perfect opportunity to learn them.

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  • Recommendations for java captcha libraries

    - by skaffman
    I'm looking for a replacement for JCaptcha, which doesn't seem to be maintained any more, and isn't very good to begin with. The replacement has to integrate nicely with JavaEE webapps. As I can see it, there are three options: JCaptcha - No longer maintained, crude API SimpleCaptcha - much nicer API, nicer captchas, but seems to be Java6 only ReCaptcha - easy to use, uses remote web-service to generate captchas, but not much control over look and feel Has anyone used any others, that they'd recommend?

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