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  • Correct use of Classloader (especially in Android)

    - by Sebi
    I read some documentations about classloaders, but im still not sure where and why they are needed. The Android API says: Loads classes and resources from a repository. One or more class loaders are installed at runtime. These are consulted whenever the runtime system needs a specific class that is not yet available in-memory. So if i understand this correct, there can be many classlaoders which are responsible for loading new classes. But how the system decides which to use? And in which situation should a developer instantiate a new classloader? In the Android API for Intent there is a method public void setExtrasClassLoader (ClassLoader loader) The description says: Sets the ClassLoader that will be used when unmarshalling any Parcelable values from the extras of this Intent. So can i define there a special classloader so that i can pass object with an Intent which are not defined in the receiving activity? An example: If activity A which is located in Project A (in Eclipse) defines an object which i want to send to Activity B in Project B using putExtra of the Intent object. If this object which is send over the Intent is not defined (source code in project B), then there is a NoClassDefFoundException. So can i use the method setExtraClassloader to avoid this exception? If yes, how can i decide which classloader object i have to pass? And how do I instantiate it correctly?

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  • Putting Select Statement on Hibernate Transaction

    - by Mark Estrada
    Hi All, I have been reading the net for a while regarding Hibernate but I can seem to understand one concept regarding Transaction. On some site that I have visit, Select statements are in transaction mode like this. public List<Book> readAll() { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); session.beginTransaction(); List<Book> booksList = session.createQuery("from Book").list(); session.getTransaction().commit(); return booksList; } While on some site, it does not advocate the use of transaction on Select statements public List<Book> readAll() { Session session = HibernateUtil.getSessionFactory() .getCurrentSession(); List<Book> booksList = session.createQuery("from Book").list(); return booksList; } I am thinking which one should I follow. Any thoughts please? Are transactions needed on Select Statements or not? Thanks

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  • AdMob Android integration - what permissions to ask for?

    - by AngryHacker
    In the various videos on the AdMob integration, I've seen that only permission to access the internet is asked for: <uses-permission android:name="android.permission.INTERNET" /> Not that I am an expert in advertising, but wouldn't AdMob need the user's geographic location as well, so that they can serve location specific ads? Or avoid serving certain ads based on a location, like maybe not offering me a Big Mac if I am in India or not adverting a ham sandwich if I am in an Arab country? If AdMob needs those permissions, how do I ask for them?

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  • Efficient representation of Hierarchies in Hibernate.

    - by Alison G
    I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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  • NullPointerException when trying to add an object to a PriorityQueue

    - by meagan
    i keep getting a null pointer exception when trying to add an object to a priority queue i initialize the queue: private PriorityQueue<NodeObject> nodes; and here i try to add to it: NodeObject childNode = new NodeObject(child, 1); nodes.add(childNode); why doesn't this work? i know my NodeObject is not null because i create it right before i add it.

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  • Yet another Ant + JUnit classpath problem

    - by user337591
    Hi, I'm developing an Eclipse SWT application using Eclipse. There are also some JUnit 4 tests, which test some DAO's. But when I try to run the tests via an ant build, all of the tests fail, because the test classes aren't found. Google brought up about a million of people who all have the same problem, but none of their solutions seem to work for me -.- . These are the contents of my build.xml file: <property name="test.reports" value="./test/reports" /> <property name="classes" value="build" /> <path id="project.classpath"> <pathelement location="${classes}" /> </path> <target name="testreport"> <mkdir dir="${test.reports}" /> <junit fork="yes" printsummary="no" haltonfailure="no"> <batchtest fork="yes" todir="${test.reports}" > <fileset dir="${classes}"> <include name="**/Test*.class" /> </fileset> </batchtest> <formatter type="xml" /> <classpath refid="project.classpath" /> </junit> <junitreport todir="${test.reports}"> <fileset dir="${test.reports}"> <include name="TEST-*.xml" /> </fileset> <report todir="${test.reports}" /> </junitreport> </target> The test classes are in the build-directory together with the application classes, although they are in some subfolders according to their packages. Maybe this is important too: At first Ant complained that JUnit wasn't in its classpath, but since I put it there (with the eclipse configuration editor) it complains about JUnit being in its classpath twice. WARNING: multiple versions of ant detected in path for junit [junit] jar:file:C:/Users/as df/Documents/eclipse/plugins/org.apache.ant_1.7.1.v20090120-1145/lib/ant.jar!/org/apache/tools/ant/Project.class [junit] and jar:file:/C:/Users/as%20df/Documents/eclipse/plugins/org.apache.ant_1.7.1.v20090120-1145/lib/ant.jar!/org/apache/tools/ant/Project.class I've tried specifying each and every subdirectory, each and every class file, I've tried filesets and filelists, nothing seems to work. Thanks for your help, I've been sitting for hours on this thing now...

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  • Making change recursively: How do I modify my algorithm to print all combinations?

    - by cb
    I have an algorithm that recursively makes change in the following manner: public static int makeChange(int amount, int currentCoin) { //if amount = zero, we are at the bottom of a successful recursion if (amount == 0){ //return 1 to add this successful solution return 1; //check to see if we went too far }else if(amount < 0){ //don't count this try if we went too far return 0; //if we have exhausted our list of coin values }else if(currentCoin < 0){ return 0; }else{ int firstWay = makeChange(amount, currentCoin-1); int secondWay = makeChange(amount - availableCoins[currentCoin], currentCoin); return firstWay + secondWay; } } However, I'd like to add the capability to store or print each combination as they successfully return. I'm having a bit of a hard time wrapping my head around how to do this. The original algorithm was pretty easy, but now I am frustrated. Any suggestions? CB

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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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  • Timer Service in ejb 3.1 - schedule calling timeout problem

    - by Greg
    Hi Guys, I have created simple example with @Singleton, @Schedule and @Timeout annotations to try if they would solve my problem. The scenario is this: EJB calls 'check' function every 5 secconds, and if certain conditions are met it will create single action timer that would invoke some long running process in asynchronous fashion. (it's sort of queue implementation type of thing). It then continues to check, but as long as long running process is there it won't start another one. Below is the code I came up with, but this solution does not work, because it looks like asynchronous call I'm making is in fact blocking my @Schedule method. @Singleton @Startup public class GenerationQueue { private Logger logger = Logger.getLogger(GenerationQueue.class.getName()); private List<String> queue = new ArrayList<String>(); private boolean available = true; @Resource TimerService timerService; @Schedule(persistent=true, minute="*", second="*/5", hour="*") public void checkQueueState() { logger.log(Level.INFO,"Queue state check: "+available+" size: "+queue.size()+", "+new Date()); if (available) { timerService.createSingleActionTimer(new Date(), new TimerConfig(null, false)); } } @Timeout private void generateReport(Timer timer) { logger.info("!!--timeout invoked here "+new Date()); available = false; try { Thread.sleep(1000*60*2); // something that lasts for a bit } catch (Exception e) {} available = true; logger.info("New report generation complete"); } What am I missing here or should I try different aproach? Any ideas most welcome :) Testing with Glassfish 3.0.1 latest build - forgot to mention

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  • Accelerometer Values from Android/iPhone device

    - by mrlinx
    I'm trying to map my movements with a android device into an OpenGL scene. I've recorded accelerometer values for a simples movement: Moving the phone (lies flat on a table) 10cm forward (+x), and then 10cm backward (-x). The problem is that this values when used to calculate velocity and position, makes only the opengl cube go forward. Seems like the negative acceleration recorded was not enough to reduce the speed and invert its movement. What can be the problem? This is my function that updates the velocity and position every time new data comes in: void updatePosition(double T2) { double T = 0.005; Vec3 old_pos = position.clone(), old_vel = velocity.clone(); velocity = old_vel.plus(acceleration.times(T)); position = old_pos.plus(old_vel.times(T).plus(acceleration.times(0.5 * Math.pow(T, 2)))); } This is the X,Y,Z accelerometer values over the entire captured time:

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  • Spring Transactional Parameterized Test and Autowiring

    - by James Kingsbery
    Is there a way to get a class that extends AbstractTransactionalJUnit4SpringContexts to play nicely with JUnit's own @RunWith(Parameterized), so that fields marked as Autowired get wired in properly? @RunWith(Parameterized) public class Foo extends AbstractTransactionalJUnit4SpringContexts { @Autowired private Bar bar @Parameters public static Collection data() { // return parameters, following pattern in // http://junit.org/apidocs/org/junit/runners/Parameterized.html } @Test public void someTest(){ bar.baz() //NullPointerException } }

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  • Partially constructed object / Multi threading

    - by reto
    Heya! I'm using joda due to it's good reputation regarding multi threading. It goes great distances to make multi threaded date handling efficient, for example by making all Date/Time/DateTime objects immutable. But here's a situation where I'm not sure if Joda is really doing the right thing. It probably is correct, but I'd be very interested to see the explanation for it. When a toString() of a DateTime is being called Joda does the following: /* org.joda.time.base.AbstractInstant */ public String toString() { return ISODateTimeFormat.dateTime().print(this); } All formatters are thread safe, as they are as well ready-only. But what's about the formatter-factory: private static DateTimeFormatter dt; /* org.joda.time.format.ISODateTimeFormat */ public static DateTimeFormatter dateTime() { if (dt == null) { dt = new DateTimeFormatterBuilder() .append(date()) .append(tTime()) .toFormatter(); } return dt; } This is a common pattern in single threaded applications. I see the following dangers: Race condition during null check -- worst case: two objects get created. No Problem, as this is solely a helper object (unlike a normal singleton pattern situation), one gets saved in dt, the other is lost and will be garbage collected sooner or later. the static variable might point to a partially constructed object before the objec has been finished initialization (before calling me crazy, read about a similar situation in this Wikipedia article. So how does Joda ensure that not partially created formatter gets published in this static variable? Thanks for your explanations! Reto

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  • Using a Session Scoped Bean

    - by jboyd
    The following code is returning null: private MyAppUser getMyAppUser(HttpSession session) { MyAppUser myAppUser = (MyAppUser) session.getAttribute("myAppUserManager"); return myAppUser; } Despite the fact that I have the following in my context: <bean id="myAppUserManager" class="com.myapp.profile.MyAppUser" scope="session"/> This doesn't make any sense to me, the "myAppUser" bean is a bean that absolutely can never be null, and I need to be able to reference it from controllers, I don't need it in services or repositories, just controllers, but it doesn't seem to be getting stored in the session, the use case is extremely simple, but I haven't been able to get to the bottom of what's wrong, or come up with a good workaround

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  • Add objects to Arraylist inside loop and get a list of them outside loops

    - by AgusDG
    Im already done with a method to do a shot on a board (bidimensional array). THe shot goes from the bottom to the top, and depending of the direction, it do bounces on the walls to get to the top. The thing is that I did the method to represent the trayectory with an 'x'. Now, I want to add the coordinates x and y of each position of the shot (b [x][y]) to and Arraylist of Objects Position. public Position(int row,int col) { this.row = row; this.col = col; } The thing is that the method uses a for loop and inside if loops, and I'll need to create the objects inside, and get them outside. I did that : public static ArrayList<Position> showTrayectory (char [][] b , int shotDirection, char bubble){ int row = 0, col = 0; ArrayList<Position> aListPos = new ArrayList<Position>(); Position positionsOfShot = new Position(row,col); START = ((RIGHT_WALL)/2) + shotDirection; boolean shotRight = false; if(shotDirection < 0) shotRight = false; else if(shotDirection > 0) shotRight = true; for(int y = BOTTOM,x = START ;y >= 0;y--) { if(!isOut(y,x) && !emptyCell(y,x)) break; if(x <= LEFT_WALL) shotRight = true; if(x >= RIGHT_WALL) shotRight = false; if(!isOut(y,x) && shotRight == true) { positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; ++x; } if(!isOut(y,x) && shotRight == false){ positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; --x; } } // The nested for loops below are for showing the positions // But I dont need it that way // I must get the trayectory from an ArrayList and print it from there for(int y=0;y < b.length;y++){ System.out.println(); for(int x=0;x < b[y].length;x++){ System.out.print(" "+b [y][x]+" "); } } System.out.println("\nTrayectory of the shot ["+shotDirection+"]"); System.out.println("Next bubble ["+bubble+"]"); for( Position ii : aListPos){ System.out.println("(" + positionsOfShot.getFila() + "," + positionsOfShot.getColumna()+")"); } return aListPos; } The sentence " b[y][x] = SHOT; " is still there, to see the proper trayectory of the shot (its not needed that way), but what I need, is getting the trayectory in an ArrayList, and print the trayectory from there. All that I get is a wrong position, and repeated during the number of positions the shot goes through. I need some help. I suppose the problem is that Im creating and adding Position Objects inside an ArrayList inside loops, but in a wrong way. I will need you to explain me how to do it properly ; ) Thanks in advance. I'll add the output for you see better what is that above haha *************************** y b y b g r b g o y g a a r y o y y r b y g r r o b o y y g b a r y r o a y y o o r r g r - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - x - - - - - - - x - - - - - - - x - - - Trayectory of the shot [1] Next bubble [y] (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) Action?

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  • Caching Authentication Data

    - by PartlyCloudy
    Hi, I'm currently implementing a REST web service using CouchDB and RESTlet. The RESTlet layer is mainly for authentication and some minor filtering of the JSON data served by CouchDB: Clients <= HTTP = [ RESTlet <= HTTP = CouchDB ] I'm using CouchDB also to store user login data, because I don't want to add an additional database server for that purpose. Thus, each request to my service causes two CouchDB requests conducted by RESTlet (auth data + "real" request). In order to keep the service as efficent as possible, I want to reduce the number of requests, in this case redundant requests for login data. My idea now is to provide a cache (i.e.LRU-Cache via LinkedHashMap) within my RESTlet application that caches login data, because HTTP caching will probabily not be enough. But how do I invalidate the cache data, once a user changes the password, for instance. Thanks to REST, the application might run on several servers in parallel, and I don't want to create a central instance just to cache login data. Currently, I save requested auth data in the cache and try to auth new requests by using them. If a authentication fails or there is now entry available, I'll dispatch a GET request to my CouchDB storage in order to obtain the actual auth data. So in a worst case, users that have changed their data will perhaps still be able to login with their old credentials. How can I deal with that? Or what is a good strategy to keep the cache(s) up-to-date in general? Thanks in advance.

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  • using internationalization on list data

    - by singh
    i am using Struts2 in application. <s:iterator value="listObject"> <s:component template="abc.vm"> <s:param name="text" value="listValue" /> <s:param name="prefix" value="listIndex" /> </s:component> </s:iterator> listValue is a values of list. i am using iterator to traverse the list. now on listValue, i want to put here internationalization concept.so that all the list value can be display based on Locale which store in a list. please suggest!

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  • Setting Mnemonics and Hot Keys for a JOptionPane Dialog

    - by Daniel Bingham
    Is it possible to assign hotkeys and mnemonics to the buttons in a JOptionPane Dialog? I'd like to be able, in a JOptionPane generated message dialog with the options Yes, No and Cancel, press Y to hit the Yes button, N to hit the No button and escape to activate the escape button. Similarly in a dialog with Okay and Cancel buttons I'd like to be able to activate them with enter and escape. I've attempted passing JButtons into the JOptionPane's button Object array with the Mnemonics set already. The mnemonics work and the buttons show up correctly in the dialogs, however, they do not act properly when they are activated. Most noticeably they do not dispose of the dialog. What is the correct way to add hotkeys and Mnemonics to a JOptionPane Dialog's buttons? As always, my apologies ahead of time if this is a duplicate - I searched both Google and Stackoverflow and found nothing.

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  • Access JBOSS Tomcat Web Application from Remote Computer

    - by Rod
    Hi, I just deployed a web application on JBOSS 4.2. It can be accessed locally only (http://localhost:8080/myApp). I cant access it from remote computer by typing its domain: (www.hostname.com:8080/myApp). I added Port 8080 as Exception in Windows Firewall. Note that the host (www.hostname.com) is reachable from remote computers via IIS on port 80. Thanks, Rod

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  • JTable custom cell renderer to create row header

    - by hhj
    Can somebody please explain how I would create row headers? I already have the data and header texts set in the JTable: all I want to know is how I can use a cell renderer to take that first column (i.e. the row header column) and make it look like the column headers (i.e. the first row). Right now its background is white, so it looks like regular data. I want it to appear gray (or non-opaque I guess??). Oh and it should also not be selectable. Thanks.

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  • Spring MVC 3 - How come @ResponseBody method renders a JSTLView?

    - by Ken Chen
    I have mapped one of my method in one Controller to return JSON object by @ResponseBody. @RequestMapping("/{module}/get/{docId}") public @ResponseBody Map<String, ? extends Object> get(@PathVariable String module, @PathVariable String docId) { Criteria criteria = new Criteria("_id", docId); return genericDAO.getUniqueEntity(module, true, criteria); } However, it redirects me to the JSTLView instead. Say, if the {module} is product and {docId} is 2, then in the console I found: DispatcherServlet with name 'xxx' processing POST request for [/xxx/product/get/2] Rendering view [org.springframework.web.servlet.view.JstlView: name 'product/get/2'; URL [/WEB-INF/views/jsp/product/get/2.jsp]] in DispatcherServlet with name 'xxx' How can that be happened? In the same Controller, I have another method similar to this but it's running fine: @RequestMapping("/{module}/list") public @ResponseBody Map<String, ? extends Object> list(@PathVariable String module, @RequestParam MultiValueMap<String, String> params, @RequestParam(value = "page", required = false) Integer pageNumber, @RequestParam(value = "rows", required = false) Integer recordPerPage) { ... return genericDAO.list(module, criterias, orders, pageNumber, recordPerPage); } Above do returns correctly providing me a list of objects I required. Anyone to help me solve the mystery?

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  • Semantic stuff (RDF, OWL) on mobile phones - is it possible?

    - by Brian Schimmel
    I'm thinking about using semantic (web) technogies like RDF and OWL in an application on mobile devices. Currently I'm targeting android, but I'd also be interested in the possibilities on the iPhone and on J2ME. I would like to use a lib instead of implementing everything from scratch. I know that there are some libraries and frameworks like Jena, Redland, Protégé but they don't state on which platforms they are known to work. Having a dynamic object model and parsing from and to XML are must-haves for me. I'd also like to use reasoning, but I've been told it was rather computing-intensive, so that's only a nice-to-have. For all platforms mentioned, the question can be interpreted as Is it possible in theory (especially for J2ME I'm not sure) Are there libs that are known to work on those platforms? Is the performance on a mobile platform good enough for real world usage?

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  • Swing's KeyListener and multiple keys pressed at the same time.

    - by Negai
    Hi everyone, is there any conventional way in swing of tracking down the events, when two keyboard keys are pressed at the same time? I have a couple of ideas e.g. remembering the key and event generation time so that we could in a consecutive event handler invocation check the time difference between these two events and decide, whether it's a two-button event or not. Phew. But it looks like a kludge. Thanks in advance.

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