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  • Object Slicing, Is it advantage ?

    - by harigm
    Object slicing is some thing that object looses some of its attributes or functions when a child class is assigned to base class. Some thing like Class A{ } Class B extends A{ } Class SomeClass{ A a = new A(); B b = new B(); // Some where if might happen like this */ a = b; (Object slicing happens) } Do we say Object slicing is any beneficial in any ways? If yes, can any one please tell me how object slicing be a helpful in development and where it might be helpful?

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  • With the introduction of the HTML5 <canvas> element, could Swing be implemented in GWT?

    - by knorv
    With the introduction of the HTML5 <canvas> element, could Swing theoretically be implemented in Google Web Toolkit (GWT) by using the <canvas> tag for drawing? I'm aware of efforts to port source code from using Swing calls to GWT calls, but what I'm after is a pure behind the scenes port where a Swing application would compile under GWT without any source code modifications. Is that theoretically possible? Why? Why not?

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  • Difference between null==object and object==null

    - by priyank.mp
    Hi I would like to know diff between the above comparisons? I am getting null pointer exception when I check object.getItems() == null. But if I change it to null == object.getItems(), it workes fine. I did look into this http://stackoverflow.com/questions/2938476/what-is-the-difference-between-null-object-and-objectnull-closed But I didnt get satisfactory answer.

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  • HyperJAXB and IDREFs

    - by finrod
    I have eventually managed to fiddle HyperJAXB so that when XSD has complexType A and this has an IDREF to complexType B, then HyperJAXB will generate @OneToOne JPA annotations between the the two generated entities. However now I'm facing another problem: the XSD has complex type X that can IDREF to either complex type Y or complex type Z. In the end, I need instance of complex type X contain reference to either instance of class Y or class Z. Do you have any wild ideas how can this be done without manual alterations to the generated classes? And at the same time to make sure these entities are marshalled to a correct XML? How about using the JAXB plugin that allows generating classes so that they implement a particular interface? Could that lead anywhere?

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  • how can I convert String to SecretKey

    - by Alaa
    I want to convert String to secretKey public void generateCode(String keyStr){ KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(128); // 192 and 256 bits may not be available // Generate the secret key specs. secretKey skey=keyStr; //How can I make the casting here //SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); } I try to use BASE64Decoder instead of secretKey, but I face a porblem which is I cannot specify key length. EDIT: I want to call this function from another place static public String encrypt(String message , String key , int keyLength) throws Exception { // Get the KeyGenerator KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(keyLength); // 192 and 256 bits may not be available // Generate the secret key specs. //decode the BASE64 coded message SecretKey skey = key; //here is the error raw = skey.getEncoded(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); // Instantiate the cipher Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); System.out.println("msg is" + message + "\n raw is" + raw); byte[] encrypted = cipher.doFinal(message.getBytes()); String cryptedValue = new String(encrypted); System.out.println("encrypted string: " + cryptedValue); return cryptedValue; } Any one can help, i'll be very thankful.

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  • Accessing the feed/entry/id field of an ATOM 1.0 feed with the ROME library

    - by PartlyCloudy
    Hi, I feel a bit stupid asking this question, but I don't know how I can access the ID field of an entry when using ROME to parse an Atom feed. ROME provides it's own meta level of feeds/items, i.e. SyndFeed and SyndEntry. Being an abstraction over RSS and ATOM they only contain elements both formats support. Thus, there is no method to get an ID of an entry. There also exist low level packages for the distinct formats, and the Atom package contains com.sun.syndication.feed.atom.Entry, which provides getId(). However, I don't know how can I convert my SyndEntry into an Entry. I have not found a way to convert it. The (outdated) tutorials show a conversion, but that's only for output though. So how can I easily access the ID field? Thanks in advance.

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  • controlling threads flow

    - by owca
    I had a task to write simple game simulating two players picking up 1-3 matches one after another until the pile is gone. I managed to do it for computer choosing random value of matches but now I'd like to go further and allow humans to play the game. Here's what I already have : http://paste.pocoo.org/show/201761/ Class Player is a computer player, and PlayerMan should be human being. Problem is, that thread of PlayerMan should wait until proper value of matches is given but I cannot make it work this way. Logic is as follows: thread runs until matches equals to zero. If player number is correct at the moment function pickMatches() is called. After decreasing number of matches on table, thread should wait and another thread should be notified. I know I must use wait() and notify() but I can't place them right. Class Shared keeps the value of current player, and also amount of matches. public void suspendThread() { suspended = true; } public void resumeThread() { suspended = false; } @Override public void run(){ int matches=1; int which = 0; int tmp=0; Shared data = this.selectData(); String name = this.returnName(); int number = this.getNumber(); while(data.getMatches() != 0){ while(!suspended){ try{ which = data.getCurrent(); if(number == which){ matches = pickMatches(); tmp = data.getMatches() - matches; data.setMatches(tmp, number); if(data.getMatches() == 0){ System.out.println(" "+ name+" takes "+matches+" matches."); System.out.println("Winner is player: "+name); stop(); } System.out.println(" "+ name+" takes "+matches+" matches."); if(number != 0){ data.setCurrent(0); } else{ data.setCurrent(1); } } this.suspendThread(); notifyAll(); wait(); }catch(InterruptedException exc) {} } } } @Override synchronized public int pickMatches(){ Scanner scanner = new Scanner(System.in); int n = 0; Shared data = this.selectData(); System.out.println("Choose amount of matches (from 1 to 3): "); if(data.getMatches() == 1){ System.out.println("There's only 1 match left !"); while(n != 1){ n = scanner.nextInt(); } } else{ do{ n = scanner.nextInt(); } while(n <= 1 && n >= 3); } return n; } }

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  • Mismatched coordinate systems in LWJGL with Mouse and Textures

    - by Braains
    I'm not really sure how to expand on this other than to say that it appears that my LWJGL seems to have different coordinate systems for the Mouse and for painting Textures. It seems that Textures have the usual Java2D way of putting (0, 0) in the upper-left corner, while the Mouse goes by the more sensible way of having the origin in the lower-left corner. I've checked my code a bunch but I don't see anything modifying the values between where I read them and where I use them. It's thrown me for a loop and I can't quite figure it out. I'll post all the code that involves the Mouse input and Texture painting for you guys to look at. private static void pollHelpers() { while(Mouse.next()) { InputHelper.acceptMouseInput(Mouse.getEventButton(), Mouse.getEventX(), Mouse.getEventY()); } while (Keyboard.next()) { if (Keyboard.getEventKeyState()) { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), true); } else { InputHelper.acceptKeyboardInput(Keyboard.getEventKey(), false); } } } public static void acceptMouseInput(int mouseButton, int x, int y) { for(InputHelper ie: InputHelper.instances) { if(ie.checkRectangle(x, y)) { ie.sendMouseInputToParent(mouseButton); } } } private void sendMouseInputToParent(int mouseButton) { parent.onClick(mouseButton); } public boolean checkRectangle(int x, int y) { //y = InputManager.HEIGHT - y; See below for explanation return x > parent.getX() && x < parent.getX() + parent.getWidth() && y > parent.getY() && y < parent.getY() + parent.getHeight(); } I put this line of code in because it temporarily fixed the coordinate system problem. However, I want to have my code to be as independent as possible so I want to remove as much reliance on other classes as possible. These are the only methods that touch the Mouse input, and as far as I can tell none of them change anything so all is good here. Now for the Texture methods: public void draw() { if(!clicked || deactivatedImage == null) { activatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(activatedImage, x, y, width, height); } glEnd(); } else { deactivatedImage.bind(); glBegin(GL_QUADS); { DrawHelper.drawGLQuad(deactivatedImage, x, y, width, height); } glEnd(); } } public static void drawGLQuad(Texture texture, float x, float y, float width, float height) { glTexCoord2f(x, y); glVertex2f(x, y); glTexCoord2f(x, y + texture.getHeight()); glVertex2f(x, y + height); glTexCoord2f(x + texture.getWidth(), y + texture.getHeight()); glVertex2f(x + width, y +height); glTexCoord2f(x + texture.getWidth(), y); glVertex2f(x + width, y); } I'll be honest, I do not have the faintest clue as to what is really happening in this method but I was able to put it together on my own and get it to work. my guess is that this is where the problem is. Thanks for any help!

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  • Using progress bar in file search

    - by i2ijeya
    I am writing an application which will search for a particular file or files from the respective path. During searching i need to deploy a progress bar which must run according to the search. so how i can do that? and if possible please post the code?

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  • How to simply this logic/code?

    - by Tattat
    I want to write an apps that accepts user command. The user command is used in this format: command -parameter For example, the app can have "Copy", "Paste", "Delete" command I am thinking the program should work like this : public static void main(String args[]){ if(args[0].equalsIgnoreCase("COPY")){ //handle the copy command } else if(args[0].equalsIgnoreCase("PASTE")){ //handle the copy command }/** code skipped **/ } So, it works, but I think it will become more and more complex when I have more command in my program, also, it is different to read. Any ideas to simply the logic?

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  • unable to add objects to saved collection in GAE using JDO

    - by Jeffrey Chee
    I have a ClassA containing an ArrayList of another ClassB I can save a new instance of ClassA with ClassB instances also saved using JDO. However, When I retrieve the instance of Class A, I try to do like the below: ClassA instance = PMF.get().getPersistenceManager().GetObjectByID( someid ); instance.GetClassBArrayList().add( new ClassB(...) ); I get an Exception like the below: Uncaught exception from servlet com.google.appengine.api.datastore.DatastoreNeedIndexException: no matching index found.. So I was wondering, Is it possible to add a new item to the previously saved collection? Or was it something I missed out. Best Regards

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  • Adding an HTTP Header to the request in a servlet filter

    - by Mason
    I'm integrating with an existing servlet that pulls some properties out of the HTTP header. Basically, I'm implementing an interface that doesn't have access to the actual request, it just has access to a map of k-v for the HTTP headers. I need to pass in a request parameter. The plan is to use a servlet filter to go from parameter to header value but of course the HttpServletRequest object doesn't have an addHeader() method. Any ideas?

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  • Application lifecycle and onCreate method in the the android sdk

    - by Leif Andersen
    I slapped together a simple test application that has a button, and makes a noise when the user clicks on it. Here are it's method: @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Button b = (Button)findViewById(R.id.easy); b.setOnClickListener(this); } public void onClick(View v) { MediaPlayer mp = MediaPlayer.create(this, R.raw.easy); mp.start(); while(true) { if (!mp.isPlaying()) { mp.release(); break; } } } My question is, why is onCreate acting like it's in a while loop? I can click on the button whenever, and it makes the sound. I might think it was just a property of listeners, but the Button object wasn't a member variable. I thought that Android would just go through onCreate onse, and proceed onto the next lifecycle method. Also, I know that my current way of seeing if the sound is playing is crap...I'll get to that later. :) Thank you.

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  • autocommit and @Transactional and Cascading with spring, jpa and hibernate

    - by subes
    Hi, what I would like to accomplish is the following: have autocommit enabled so per default all queries get commited if there is a @Transactional on a method, it overrides the autocommit and encloses all queries into a single transaction, thus overriding the autocommit if there is a @Transactional method that calls other @Transactional annotated methods, the outer most annotation should override the inner annotaions and create a larger transaction, thus annotations also override eachother I am currently still learning about spring-orm and couldn't find documentation about this and don't have a test project for this yet. So my questions are: What is the default behaviour of transactions in spring? If the default differs from my requirement, is there a way to configure my desired behaviour? Or is there a totally different best practice for transactions? --EDIT-- I have the following test-setup: @javax.persistence.Entity public class Entity { @Id @GeneratedValue private Integer id; private String name; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } @Repository public class Dao { @PersistenceContext private EntityManager em; public void insert(Entity ent) { em.persist(ent); } @SuppressWarnings("unchecked") public List<Entity> selectAll() { List<Entity> ents = em.createQuery("select e from " + Entity.class.getName() + " e").getResultList(); return ents; } } If I have it like this, even with autocommit enabled in hibernate, the insert method does nothing. I have to add @Transactional to the insert or the method calling insert for it to work... Is there a way to make @Transactional completely optional?

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  • Working with Hibernate Queries

    - by jschoen
    I am new to hibernate queries, and trying to get a grasp on how everything works. I am using Hibernate 3 with Netbeans 6.5. I have a basic project set up and have been playing around with how to do everything. I started with essentially a search query. Where the user can enter values into one or more fields. The table would be Person with the columns first_name, middle_name, last_name for the sake of the example. The first way I found was to have a method that took firstName, middleName, and lastName as parameters: Session session = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = session.beginTransaction(); String query = "from Person where (first_name = :firstName or :firstName is null) "+ "and (middle_name = :middleName or :middleName is null) " "and (last_name = :lastname or :lastName is null)"; Query q = session.createQuery(query); q.setString("firstName", firstName); q.setString("middleName", middleName); q.setString("lastName", lastName); List<Person> results = (List<Person>) q.list(); This did not sit well with me, since it seemed like I should not have to write that much, and well, that I was doing it wrong. So I kept digging and found another way: Session session = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = session.beginTransaction(); Criteria crit = session.createCriteria(Person.class); if (firstName != null) { crit.add(Expression.ge("firstName", firstName); } if (middleName != null) { crit.add(Expression.ge("middleName", middleName); } if (lastName != null) { crit.add(Expression.ge("lastName", lastName); } List<Person> results = (List<Person>) crit.list(); So what I am trying to figure out is which way is the preferred way for this type of query? Criteria or Query? Why? I am guessing that Criteria is the preferred way and you should only use Query when you need to write it by hand for performance type reasons. Am I close?

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  • Jasper exported to Excel ignoring background color?

    - by discgolfer
    Have you ever had alternating background colors in a Jasper report and then exported it to Excel? The Excel export seems to ignore the alternating color. I've got a Jasper report where the rows alternating background color using the procedure referenced HERE. When I preview it using the viewer or export to PDF it works -- but not when I export to Excel. I've tried using JRXlsExporter and JExcelApiExporter both to no avail. I think it might be a side-effect of how you have to make alternating row colors in Jasper, which I despise to begin with, but have found no other way. Thanks in advance!

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  • Creating queries using Criteria API (JPA 2.0)

    - by Pym
    Hello there ! I'm trying to create a query with the Criteria API from JPA 2.0, but I can't make it work. The problem is with the "between" conditionnal method. I read some documentation to know how I have to do it, but since I'm discovering JPA, I don't understand why it does not work. First, I can't see "creationDate" which should appear when I write "Transaction_." I thought it was maybe normal, since I read the metamodel was generated at runtime, so I tried to use 'Foo_.getDeclaredSingularAttribute("value")' instead of 'Foo_.value', but it still doesn't work at all. Here is my code : public List<Transaction> getTransactions(Date startDate, Date endDate) { EntityManager em = getEntityManager(); try { CriteriaBuilder cb = em.getCriteriaBuilder(); CriteriaQuery<Transaction> cq = cb.createQuery(Transaction.class); Metamodel m = em.getMetamodel(); EntityType<Transaction> Transaction_ = m.entity(Transaction.class); Root<Transaction> transaction = cq.from(Transaction.class); // Error here. cannot find symbol. symbol: variable creationDate cq.where(cb.between(transaction.get(Transaction_.creationDate), startDate, endDate)); // I also tried this: // cq.where(cb.between(Transaction_.getDeclaredSingularAttribute("creationDate"), startDate, endDate)); List<Transaction> result = em.createQuery(cq).getResultList(); return result; } finally { em.close(); } } Can someone help me to figure this out? Thanks.

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  • Variable 'app' in url-pattern for servlet mapping

    - by Brian
    I'm learning Spring MVC (and servlets in general) and following springsource's mvc-ajax example, which uses annotated controller methods. It appears that there is only one url-pattern (in web.xml) mapped to a servlet in that example: /app/* I've deployed the app as a WAR file, and the actual, ugly URL I'm requesting is http://127.0.0.1:8080/org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1/account. So, it appears that 'app' in '/app/*' is a variable corresponding to 'org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1', however, it isn't universal because it isn't usable in my own app, and it contradicts my understanding that url-pattern contains the portion of the URL after the app name. So, what is 'app'? Where is it configured?

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  • JavaFX: Update of ListView if an element of ObservableList changes

    - by user1828169
    I would like to display a list of persons (coded in POJOS, and containing a name and surname property) using a JavaFX ListView control. I created the ListView and added the list of persons as an ObservableList. Everything works fine if I delete or add a new person to the ObservableList, but changes in the POJO do not trigger an update of the ListView. I have to remove and add the modified POJO from the ObservableList to trigger the update of the ListView. Is there any possibility to display changes in POJOS without the workaround described above?

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  • Maven archetype for basic spring hibernate struts2 application

    - by Shekhar
    Hello I am looking for a basic maven archetype which can help me create a spring hibernate struts2 application. I have tried using appfuse but it sucks. It took more than half an hour to download n number of dependencies and the project it created was having errors also. if you know anyother maven archetype please tell me. Thanks Shekhar

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  • Swingworker producing duplicate output/output out of order?

    - by Stefan Kendall
    What is the proper way to guarantee delivery when using a SwingWorker? I'm trying to route data from an InputStream to a JTextArea, and I'm running my SwingWorker with the execute method. I think I'm following the example here, but I'm getting out of order results, duplicates, and general nonsense. Here is my non-working SwingWorker: class InputStreamOutputWorker extends SwingWorker<List<String>,String> { private InputStream is; private JTextArea output; public InputStreamOutputWorker(InputStream is, JTextArea output) { this.is = is; this.output = output; } @Override protected List<String> doInBackground() throws Exception { byte[] data = new byte[4 * 1024]; int len = 0; while ((len = is.read(data)) > 0) { String line = new String(data).trim(); publish(line); } return null; } @Override protected void process( List<String> chunks ) { for( String s : chunks ) { output.append(s + "\n"); } } }

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  • Get children count via HQL

    - by Thomas Lötzer
    Hi, I have a one-to-many mapping between a parent entity and child entities. Now I need to find the number of children associated with each parent for a list of parents. I am trying to do this with HQL but I am not sure how I can get the list of parents in there. Also, I don't know how I can return the entity itself and not just its ID. My current HQL query is: select new map(parent.id as parentId, count(*) as childCount) from Parent parent left join parent.children children group by parent.id but this only returns the ID and does not filter on specific parents. EDIT Based on Pascal's answer I have modified the query to select new map(parent as parent, count(elements(parent.children)) as childCount) from Parent parent group by parent That does work, but is prohibitively slow: 30 seconds instead of 400 ms on the same database.

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  • StringTokenizer split at "<br/>"

    - by AnAmuser
    Maybe I am stupid but I don't understand why the behaviour of StringTokenizer here: import static org.apache.commons.lang.StringEscapeUtils.escapeHtml; String object = (String) value; String escaped = escapeHtml(object); StringTokenizer tokenizer = new StringTokenizer(escaped, escapeHtml("<br/>")); If fx. value is Hej<br/>$user.get(0).name Har vundet<br/><table border='1'><tr><th>Name</th><th>Played</th><th>Brewed</th></tr>#foreach( $u in $user )<tr><td>$u.name</td> <td>$u.played</td> <td>$u.brewed</td></tr>#end</table><br/> Then the result is Hej $use . e (0).name Ha vunde a e o de ='1' h Name h h P ayed h h B ewed h #fo each( $u in $use ) d $u.name d d $u.p ayed d d $u. ewed d #end a e It makes no sense to me. How can I make it behave as I expect to.

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