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  • switch statemt functioning improperly and giving error when i put break;

    - by nav
    The following is the code i used in a program - over here the month variable is an integer switch(month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; break; case 2: return 28; break; case 4: case 6: case 9: case 11: return 30; break; default: System.out.println("Invalid month."); return 0; } surprisingly, when i use the above switch construct.. it gives an error saying.. code unreachable for statements after each break statement Then i removed all the break statements, and the new code looks like this --- switch(month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: return 31; case 2: return 28; case 4: case 6: case 9: case 11: return 30; default: System.out.println("Invalid month."); return 0; } Now.. after removing the break statements .. the code worked perfectly well.. My question is... in the switch construct.. it is mandatory to use break.. or else the control flow continued.. and all the conditions are tested and executed!! right??? So why in the world is the previous ** syntactically Right** version giving an error.. and the modified syntactically incorrect version running perfectly well.. Any explanation.. anyone!!

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  • How to fire off a asych thread in a web application, and gaurantee only 1 thread fires?

    - by Blankman
    I want to cache a object in memory. Regenerating the object when the cache expires is fairly expensive, so I want to do the following: When the cache is "about" to expire, I want to fire off a asychronous thread that will go and rebuild the object and then reset the cache. One thing I am worry about is multiple threads firing to fetch the object to cache, I only want a single thread doing this, realizing many people will be hitting the website. This might not be the best use case to do this, but I want to know how to do this sort of thing.

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  • Conceptual inheritance implementation

    - by TheSENDER
    Hi there, I'm writing a spatial data structure and I have a doubt about what's the best NODE implementation. According to my design I have an abstract node entity and three classes which inherit from it: EMPTYNODE, FULLNODE, INTERNALNODE. The first one has no particular data. The second one has 1 reference to a generic element. The third one has 2 references to other nodes. I have found several ways to implement this situation (that I have already coded) but I can't decide what's the best. The first solution that I have found is to use a single class Node that potentially performs all the operation in this way: private static class Node { private Elem elem = null; private Node left = null, right = null; public Elem getElem() { assert isFull(); return elem; } public boolean isEmpty() { return elem == null && left == null; } public boolean isFull() { return elem != null; } public boolean isInternal() { return elem == null && left != null; } } The second solution is to write an explicit division by classes where every class offers only its methods. Obviously in this way we are obliged to perform several casts to the node objects. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); } private static class FullNode extends Node{ private ITriangle elem; @Override public boolean isEmpty() { return false; } @Override public final boolean isFull() { return true; } @Override public final boolean isInternal() { return false; } public Elem getElem() { return elem; } } The third one solution is to use the inheritance allowing every classes to offer all the methods, but the object type should by check by "isEmpty()" and similar methods. In case of wrong call we'll throw an exception. private static abstract class Node { public abstract boolean isEmpty(); public abstract boolean isFull(); public abstract boolean isInternal(); public abstract Elem getElem(); } private static class Empty extends Node{ @Override public boolean isEmpty() { return true; } @Override public final boolean isFull() { return false; } @Override public final boolean isInternal() { return false; } @Override public Elem getElem() { throw new AssertionError(); } } What do you think about these three solutions? Which one would you use? Any other ideas? Thanks for your help. Every idea will be appreciated.

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  • Why do I have to explicitly cast sometimes for varargs?

    - by Daniel Lew
    I've got a Class that uses reflection a lot, so I wrote a method to help out: private <T> T callMethod(String methodName, Class[] parameterTypes, Object[] args) { try { Class c = mVar.getClass(); Method m = c.getMethod(methodName, (Class[]) parameterTypes); return (T) m.invoke(mVar, args); } // Insert exception catching here [...] } This worked well for any method that had parameters, however I had to explicitly cast parameterTypes to Class[] in order for this to work for methods with no parameters (e.g., callMethod('funName', null, null);). I've been trying to figure out why this is the case. It seems to me that if parameterTypes, when null, had no concept of what type it is (Class[]), then I'd need to cast it for getMethod(). But if that's the case, why is getMethod() able to tell the difference between null, and (Class[]) null when the method is invoked?

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  • Io exception: There is no process to read data written to a pipe.

    - by Srikanth
    I'm using Hibernate3.2+Websphere6.0+struts1.3.. After deploying ,application works fine. After some idle time ,i will get this type of error repeatedly,am not able to login at all. Im not using any connection pooling. i feel after idle time its not able to connect to the database again..if i restart the server everything works fine for some time...after that same story.. please help me out

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  • using Hibernate to loading 20K products, modifying the entity and updating to db

    - by Blankman
    I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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  • How to export EclipseLink objects to XML

    - by Raven
    Hi, is there an easy approach to store my model, which I use with EclipseLink, in XML files? I want to implement an export functionality in my program and I was wondering if this can be done with eclipselink or with any other framework. Thanks

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  • Given an array of integers [x0 x1 x2], how do you calculate all possible permutations from [0 0 0] t

    - by user319951
    I am writing a program that takes in an ArrayList and I need to calculate all possible permutations starting with a list of zeroes, up to the value in the corresponding input list. Does anyone know how to iteratively calculate these values? For example, given [ 1 2 ] as input, it should find and store the following lists: [0 0], [1 0], [1 1], [1 2], [0 1], [0 2] Thanks!

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  • inter servlet communication

    - by mithun1538
    Hello everyone, I have two servlets: LoginServlet and MailServlet. LoginServlet queries a mysql table using jdbc to get a string(eMail). What I want is to forward this string to MailServlet which in turn will send an email to that e-mail ID sent by LoginServlet. My question is how do I call and send the variable eMail to MailServlet, from LoginServlet? I thought of creating an instance of the MailServlet as : MailServlet servlet = new MailServlet(); And then use the servlet object to call the function doGet() in MailServlet. But I am feeling that there is some error in this as this is not the right way to call a servlet. So how do I call and pass a variable to MailServlet?

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  • How to get JTree expanded?

    - by Dzmitry Zhaleznichenka
    I have a wizard with several screens where user has to fill his/her details for further processing. At the second screen I have a radio group with three radio buttons that enable additional elements. To proceed, user has to choose one of them. When user selects third button, single-selection JTree filled in with data enables and user has to select an option from it. Then user has to press "Next" to get to next screen. The option he\she had selected is stored as a TreePath. So far so good. My problem is the following. If the user wants to come back from the following screen to the screen with a JTree, I want to provide him\her with the JTree expanded to the option that had been selected and to highlight the option. However, whatsoever I try to do for that (any combinations of expandPath, scrollPathToVisible, addSelectionPath, makeVisible) always provides me with a collapsed tree. I try to expand both leaves and nodes. My code looks like this: rbProcessJTree.setSelected(isProcessJTree()); if (null != getSelectedTablePath()){ trTables.addSelectionPath(getSelectedTablePath()); trTables.expandPath(getSelectedTablePath()); trTables.scrollPathToVisible(getSelectedTablePath()); } When setSelected() is called, state change listener is invoked that enables JTree. The model is loaded during the form initialization. Each time I switch between screens, I save the input data from previous screen and dispose it. Then, when I need to open previous screen back, I save data from the following screen, dispose it, load data to this screen and show it. So each time the screen is generating from scratch. Could you please explain, what sequence of operations has to be done to get JTree expanded in a newly created form,with data model loaded and selection path provided?

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  • Text to speech(TTS)-Android

    - by bharathi
    Hi, I am new to this android platform.now I am Working on TTS(Text to Speech).what I am trying to do is that when i enter the text in the Text area it has to be converted to speech,when i click the speak button.can anyone help me out.Thanks in Advance.

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  • Solr; What does this mean?

    - by Camran
    At the end of the README.txt file which is located in the example directory under solr, I find this line: NOTE: This Solr example server references SolrCell jars outside of the server directory with statements in the solrconfig.xml. If you make a copy of this example server and wish to use the ExtractingRequestHandler (SolrCell), you will need to copy the required jars into solr/lib or update the paths to the jars in your solrconfig.xml What does this mean? Do I have to make some adjustment before uploading solr to my server? Also, if you know, what is Solr-nightly:s difference to regular solr? The tutorial states "solr-nightly.zip" but on their download section I cant find it.

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  • Getting class Type information for Elements on a collection

    - by DutrowLLC
    I would like to get gain access to the type of Object held in a Collection. Below is a simplified example of when and why I might want to do this. Is this even possible? List<Address> addressList = new LinkedList<Address>(); Main.addElement(addressList); Class Main{ public void addElement(Object inArgument){ List<Object> argument = (List<Object>)inArgument; argument.add( /* WOULD LIKE TO CREATE A NEW OBJECT OF THE APPROPRIATE TYPE HERE, IN THIS CASE, IT WOULD BE OF TYPE: "Address" */ ); } }

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  • Do "if" statements affect in the time complexity analysis?

    - by FranXh
    According to my analysis, the running time of this algorithm should be N2, because each of the loops goes once through all the elements. I am not sure whether the presence of the if statement changes the time complexity? for(int i=0; i<N; i++){ for(int j=1; j<N; j++){ System.out.println("Yayyyy"); if(i<=j){ System.out.println("Yayyy not"); } } }

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  • JarEntry.getSize() is returning -1 when the jar files is opened as InputStream from URL

    - by Reshma Donthireddy
    I am trying to read file from the JarInputStream and the size of file is returning -1. I am accessing Jar file from the URL as a inputStream. URLConnection con = url.openConnection(); JarInputStream jis = new JarInputStream(con.getInputStream()); JarEntry je = null; while ((je = jis.getNextJarEntry()) != null) { htSizes.put(je.getName(), new Integer((int) je.getSize())); if (je.isDirectory()) { continue; } int size = (int) je.getSize(); // -1 means unknown size. if (size == -1) { size = ((Integer) htSizes.get(je.getName())).intValue(); } byte[] b = new byte[(int) size]; int rb = 0; int chunk = 0; while (((int) size - rb) > 0) { chunk = jis.read(b, rb, (int) size - rb); if (chunk == -1) { break; } rb += chunk; } // add to internal resource hashtable htJarContents.put(je.getName(), baos.toByteArray()); }

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  • how to check the first time user of my App in android?

    - by androidbase Praveen
    hi all, In my App, first it shows a splash screen. after that another activity, then my main activity must be show. this is my design plan. the second activity(i.e before main activity) must be show for the first time user of the app. if he/she closes the app.splash screen will redirect to main activity automatically. how to do this ? Any Idea? i am developing my app for android phones.

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  • What is the effect of final variable declaration in methods?

    - by Finbarr
    Classic example of a simple server: class ThreadPerTaskSocketServer { public static void main(String[] args) throws IOException { ServerSocket socket = new ServerSocket(80); while (true) { final Socket connection = socket.accept(); Runnable task = new Runnable() { public void run() { handleRequest(connection); } }; new Thread(task).start(); } } } Why should the Socket be declared as final? Is it because the new Thread that handles the request could refer back to the socket variable in the method and cause some sort of ConcurrentModificationException?

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