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  • Why aren't arrays expandable?

    - by Mustafa
    When we create an array, we cannot change its size; it's fixed. OK, seems nice, we can create a new bigger array and copy the values one by one and that's little slow. What's the technical background of it?

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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  • simple process rollback question

    - by OckhamsRazor
    hi folks! while revising for an exam, i came across this simple question asking about rollbacks in processes. i understand how rollbacks occur, but i need some validation on my answer. The question: my confusion results from the fact that there is interprocess communication between the processes. does that change anything in terms of where to rollback? my answer would be R13, R23, R32 and R43. any help is greatly appreciated! thanks!

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  • JSF: Avoid nested update calls

    - by dhroove
    I don't know if I am on right track or not still asking this question. I my JSF project I have this tree structure: <p:tree id="resourcesTree" value="#{someBean.root}" var="node" selectionMode="single" styleClass="no-border" selection="#{someBean.selectedNode}" dynamic="true"> <p:ajax listener="#{someBean.onNodeSelect}" update=":centerPanel :tableForm :tabForm" event="select" onstart="statusDialog.show();" oncomplete="statusDialog.hide();" /> <p:treeNode id="resourcesTreeNode" > <h:outputText value="#{node}" id="lblNode" /> </p:treeNode> </p:tree> I have to update this tree after I added something or delete something.. But whenever I update this still its nested update also call I mean to say it also call to update these components ":centerPanel :tableForm :tabForm"... This give me error that :tableForm not found in view because this forms load in my central panel and this tree is in my right panel.. So when I am doing some operation on tree is it not always that :tableForm is in my central panel.. (I mean design is something like this only) So now my question is that can I put some condition or there is any way so that I can specify when to update nested components also and when not.... In nut shell is there any way to update only :resoucesTree is such a way that nested updates are not called so that I can avoid error... Thanks in advance.

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  • How to access a variable in other class?

    - by Christine
    Hi! I've problem regarding GUI with one Menu and one Order Class. I've created a variable to store how many items have been selected in the Menu Class. private int totalSelected; The var totalSelected is live updated. It can be changed anytime depending on actionPerformed() function.(Exp: totalSelected will add up all the selected items) In the Order Class, how can I access to the live update variable totalSelected in order to retrieve the live update value? When I invoke getTotalSelected() function inside the Menu Class, I will only obtain a 0 value. Thanks for your help ^^! Please allow me to specify my question clearer. public class MenuTab extends JPanel { private JLabel display; private int totalSelected; public MenuTab() { .... } } public getTotalSelected(){ return totalSelected; } private class SelectedListener implements ActionListener { public void actionPerformed() { ....... //Assume that totalSelected has been updated! display = new JLabel("Total: " + totalSelected); // OK to display totalSelected live value here. } } // A new class is the confirmation of order public class OrderConfirmedTab extends JPanel{ private JLabel displayTotal; private MenuTab order = new MenuTab(); public OrderConfirmedTab() { ...... int totalSelected = order.getTotalSelected(); displayTotal = new JLabel("Total: " + totalSelected); // Problem to display totalSelected live value here. // Will obtain 0; // How can I obtain the live updated value from class MenuTab? Thanks! } }

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  • Ubuntu terminal questions

    - by Camran
    I am wondering about my VPS providers ubuntu terminal. Are all these terminals the same? I think they are so user-UN-friendly. I can't copy-paste into the terminal, when I try opening textfiles, I can't scroll up and down easily. I cant save easily. Nothing is easy... Is it always like this with Ubuntu? Is there any way to make it easier? I use windows but I login to my vps provider with login details and then simply click "terminal" to open the terminal. Please help me out here

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  • Struts2 Converting Enum Array fills array with single null value

    - by Kyle Partridge
    For a simple action class with these member variables: ... private TestConverterEnum test; private TestConverterEnum[] tests; private List<TestConverterEnum> tList; ... And a simple enum: public enum TestConverterEnum { A, B, C; } Using the default struts2 enum conversion, when I send the request like so: TestConterter.action?test=&tests=&tList=&b=asdf For test I get a null value, which is expected. For the Array and List, however, I get and Array (or list) with one null element. Is this what is expected? Is there a way to prevent this. We recently upgraded our struts2 version, and we had our own converters, which also don't work in this case, so I was hoping to use the default conversion method. We already have code that is validating these arrays for null and length, and I don't want to have to add another condition to these branches. Is there a way to prevent this bevavior?

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  • KeyStore, HttpClient, and HTTPS: Can someone explain this code to me?

    - by stormin986
    I'm trying to understand what's going on in this code. KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); FileInputStream instream = new FileInputStream(new File("my.keystore")); try { trustStore.load(instream, "nopassword".toCharArray()); } finally { instream.close(); } SSLSocketFactory socketFactory = new SSLSocketFactory(trustStore); Scheme sch = new Scheme("https", socketFactory, 443); httpclient.getConnectionManager().getSchemeRegistry().register(sch); My Questions: trustStore.load(instream, "nopassword".toCharArray()); is doing what exactly? From reading the documentation load() will load KeyStore data from an input stream (which is just an empty file we just created), using some arbitrary "nopassword". Why not just load it with null as the InputStream parameter and an empty string as the password field? And then what is happening when this empty KeyStore is being passed to the SSLSocketFactory constructor? What's the result of such an operation? Or -- is this simply an example where in a real application you would have to actually put a reference to an existing keystore file / password?

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  • Best way to implement refusing a value change by the user in Swing?

    - by Michael Borgwardt
    I have a JCheckBox that should not be checked by the user when a certain other field is empty. So now I want to have an error popup and then reset the checkbox (I've considered disabling the checkbox, but the connection to the other field is non-obvious, and a tooltip text IMO not visible enough). What's the correct way to do that in Swing? Through a PropertyVetoException? Where do I throw it and where do I catch it? My first (probably ugly) idea would be to add a ChangeListener that itself shows the popup and resets the value.

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  • How to effectively color pixels in a BufferedImage?

    - by Ed Taylor
    I'm using the following pice of code to iterate over all pixels in an image and draw a red 1x1 square over the pixels that are within a certain RGB-tolerance. I guess there is a more efficient way to do this? Any ideas appreciated. (bi is a BufferedImage and g2 is a Graphics2D with its color set to Color.RED). Color targetColor = new Color(selectedRGB); for (int x = 0; x < bi.getWidth(); x++) { for (int y = 0; y < bi.getHeight(); y++) { Color pixelColor = new Color(bi.getRGB(x, y)); if (withinTolerance(pixelColor, targetColor)) { g2.drawRect(x, y, 1, 1); } } } private boolean withinTolerance(Color pixelColor, Color targetColor) { int pixelRed = pixelColor.getRed(); int pixelGreen = pixelColor.getGreen(); int pixelBlue = pixelColor.getBlue(); int targetRed = targetColor.getRed(); int targetGreen = targetColor.getGreen(); int targetBlue = targetColor.getBlue(); return (((pixelRed >= targetRed - tolRed) && (pixelRed <= targetRed + tolRed)) && ((pixelGreen >= targetGreen - tolGreen) && (pixelGreen <= targetGreen + tolGreen)) && ((pixelBlue >= targetBlue - tolBlue) && (pixelBlue <= targetBlue + tolBlue))); }

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  • Meta Search Engine Architecture

    - by Loki
    The question wasn't clear enough, I think; here's an updated straight to the point question: What are the common architectures used in building a meta search engine and is there any libraries available to build that type of search engine? I'm looking at building an "enterprise" type of search engine where the indexed data could be coming from proprietary (like Autonomy or a Google Box) or public search engines (like Google Web or Yahoo Web).

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  • Removing HTML entities while preserving line breaks with JSoup

    - by shrodes
    I have been using JSoup to parse lyrics and it has been great until now, but have run into a problem. I can use Node.html() to return the full HTML of the desired node, which retains line breaks as such: Gl&oacute;andi augu, silfurn&aacute;tt <br />Bl&oacute;&eth; alv&ouml;ru, starir &aacute; <br />&Oacute;&eth;ur hundur er &iacute; v&iacute;gam&oacute;&eth;, &iacute; maga... m&eacute;r <br /> <br />Kolni&eth;ur gref, kvik sem dreg h&eacute;r <br />Kolni&eth;ur svart, hvergi bjart n&eacute; But has the unfortunate side-effect, as you can see, of retaining HTML entities and tags. However, if I use Node.text(), I can get a better looking result, free of tags and entities: Glóandi augu, silfurnátt Blóð alvöru, starir á Óður hundur er í vígamóð, í maga... mér Kolniður gref, kvik sem dreg hér Kolniður svart, Which has another unfortunate side-effect of removing the line breaks and compressing into a single line. Simply replacing <br /> from the node before calling Node.text() yields the same result, and it seems that that method is compressing the text onto a single line in the method itself, ignoring newlines. Is it possible to have the best of both worlds, and have tags and entities replaced correctly which preserving the line breaks, or is there another method or way of decoding entities and removing tags without having to replace them manually?

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  • How to set the transaction isolation level of a

    - by Michael Wiles
    How do I set the global transaction isolation level for a postgres data source. I'm running on jboss and I'm using hibernate to connect. I know that I can set the isolation level from hibernate, does this work for Postgres? This would be by setting the hibernate.connection.isolation hibernate property to 1,2,4,8 - the various values of the relevant static fields. I'm using the org.postgresql.xa.PGXADataSource

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  • A simple two column layout with Swing

    - by Derk
    How to get a sidebar JPanel of a fixed with with Swing. Now I'm trying this: public SidebarPanel() { this.setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS)); this.setPreferredSize(new Dimension(200, this.getPreferredSize().height)); ... But when I resize the window also the width of the sidebar changes. How to fix this?

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  • how to know which special character is there in a file?

    - by Pangea
    My app needs to process text files during a batch process. Occassionally I receive a file with some special character at the end of the file. I am not sure what that special character is. Is there anyway I can find what that character is so that I can tell the other team which is producing that file. I have used mozilla's library to guess the file encoding and it says UTF-8.

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  • Get interface constant name using its value

    - by Ravisha
    This might not have a major usecase in projects ,but i was just trying a POC kind of project where in i get the key code,and using its value i want to print the key name on screen so i want to relive myself off writing switch cases ,so thinking of going by reflection. Is there a way to get the constant integer of interface's name using its value?

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  • Jpa subclass mapping

    - by Roy Chan
    I am making a POS like system. I wonder how to map subclass using JPA (this is for my DAO). Product class has product details and OrderProduct class has information about the Product and details about the order. @Entity @Table(name="products") public class Product implements Serializable{ @Id @Column(name="id") @GeneratedValue(strategy = GenerationType.AUTO public int getId(){ return id;} /** Other get/set methods */ } @Entity @Table(name="order_products") public class OrderProduct extends Product{ @Id @Column(name="id") @GeneratedValue(strategy = GenerationType.AUTO) public int getId(){ return id;} /** Other get/set methods */ } I got complain about duplicate @Id. But OrderProduct class really need another id than the product one. How should I map this? DB is something like this Table products id int name varchar(32) Table order_product id int quantity int productid int fk referencing product table Would @IdClass or @AttributeOverride help?

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  • Files written with FileWriter are either 32 KB, 24 KB, 16 KB, ... big or empty

    - by Bernhard V
    Hi, I read a file into a string, change the first line and then write this string into a new file. I do this through the following code (a little bit shortened): while(jspIterator.hasNext()){ String line = (String) jspIterator.next(); if (i == 0) { if (line.startsWith("bla bla") && line.endsWith("yada")) { line = line.replaceFirst("this", "that"); } } jspAsString += line; i++; } FileWriter newJspWriter = new FileWriter(newJspFile); newJspWriter.write(jspAsString); Now the files written this way are either 32, 24, 16, 8 KByte big or completely empty. When debugging I see that the String is assembled correctly. When I print the variable jspAsString to the console it also appears correct. Do you know why FileWriter behaves this way?

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  • Catch FileNotFoundException in AsyncTask method

    - by Musterknabe
    I'm getting the favicon of a website with a method. Of course not every website has a favicon. So I want to catch it. The app doesn't crash if the website doesn't have a favicon but I still get an FileNotFoundException in the LogCat. The problem I'm encountering is that I can't catch it When I add `catch (FileNotFoundException f) to my try-catch block it tells me Unreachable catch block for FileNotFoundException. This exception is never thrown from the try statement body. The options I have is to remove it or to add a throws declaration to the doInBackground-method. The latter is not possible. This is the whole Try-Catch try{ String baseURL = getBaseURL ( sourceURLArr[i] ); System.out.println(baseURL + "/favicon.ico"); Bitmap favicon = getBitmapFromURL( baseURL + "/favicon.ico"); Drawable fv = new BitmapDrawable(getResources(), Bitmap.createScaledBitmap(favicon, 20, 20, true)); source [i].setCompoundDrawablesWithIntrinsicBounds(fv, null, null, null); } catch(NullPointerException e){ } catch(FileNotFoundException f){ } I already tried to switch the FileNotFoundException with the NullPointerException but it was the same error. When I add the throws to the asynctask do in background method I get Exception FileNotFoundException is not compatible with throws clause in AsyncTask<Void,Void,Void>.doInBackground(Void[]) How can I now catch the FileNotFoundException?

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  • Is it valid for Hibernate list() to return duplicates?

    - by skaffman
    Is anyone aware of the validity of Hibernate's Criteria.list() and Query.list() methods returning multiple occurrences of the same entity? Occasionally I find when using the Criteria API, that changing the default fetch strategy in my class mapping definition (from "select" to "join") can sometimes affect how many references to the same entity can appear in the resulting output of list(), and I'm unsure whether to treat this as a bug or not. The javadoc does not define it, it simply says "The list of matched query results." (thanks guys). If this is expected and normal behaviour, then I can de-dup the list myself, that's not a problem, but if it's a bug, then I would prefer to avoid it, rather than de-dup the results and try to ignore it. Anyone got any experience of this?

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  • What can cause my code to run slower when the server JIT is activated?

    - by durandai
    I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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