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  • How SQLite on Android handles long strings?

    - by Levara
    I'm wondering how Android's implementation of SQLite handles long Strings. Reading from online documentation on sqlite, it said that strings in sqlite are limited to 1 million characters. My strings are definitely smaller. I'm creating a simple RSS application, and after parsing a html document, and extracting text, I'm having problem saving it to a database. I have 2 tables in database, feeds and articles. RSS feeds are correctly saved and retrieved from feeds table, but when saving to the articles table, logcat is saying that it cannot save extracted text to it's column. I don't know if other columns are making problems too, no mention of them in logcat. I'm wondering, since text is from an article on web, are signs like (",',;) creating problems? Is Android automaticaly escaping them, or I have to do that. I'm using a technique for inserting similar to one in notepad tutorial: public long insertArticle(long feedid, String title, String link, String description, String h1,tring h2, String h3, String p, String image, long date) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_FEEDID, feedid); initialValues.put(KEY_TITLE, title); initialValues.put(KEY_LINK, link); initialValues.put(KEY_DESCRIPTION, description ); initialValues.put(KEY_H1, h1 ); initialValues.put(KEY_H2, h2); initialValues.put(KEY_H3, h3); initialValues.put(KEY_P, p); initialValues.put(KEY_IMAGE, image); initialValues.put(KEY_DATE, date); return mDb.insert(DATABASE_TABLE_ARTICLES,null, initialValues); } Column P is for extracted text, h1, h2 and h3 are for headers from a page. Logcat reports only column p to be the problem. The table is created with following statement: private static final String DATABASE_CREATE_ARTICLES = "create table articles( _id integer primary key autoincrement, feedid integer, title text, link text not null, description text," + "h1 text, h2 text, h3 text, p text, image text, date integer);";

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  • java number exceeds long.max_value - how to detect?

    - by jurchiks
    I'm having problems detecting if a sum/multiplication of two numbers exceeds the maximum value of a long integer. Example code: long a = 2 * Long.MAX_VALUE; System.out.println("long.max * smth > long.max... or is it? a=" + a); This gives me -2, while I would expect it to throw a NumberFormatException... Is there a simple way of making this work? Because I have some code that does multiplications in nested IF blocks or additions in a loop and I would hate to add more IFs to each IF or inside the loop. Edit: oh well, it seems that this answer from another question is the most appropriate for what I need: http://stackoverflow.com/a/9057367/540394 I don't want to do boxing/unboxing as it adds unnecassary overhead, and this way is very short, which is a huge plus to me. I'll just write two short functions to do these checks and return the min or max long. Edit2: here's the function for limiting a long to its min/max value according to the answer I linked to above: /** * @param a : one of the two numbers added/multiplied * @param b : the other of the two numbers * @param c : the result of the addition/multiplication * @return the minimum or maximum value of a long integer if addition/multiplication of a and b is less than Long.MIN_VALUE or more than Long.MAX_VALUE */ public static long limitLong(long a, long b, long c) { return (((a > 0) && (b > 0) && (c <= 0)) ? Long.MAX_VALUE : (((a < 0) && (b < 0) && (c >= 0)) ? Long.MIN_VALUE : c)); } Tell me if you think this is wrong.

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  • JVM to ignore certificate name mismatch

    - by Heavy Bytes
    I know there were a lot of questions/answers about how to ignore SSL error in the code. On our dev region dev.domain.tld we have configured a app server over SSL. The certificate that is displayed is for somedev.domain.tld. There is no way to change the certificate, it will always be a domain mismatch. So when I deploy a web-service to https://dev.domain.tld and try to connect/call my webservice I get an exception: Caused by: java.security.cert.CertificateException: No name matching dev.domain.tld found And I have the somedev.domain.tld CERT in my trust store. Now, I saw a lot of samples how to change that in the code (using a Trust Manager that accepts all domains), but how do I specify to the JVM to ignore the domain mismatch when connecting to the server? Is there a -Djavax.net.ssl argument or something? Thank you! UPDATE: Or, since I am using Spring-WS, is there a way to set some property in Spring for that? (WebServiceTemplate) UPDATE I guess I'll have to do use something from Spring Security: http://static.springsource.org/spring-ws/sites/1.5/reference/html/security.html

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  • jQuery adding a row to a table with click() handler for tr

    - by Dave
    I'm having an issue with a control I'm building that contains a table where the body is scrollable. The rows have a click() function handler established like: /** * This function is called when the user clicks the mouse on a row in * our scrolling table. */ $('.innerTable tr').click (function (e) { // // Only react to the click if the mouse was clicked in the DIV or // the TD. // if (event.target.nodeName == 'DIV' || event.target.nodeName == 'TD' ) { // // If the user wasn't holding down the control key, then deselect // any previously selected columns. // if (e.ctrlKey == false) { $('.innerTable tr').removeClass ('selected'); } // // Toggle the selected state of the row that was clicked. // $(this).toggleClass ('selected'); } }); There is a button that adds rows to the table like: $('#innerTable > tbody:last').append('<tr>...some information...</tr>'); While the rows ARE added successfully, for some reason, the static rows work with the click handler, but the newly added rows do not. Is there something I'm missing? Thanks in advance!

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  • Firefox add-on development: Register global dynamic custom keyboard shortcuts

    - by dezwart
    I have been tasked with developing a Firefox add-on that is capable of registering global keyboard shortcuts (ones that will work throughout all areas of Firefox) that will open up the side-bar and execute an XMLRPC request based on previously recorded input. The idea here is that there will be many potential XMLRPC requests that the user will want to execute via a keyboard shortcut. Currently, the add-on is capable of handling pre-defined static keyboard shortcuts via the Firefox overlay. What I would like to achieve, is to allow the user to register their own dynamic custom keyboard shortcut. There is an add-on that currently has some of this functionality, called Keyconfig. I'm not keen on having to ask users to install a second add-on to define their own shortcuts. It also seems that using the dynamic keyboard shortcut registration method in Keyconfig would require the user to close all Firefox windows before the dynamic shortcut is made available. What I would like to know is: Is an XPCOM component the best way to register dynamic keyboard shortcuts from within a Firefox add-on? Is there a way to register the keyboard shortcut so that it is immediately available to all Firefox windows, without having to close the windows beforehand?

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  • How to fix Java Image Fetcher error ?

    - by Frank
    My code looks like this : private static JFileChooser fc; if (fc==null) { fc=new JFileChooser(Image_Dir); fc.addChoosableFileFilter(new Image_Filter()); // Add a custom file filter and disable the default (Accept All) file filter. fc.setAcceptAllFileFilterUsed(false); fc.setAccessory(new Image_Preview(fc)); // Add the preview pane. } int returnVal=fc.showDialog(JFileChooser_For_Image.this,"Get Image"); // Show it. After I select an image from the panel, I got the following error message : Exception in thread "Image Fetcher 0" java.lang.UnsatisfiedLinkError: Native Library C:\Program Files (x86)\Java\jre6\bin\jpeg.dll already loaded in another classloader at java.lang.ClassLoader.loadLibrary0(Unknown Source) at java.lang.ClassLoader.loadLibrary(Unknown Source) at java.lang.Runtime.loadLibrary0(Unknown Source) at java.lang.System.loadLibrary(Unknown Source) at sun.security.action.LoadLibraryAction.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at sun.awt.image.JPEGImageDecoder.<clinit>(Unknown Source) at sun.awt.image.InputStreamImageSource.getDecoder(Unknown Source) at sun.awt.image.FileImageSource.getDecoder(Unknown Source) at sun.awt.image.InputStreamImageSource.doFetch(Unknown Source) at sun.awt.image.ImageFetcher.fetchloop(Unknown Source) at sun.awt.image.ImageFetcher.run(Unknown Source) When I run it from an executable Jar file, it works fine, but after I wrapped it into an exe file, I got the above error, why ? How to fix it ?

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  • Linq and returning types

    - by cdotlister
    My GUI is calling a service project that does some linq work, and returns data to my GUI. However, I am battling with the return type of the method. After some reading, I have this as my method: public static IEnumerable GetDetailedAccounts() { IEnumerable accounts = (from a in Db.accounts join i in Db.financial_institution on a.financial_institution.financial_institution_id equals i.financial_institution_id join acct in Db.z_account_type on a.z_account_type.account_type_id equals acct.account_type_id orderby i.name select new {account_id = a.account_id, name = i.name, description = acct.description}); return accounts; } However, my caller is battling a bit. I think I am screwing up the return type, or not handling the caller well, but it's not working as I'd hoped. This is how I am attempting to call the method from my GUI. IEnumerable accounts = Data.AccountService.GetDetailedAccounts(); Console.ForegroundColor = ConsoleColor.Green; Console.WriteLine("Accounts:"); Console.ForegroundColor = ConsoleColor.White; foreach (var acc in accounts) { Console.WriteLine(string.Format("{0:00} {1}", acc.account_id, acc.name + " " + acc.description)); } int accountid = WaitForKey(); However, my foreach, and the acc - isn't working. acc doesn't know about the name, description and id that I setup in the method. Am I at least close to being right?

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  • How to keep Java Frame from waiting?

    - by pypmannetjies
    I am writing a genetic algorithm that approximates an image with a polygon. While going through the different generations, I'd like to output the progress to a JFrame. However, it seems like the JFrame waits until the GA's while loop finishes to display something. I don't believe it's a problem like repainting, since it eventually does display everything once the while loop exits. I want to GUI to update dynamically even when the while loop is running. Here is my code: while (some conditions) { //do some other stuff gui.displayPolygon(best); gui.displayFitness(fitness); gui.setVisible(true); } public void displayPolygon(Polygon poly) { BufferedImage bpoly = ImageProcessor.createImageFromPoly(poly); ImageProcessor.displayImage(bpoly, polyPanel); this.setVisible(true); } public static void displayImage(BufferedImage bimg, JPanel panel) { panel.removeAll(); panel.setBounds(0, 0, bimg.getWidth(), bimg.getHeight()); JImagePanel innerPanel = new JImagePanel(bimg, 25, 25); panel.add(innerPanel); innerPanel.setLocation(25, 25); innerPanel.setVisible(true); panel.setVisible(true); }

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  • -[UITableViewRowData isEqualToString:]: unrecognized selector sent to instance 0x391dce0

    - by tak
    I have a datatable which shows the list of contacts. when I start the application all the data is loaded correctly.But after selecting a contact, I am sometimes getting this exception :- Program received signal: “EXC_BAD_ACCESS”. and sometimes -[UITableViewRowData isEqualToString:]: unrecognized selector sent to instance 0x391dce0 most probably for this code:- - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } ExpenseTrackerAppDelegate *appDelegate = (ExpenseTrackerAppDelegate *)[[UIApplication sharedApplication] delegate]; Person *person = (Person *)[appDelegate.expensivePersonsList objectAtIndex:indexPath.row]; NSString *name = (NSString *)[NSMutableString stringWithFormat:@"%@ %@" ,person.lastName , person.firstName]; cell.textLabel.text = name; //cell.detailTextLabel.text = person.lastName; // Configure the cell. return cell; } If I replace these lines of code NSString *name = (NSString *)[NSMutableString stringWithFormat:@"%@ %@" ,person.lastName , person.firstName]; cell.textLabel.text = name; with this code cell.textLabel.text = person.lastName; then everything works fine? I dont know what exactly happens?

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  • Is there a more elegant way to act on the first and last items in a foreach enumeration than count++

    - by Edward Tanguay
    Is there a more elegant way to act on the first and last items when iterating through a foreach loop than incrementing a separate counter and checking it each time? For instance, the following code outputs: >>> [line1], [line2], [line3], [line4] <<< which requires knowing when you are acting on the first and last item. Is there a more elegant way to do this now in C# 3 / C# 4? It seems like I could use .Last() or .First() or something like that. using System; using System.Collections.Generic; using System.Text; namespace TestForNext29343 { class Program { static void Main(string[] args) { StringBuilder sb = new StringBuilder(); List<string> lines = new List<string> { "line1", "line2", "line3", "line4" }; int index = 0; foreach (var line in lines) { if (index == 0) sb.Append(">>> "); sb.Append("[" + line + "]"); if (index < lines.Count - 1) sb.Append(", "); else sb.Append(" <<<"); index++; } Console.WriteLine(sb.ToString()); Console.ReadLine(); } } }

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  • Multidimensional data structure?

    - by Austin Truong
    I need a multidimensional data structure with a row and a column. Must be able to insert elements any location in the data structure. Example: {A , B} I want to insert C in between A and B. {A, C, B}. Dynamic: I do not know the size of the data structure. Another example: I know the [row][col] of where I want to insert the element. EX. insert("A", 1, 5), where A is the element to be inserted, 1 is the row, 5 is the column. EDIT I want to be able to insert like this. static void Main(string[] args) { Program p = new Program(); List<string> list = new List<string>(); list.Insert(1, "HELLO"); list.Insert(5, "RAWR"); for (int i = 0; i < list.Count; i++) { Console.WriteLine(list[i]); } Console.ReadKey(); } And of course this crashes with an out of bounds error. So in a sense I will have a user who will choose which ROW and COL to insert the element to.

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  • Firefox extension js object initialization

    - by Michael
    Note: this is about Firefox extension, not a js general question. In Firefox extension project I need my javascript object to be initialized just once per Firefox window. Otherwise each time I open my window a new timers will be engaged, new properties will be used, so everything will start from scratch. hope example below will demystify my question :) var StupidExtension { statusBarValue: "Not Initialized Yet", startup: function () { ... // Show statusBarValue in Status Bar Panel }, initTimerToRetrieveStatusBarValueFromNetwork: function () { ... } } so each time you hit Ctrl+N a new window you will see "Not Initialized Yet" and then new timer will be fired, so after some time it retrieve data from network you will see value also on second window and so on. Ideally would be to have just a single timer function running and updating all status bar panels in all Firefox windows. Of course I can do some caching, like saving the value in prefs or some other storage, then show it from there. But I feel like this is artificial. So the question will be is there "native" technique of making static some parts of the object among all Firefox window instances?

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  • Is this the intention behavior in JComboBox? How I can avoid this behavior?

    - by Yan Cheng CHEOK
    I realize that if you are having a same selection in JComboBox, using up/down arrow key, will not help you to navigate the selection around. How I can avoid this behavior? See the below screen shoot /* * To change this template, choose Tools | Templates * and open the template in the editor. */ /* * NewJFrame.java * * Created on May 8, 2010, 7:46:28 PM */ package javaapplication26; /** * * @author yccheok */ public class NewJFrame extends javax.swing.JFrame { /** Creates new form NewJFrame */ public NewJFrame() { initComponents(); /* If you are having 3 same strings here. Using, up/down arrow key, * will not move the selection around. */ this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); this.jComboBox1.addItem("Intel"); } /** This method is called from within the constructor to * initialize the form. * WARNING: Do NOT modify this code. The content of this method is * always regenerated by the Form Editor. */ @SuppressWarnings("unchecked") // <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() { jComboBox1 = new javax.swing.JComboBox(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); jComboBox1.setEditable(true); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(105, 105, 105) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 158, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(137, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(63, 63, 63) .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap(217, Short.MAX_VALUE)) ); pack(); }// </editor-fold> /** * @param args the command line arguments */ public static void main(String args[]) { java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new NewJFrame().setVisible(true); } }); } // Variables declaration - do not modify private javax.swing.JComboBox jComboBox1; // End of variables declaration }

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  • How to extract the Sql Command from a Complied Linq Query

    - by Harry
    In normal (not compiled) Linq to Sql queries you can extract the SQLCommand from the IQueryable via the following code: SqlCommand cmd = (SqlCommand)table.Context.GetCommand(query); Is it possible to do the same for a compiled query? The following code provides me with a delegate to a compiled query: private static readonly Func<Data.DAL.Context, string, IQueryable<Word>> Query_Get = CompiledQuery.Compile<Data.DAL.Context, string, IQueryable<Word>>( (context, name) => from r in context.GetTable<Word>() where r.Name == name select r); When i use this to generate the IQueryable and attempt to extract the SqlCommand it doesn't seem to work. When debugging the code I can see that the SqlCommand returned has the 'very' useful CommandText of 'SELECT NULL AS [EMPTY]' using (var db = new Data.DAL.Context()) { IQueryable<Word> query = Query_Get(db, "word"); SqlCommand cmd = (SqlCommand)db.GetCommand(query); Console.WriteLine(cmd != null ? cmd.CommandText : "Command Not Found"); } I can't find anything in google about this particular scenario, as no doubt it is not a common thing to attempt... So.... Any thoughts?

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  • Groovy as a substitute for Java when using BigDecimal?

    - by geejay
    I have just completed an evaluation of Java, Groovy and Scala. The factors I considered were: readability, precision The factors I would like to know: performance, ease of integration I needed a BigDecimal level of precision. Here are my results: Java void someOp() { BigDecimal del_theta_1 = toDec(6); BigDecimal del_theta_2 = toDec(2); BigDecimal del_theta_m = toDec(0); del_theta_m = abs(del_theta_1.subtract(del_theta_2)) .divide(log(del_theta_1.divide(del_theta_2))); } Groovy void someOp() { def del_theta_1 = 6.0 def del_theta_2 = 2.0 def del_theta_m = 0.0 del_theta_m = Math.abs(del_theta_1 - del_theta_2) / Math.log(del_theta_1 / del_theta_2); } Scala def other(){ var del_theta_1 = toDec(6); var del_theta_2 = toDec(2); var del_theta_m = toDec(0); del_theta_m = ( abs(del_theta_1 - del_theta_2) / log(del_theta_1 / del_theta_2) ) } Note that in Java and Scala I used static imports. Java: Pros: it is Java Cons: no operator overloading (lots o methods), barely readable/codeable Groovy: Pros: default BigDecimal means no visible typing, least surprising BigDecimal support for all operations (division included) Cons: another language to learn Scala: Pros: has operator overloading for BigDecimal Cons: some surprising behaviour with division (fixed with Decimal128), another language to learn

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  • Save Bitmap image in a location in C#

    - by acadia
    Hello, I have this function to store the bmp image in a desired location as shown below My question is, how do I save the image in C:\temp folder by default, instead of opening the filedialog box? I want to specify sd.fileName=picname+".bmp" and store it in c:\temp by default. I tried to specify Thanks for your help in advance. I tried to public static bool SaveDIBAs( string picname, IntPtr bminfo, IntPtr pixdat ) { SaveFileDialog sd = new SaveFileDialog(); sd.FileName = picname; sd.Title = "Save bitmap as..."; sd.Filter = "Bitmap file (*.bmp)|*.bmp|TIFF file (*.tif)|*.tif|JPEG file (*.jpg)|*.jpg|PNG file (*.png)|*.png|GIF file (*.gif)|*.gif|All files (*.*)|*.*"; sd.FilterIndex = 1; if( sd.ShowDialog() != DialogResult.OK ) return false; Guid clsid; if( ! GetCodecClsid( sd.FileName, out clsid ) ) { MessageBox.Show( "Unknown picture format for extension " + Path.GetExtension( sd.FileName ), "Image Codec", MessageBoxButtons.OK, MessageBoxIcon.Information ); return false; } IntPtr img = IntPtr.Zero; int st = GdipCreateBitmapFromGdiDib( bminfo, pixdat, ref img ); if( (st != 0) || (img == IntPtr.Zero) ) return false; st = GdipSaveImageToFile( img, sd.FileName, ref clsid, IntPtr.Zero ); GdipDisposeImage( img ); return st == 0; }

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  • gcc -finline-functions behaviour?

    - by user176168
    I'm using gcc with the -finline-functions optimization for release builds. In order to combat code bloat because I work on an embedded system I want to say don't inline particular functions. The obvious way to do this would be through function attributes ie attribute(noinline). The problem is this doesn't seem to work when I switch on the global -finline-functions optimisation which is part of the -O3 switch. It also has something to do with it being templated as a non templated version of the same function doesn't get inlined which is as expected. Has anybody any idea of how to control inlining when this global switch is on? Here's the code: #include <cstdlib> #include <iostream> using namespace std; class Base { public: template<typename _Type_> static _Type_ fooT( _Type_ x, _Type_ y ) __attribute__ (( noinline )); }; template<typename _Type_> _Type_ Base::fooT( _Type_ x, _Type_ y ) { asm(""); return x + y; } int main(int argc, char *argv[]) { int test = Base::fooT( 1, 2 ); printf( "test = %d\n", test ); system("PAUSE"); return EXIT_SUCCESS; }

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  • Java RMI Proxy issue

    - by Antony Lewis
    i am getting this error : java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call at Main.main(Main.java:39) my abstract and call class both extend remote. call: public class Call extends UnicastRemoteObject implements rmi.engine.Abstract { public Call() throws Exception { super(Store.PORT, new RClient(), new RServer()); } public String getHello() { System.out.println("CONN"); return "HEY"; } } abstract: public interface Abstract extends Remote { String getHello() throws RemoteException; } this is my main: public static void main(String[] args) { if (args.length == 0) { try { System.out.println("We are slave "); InetAddress ip = InetAddress.getLocalHost(); Registry rr = LocateRegistry.getRegistry(ip.getHostAddress(), Store.PORT, new RClient()); Object ss = rr.lookup("FILLER"); System.out.println(ss.getClass().getCanonicalName()); System.out.println(((Call)ss).getHello()); } catch (Exception e) { e.printStackTrace(); } } else { if (args[0].equals("master")) { // Start Master try { RMIServer.start(); } catch (Exception e) { e.printStackTrace(); } } Netbeans says the problem is on line 39 which is System.out.println(((Call)ss).getHello()); the output looks like this: run: We are slave Connecting 10.0.0.212:5225 $Proxy0 java.lang.ClassCastException: $Proxy0 cannot be cast to rmi.engine.Call at Main.main(Main.java:39) BUILD SUCCESSFUL (total time: 1 second) i am running a master in cmd listening on port 5225.

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  • Java conditional compilation: how to prevent code chunks to be compiled?

    - by khachik
    My project requires Java 1.6 for compilation and running. Now I have a requirement to make it working with Java 1.5 (from the marketing side). I want to replace method body (return type and arguments remain the same) to make it compiling with Java 1.5 without errors. Details: I have an utility class called OS which encapsulates all OS-specific things. It has a method public static void openFile(java.io.File file) throws java.io.IOException { // open the file using java.awt.Desktop ... } to open files like with double-click (start Windows command or open Mac OS X command equivalent). Since it cannot be compiled with Java 1.5, I want to exclude it during compilation and replace by another method which calls run32dll for Windows or open for Mac OS X using Runtime.exec. Question: How can I do that? Can annotations help here? Note: I use ant, and I can make two java files OS4J5.java and OS4J6.java which will contain the OS class with the desired code for Java 1.5 and 1.6 and copy one of them to OS.java before compiling (or an ugly way - replace the content of OS.java conditionally depending on java version) but I don't want to do that, if there is another way. Elaborating more: in C I could use ifdef, ifndef, in Python there is no compilation and I could check a feature using hasattr or something else, in Common Lisp I could use #+feature. Is there something similar for Java? Found this post but it doesn't seem to be helpful. Any help is greatly appreciated. kh.

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  • Java abstract visitor - guarantueed to succeed? If so, why?

    - by disown
    I was dealing with hibernate, trying to figure out the run-time class behind proxied instances by using the visitor pattern. I then came up with an AbstractVisitable approach, but I wonder if it will always produce correct results. Consider the following code: interface Visitable { public void accept(Visitor v); } interface Visitor { public void visit(Visitable visitorHost); } abstract class AbstractVisitable implements Visitable { @Override public void accept(Visitor v) { v.visit(this); } } class ConcreteVisitable extends AbstractVisitable { public static void main(String[] args) { final Visitable visitable = new ConcreteVisitable(); final Visitable proxyVisitable = (Visitable) Proxy.newProxyInstance( Thread.currentThread().getContextClassLoader(), new Class<?>[] { Visitable.class }, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { return method.invoke(visitable, args); } }); proxyVisitable.accept(new Visitor() { @Override public void visit(Visitable visitorHost) { System.out.println(visitorHost.getClass()); } }); } } This makes a ConcreteVisitable which inherits the accept method from AbstractVisitable. In c++, I would consider this risky, since this in AbstractVisitable could be referencing to AbstractVisitable::this, and not ConcreteVisitable::this. I was worried that the code under certain circumstances would print class AbstractVisible. Yet the code above outputs class ConcreteVisitable, even though I hid the real type behind a dynamic proxy (the most difficult case I could come up with). Is the abstract visitor approach above guaranteed to work, or are there some pitfalls with this approach? What guarantees are given in Java with respect to the this pointer?

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  • Connect to Facebook with Javascript Client Library using Adobe AIR

    - by Chuck Hriczko
    I'm having an issue connecting to Facebook through the Javascript Client Library in Adobe AIR. It works fine in the browser but in Adobe AIR it seems to not be able to find the Facebook functions. Here is some code I copied from the Facebook website: (Oh and I have the xd_receiver.htm file in the correct path too) <textarea style="width: 1000px; height: 300px;" id="_traceTextBox"> </textarea> <script src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php" type="text/javascript"></script> // var api = FB.Facebook.apiClient; // require user to login api.requireLogin(function(exception){ FB.FBDebug.logLevel=1; FB.FBDebug.dump("Current user id is " + api.get_session().uid); // Get friends list //5-14-09: this code below is broken, correct code follows //api.friends_get(null, function(result){ // Debug.dump(result, 'friendsResult from non-batch execution '); // }); api.friends_get(new Array(), function(result, exception){ FB.FBDebug.dump(result, 'friendsResult from non-batch execution '); }); }); }); //]]> </script>

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  • Manhattan Heuristic function for A-star (A*)

    - by Shawn Mclean
    I found this algorithm here. I have a problem, I cant seem to understand how to set up and pass my heuristic function. static public Path<TNode> AStar<TNode>(TNode start, TNode destination, Func<TNode, TNode, double> distance, Func<TNode, double> estimate) where TNode : IHasNeighbours<TNode> { var closed = new HashSet<TNode>(); var queue = new PriorityQueue<double, Path<TNode>>(); queue.Enqueue(0, new Path<TNode>(start)); while (!queue.IsEmpty) { var path = queue.Dequeue(); if (closed.Contains(path.LastStep)) continue; if (path.LastStep.Equals(destination)) return path; closed.Add(path.LastStep); foreach (TNode n in path.LastStep.Neighbours) { double d = distance(path.LastStep, n); var newPath = path.AddStep(n, d); queue.Enqueue(newPath.TotalCost + estimate(n), newPath); } } return null; } As you can see, it accepts 2 functions, a distance and a estimate function. Using the Manhattan Heuristic Distance function, I need to take 2 parameters. Do I need to modify his source and change it to accepting 2 parameters of TNode so I can pass a Manhattan estimate to it? This means the 4th param will look like this: Func<TNode, TNode, double> estimate) where TNode : IHasNeighbours<TNode> and change the estimate function to: queue.Enqueue(newPath.TotalCost + estimate(n, path.LastStep), newPath); My Manhattan function is: private float manhattanHeuristic(Vector3 newNode, Vector3 end) { return (Math.Abs(newNode.X - end.X) + Math.Abs(newNode.Y - end.Y)); }

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  • Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

    - by GuruC
    We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • Using $this when not in object context--i am using the latest version of php and mysql

    - by user309381
    This is user.php: include("databse.php");//retrieving successfully first name and lastname from databse file into user.php class user { public $first_name; public $last_name; public static function full_name() { if(isset($this->first_name) && isset($this->last_name)) { return $this->first_name . " " . $this->last_name; } else { return ""; } } } ?> Other php file, index.php: <?php include(databse.php); include(user.php); $record = user::find_by_id(1); $object = new user(); $object->id = $record['id']; $object->username = $record['username']; $object->password = $record['password']; $object->first_name = $record['first_name']; $object->last_name = $record['last_name']; // echo $object->full_name(); echo $object->id;// successfully print the id echo $object->username;//success fully print the username echo->$object->full_name();//**ERROR:Using $this when not in object context** ?>

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