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  • Java performance issue

    - by Colby77
    Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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  • sem-dynamic cdn

    - by dwi kristianto
    i'm developing couple of websites using php (directory script, etc.) and wordpress as cms. i need to improve its performance, by using cdn for static files (css, js, images). the problem is, css and javascript files are generated on the fly. i did that due to yahoo and some expert advice to combine the files into one file. also changing basic color of css files. for the time being, i use couple of small vps but still its not fast enough. i already contact maxcdn and the support guy said that they dont have such kind of services. what i need is: a cdn that will serve the request from user/visitor and there's no file in local disk, the cdn will redirect/fetch it from another domain/server. in vps, it could be done easily using combination of .htaccess and php, but NOT in the cdn. most of cdn only support purely static files. is there any such cdn that will server semi-dynamic files?

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  • How to use SQLErrorCodeSQLExceptionTranslator and DAO class with @Repository in Spring?

    - by GuidoMB
    I'm using Spring 3.0.2 and I have a class called MovieDAO that uses JDBC to handle the db. I have set the @Repository annotations and I want to convert the SQLException to the Spring's DataAccessException I have the following example: @Repository public class JDBCCommentDAO implements CommentDAO { static JDBCCommentDAO instance; ConnectionManager connectionManager; private JDBCCommentDAO() { connectionManager = new ConnectionManager("org.postgresql.Driver", "postgres", "postgres"); } static public synchronized JDBCCommentDAO getInstance() { if (instance == null) instance = new JDBCCommentDAO(); return instance; } @Override public Collection<Comment> getComments(User user) throws DAOException { Collection<Comment> comments = new ArrayList<Comment>(); try { String query = "SELECT * FROM Comments WHERE Comments.userId = ?"; Connection conn = connectionManager.getConnection(); PreparedStatement stmt = conn.prepareStatement(query); stmt = conn.prepareStatement(query); stmt.setInt(1, user.getId()); ResultSet result = stmt.executeQuery(); while (result.next()) { Movie movie = JDBCMovieDAO.getInstance().getLightMovie(result.getInt("movie")); comments.add(new Comment(result.getString("text"), result.getInt("score"), user, result.getDate("date"), movie)); } connectionManager.closeConnection(conn); } catch (SQLException e) { e.printStackTrace(); //CONVERT TO DATAACCESSEXCEPTION } return comments; } } I Don't know how to get the Translator and I don't want to extends any Spring class, because that is why I'm using the @Repository annotation

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  • dynamic row height

    - by Prasanna Venkatesh
    static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@""]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } //cell.backgroundView = [[[CustomCell alloc] init] autorelease]; cell.selectedBackgroundView = [[[CustomCell alloc] init] autorelease]; // At end of function, right before return cell: cell.textLabel.backgroundColor = [UIColor clearColor]; // Configure the cell. UILabel *myLabel1 = [[UILabel alloc] initWithFrame:CGRectMake(-30, 3, 300, 22)]; UILabel *myLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(10, 22, 310, 200)]; UILabel *myLabel3 = [[UILabel alloc] initWithFrame:CGRectMake(0, 170, 300, 20)]; Book *aBook = [appDelegate.books objectAtIndex:indexPath.row]; myLabel1.text=aBook.title; myLabel2.text=aBook.description; myLabel3.text=aBook.pubDate; NSString *desc = aBook.description; if ([desc isEqualToString:nil]) { NSLog(@"nullll lll "); } //myLabel2.textAlignment=UITextAlignmentCenter; myLabel2.numberOfLines=5; myLabel2.textColor=[UIColor blueColor]; myLabel2.lineBreakMode=UILineBreakModeWordWrap; myLabel2.font=[UIFont systemFontOfSize:14]; myLabel3.numberOfLines=1; myLabel1.numberOfLines=1; myLabel1.textColor=[UIColor redColor]; myLabel1.font=[UIFont systemFontOfSize:20]; myLabel1.shadowColor=[UIColor redColor]; myLabel1.backgroundColor=[UIColor grayColor]; [cell.contentView addSubview:myLabel1]; [cell.contentView addSubview:myLabel2]; [cell.contentView addSubview:myLabel3]; hi guys! i have this following code, i want to display this from xml file. now its working but static row height. if the xml file dont have data then it leaves it as blank. so i want to change row height according to the data i provide using the mylabel1,2,3.text

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  • Beginner: Restore previously serialized JFrame-object, how?

    - by elementz
    Hi all. I have managed to serialize my very basic GUI-object containing a JTextArea and a few buttons to a file 'test.ser'. Now, I would like to completely restore the previously saved state from 'test.ser', but seem to have a misconception of how to properly deserialize an objects state. The class MyFrame creates the JFrame and serializes it. Now I tried to deserialize like so: public class Deserialize { static Deserialize ds; MyFrame frame; public static void main(String[] args) { try { ds.deserialize(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void deserialize() throws ClassNotFoundException { try { ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.ser")); frame = (MyFrame) ois.readObject(); ois.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } Maybe somebody could point me into the direction where my misconception is? Thx in advance!

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  • Android 1.5/1.6 issue with style and autogenerated R.java file

    - by Gaks
    I'm having strange issue with R.java file and styles defined in my resources. Here's some code: In res/values/strings.xml: <style parent="android:Theme.Dialog" name="PopupWindowStyle"> <item name="android:windowBackground">@drawable/bg1</item> <item name="android:textColor">@android:color/black</item> </style> In AndroidManifest.xml: <activity android:name=".RegisterScreen" android:icon="@drawable/ico" android:label="@string/applicationName" android:theme="@style/PopupWindowStyle" android:configChanges="locale|touchscreen|keyboard|keyboardHidden|navigation|orientation|fontScale"> </activity> In autogenerated gen/.../R.java: public static final class style { public static final int PopupWindowStyle=0x7f090000; } After some changes in the project, eclipse changed autogenerated value for PopupWindowStyle from 0x7f080000 to 0x7f090000. After that, on Android 1.5, RegisterScreen activity is displayed without PopupWindowStyle style - there is an error displayed in logcat: Skipping entry 0x7f090000 in package table 0 because it is not complex! On Android 1.6 however everything works fine - PopupWindowStyle works like it was before it's integer value has changed. I was testing this issue, by reverting the source code to older revisions. I can confirm, that this problem started occurring after src code commit, which changed two files completely unrelated to this part of code - and an autogenerated R.java file. Any idea what could cause that?

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  • Improving field get and set performance with ASM or Javassist

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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  • help on ejb stateless datagram and message driven beans

    - by Kemmal
    i have a client thats sending a message to the ejbserver using UDP, i want the server(stateless bean) to echo back this message to the client but i cant seem to do this. or can i implement the same logic by using JMS? please help and enlighten. this is just a test, in the end i want a midp to be sending the message to the ejb using datagrams. here is my code. @Stateless public class SessionFacadeBean implements SessionFacadeRemote { public SessionFacadeBean() { } public static void main(String[] args) { DatagramSocket aSocket = null; byte[] buffer = null; try { while(true) { DatagramPacket request = new DatagramPacket(buffer, buffer.length); aSocket.receive(request); DatagramPacket reply = new DatagramPacket(request.getData(), request.getLength(), request.getAddress(), request.getPort()); aSocket.send(reply); } } catch (SocketException e) { System.out.println("Socket: " + e.getMessage()); } catch (IOException e) { System.out.println("IO: " + e.getMessage()); } finally { if(aSocket != null) aSocket.close(); } } } and the client: public static void main(String[] args) { DatagramSocket aSocket = null; try { aSocket = new DatagramSocket(); byte [] m = "Test message!".getBytes(); InetAddress aHost = InetAddress.getByName("localhost"); int serverPort = 6789; DatagramPacket request = new DatagramPacket(m, m.length, aHost, serverPort); aSocket.send(request); byte[] buffer = new byte[1000]; DatagramPacket reply = new DatagramPacket(buffer, buffer.length); aSocket.receive(reply); System.out.println("Reply: " + new String(reply.getData())); } catch (SocketException e) { System.out.println("Socket: " + e.getMessage()); } catch (IOException e) { System.out.println("IO: " + e.getMessage()); } finally { if(aSocket != null) aSocket.close(); } } please help.

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  • Rails' page caching vs. HTTP reverse proxy caches

    - by John Topley
    I've been catching up with the Scaling Rails screencasts. In episode 11 which covers advanced HTTP caching (using reverse proxy caches such as Varnish and Squid etc.), they recommend only considering using a reverse proxy cache once you've already exhausted the possibilities of page, action and fragment caching within your Rails application (as well as memcached etc. but that's not relevant to this question). What I can't quite understand is how using an HTTP reverse proxy cache can provide a performance boost for an application that already uses page caching. To simplify matters, let's assume that I'm talking about a single host here. This is my understanding of how both techniques work (maybe I'm wrong): With page caching the Rails process is hit initially and then generates a static HTML file that is served directly by the Web server for subsequent requests, for as long as the cache for that request is valid. If the cache has expired then Rails is hit again and the static file is regenerated with the updated content ready for the next request With an HTTP reverse proxy cache the Rails process is hit when the proxy needs to determine whether the content is stale or not. This is done using various HTTP headers such as ETag, Last-Modified etc. If the content is fresh then Rails responds to the proxy with an HTTP 304 Not Modified and the proxy serves its cached content to the browser, or even better, responds with its own HTTP 304. If the content is stale then Rails serves the updated content to the proxy which caches it and then serves it to the browser If my understanding is correct, then doesn't page caching result in less hits to the Rails process? There isn't all that back and forth to determine if the content is stale, meaning better performance than reverse proxy caching. Why might you use both techniques in conjunction?

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  • Inner join and outer join options in Entity Framework 4.0

    - by bigb
    I am using EF 4.0 and I need to implement query with one inner join and with N outer joins I started to implement this using different approaches but get into trouble at some point. Here is two examples how I started of doing this using ObjectQuery<'T' and Linq to Entity 1)Using ObjectQuery<'T' I implement flexible outer join but I don't know how to perform inner join with entity Rules in that case (by default Include("Rules") doing outer join, but i need to inner join by Id). public static IEnumerable<Race> GetRace(List<string> includes, DateTime date) { IRepository repository = new Repository(new BEntities()); ObjectQuery<Race> result = (ObjectQuery<Race>)repository.AsQueryable<Race>(); //perform outer joins with related entities if (includes != null) foreach (string include in includes) result = result.Include(include); //here i need inner join insteard of default outer join result = result.Include("Rules"); return result.ToList(); } 2)Using Linq To Entity I need to have kind of outer join(somethin like in GetRace()) where i may pass a List with entities to include) and also i need to perform correct inner join with entity Rules public static IEnumerable<Race> GetRace2(List<string> includes, DateTime date) { IRepository repository = new Repository(new BEntities()); IEnumerable<Race> result = from o in repository.AsQueryable<Race>() from b in o.RaceBetRules select new { o }); //I need here: // 1. to perform the same way inner joins with related entities like with ObjectQuery above //here i getting List<AnonymousType> which i cant cast to //IEnumerable<Race> when i did try to cast like //(IEnumerable<Race>)result.ToList(); i did get error: //Unable to cast object of type //'System.Collections.Generic.List`1[<>f__AnonymousType0`1[BetsTipster.Entity.Tip.Types.Race]]' //to type //'System.Collections.Generic.IEnumerable`1[BetsTipster.Entity.Tip.Types.Race]'. return result.ToList(); } May be someone have some ideas about that.

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  • Django does not load internal .css files

    - by Rubén Jiménez
    I have created a Django project in local which runs without any kind of problem. But, after an annoying and difficult Cherokee + uWSGI installation on Amazon AWS, my project does not show Django .css internal files. http://f.cl.ly/items/2Q2W3I3R0X1n2X3v0q2P/django_error.jpg <-- /Admin/ looks like The image is a screen of my /admin/, which should have a different style, but .css files are not loaded. [pid: 23206|app: 0|req: 19/19] 83.49.10.217 () {56 vars in 1121 bytes} [Sun Apr 15 05:50:24 2012] GET /static/admin/css/base.css = generated 2896 bytes in 6 msecs (HTTP/1.1 404) 1 headers in 51 bytes (1 switches on core 0) [pid: 23206|app: 0|req: 20/20] 83.49.10.217 () {56 vars in 1125 bytes} [Sun Apr 15 05:50:24 2012] GET /static/admin/css/login.css = generated 2899 bytes in 5 msecs (HTTP/1.1 404) 1 headers in 51 bytes (1 switches on core 0) This is a log from Cherokee. I don't understand why it is looking for the .css files in that path. Cherokee should be searching the files in Django original directory so i didn't change .css files in my project. Any advice? Thanks a lot.

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  • serialport error

    - by I__
    i have the following code: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; namespace WindowsFormsApplication1 { public partial class Form1 : Form { public Form1() { InitializeComponent(); } public class ThreadWork { public static void DoWork() { serialPort1.Open(); serialPort1.Write("AT+CMGF=1\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CNMI=2,2\r\n"); //Thread.Sleep(500); serialPort1.Write("AT+CSCA=\"+4790002100\"\r\n"); //Thread.Sleep(500); serialPort1.DataReceived += serialPort1_DataReceived_1; } } private void Form1_Load(object sender, EventArgs e) { ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork); Thread myThread = new Thread(myThreadDelegate); myThread.Start(); } private void serialPort1_DataReceived_1(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { string response = serialPort1.ReadLine(); this.BeginInvoke(new MethodInvoker(() => textBox1.AppendText(response + "\r\n"))); } } } and for all the serialport1 lines i am getting this error: Error 1 An object reference is required for the non-static field, method, or property 'WindowsFormsApplication1.Form1.serialPort1' C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 23 17 WindowsFormsApplication1 what am i doing wrong?

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  • Excel Automation - creating a new worksheet

    - by Andrew Shepherd
    I am attempting what seems like a simple task: using C# to create a new Excel document containing new worksheets. For some reason, I am getting a strange COM error (0x800A03EC) Has anyone managed to get this to work? Does anyone have suggestions as to how to troubleshoot this? I've isolated this into the minimum amount of code: using Microsoft.Office.Interop.Excel; using System.Diagnostics; namespace ExcelAutomation { public static class ExcelTests { public static void CreateWorksheet() { try { var app = new Microsoft.Office.Interop.Excel.Application(); app.Visible = true; var workBooks = app.Workbooks; var newWorkbook = app.Workbooks.Add(XlWBATemplate.xlWBATWorksheet); Worksheet existingWorksheet = (Worksheet)newWorkbook.Sheets[1]; Worksheet workSheet = (Worksheet)newWorkbook.Sheets.Add ( null, // before existingWorksheet, null, // 1, null //XlSheetType.xlWorksheet ); } catch (System.Runtime.InteropServices.COMException ex) { Trace.WriteLine(string.Format("Caught COMException. Message: \"{0}\"", ex.Message)); } } } } The output window now says: Caught COMException. Message: "Exception from HRESULT: 0x800A03EC"

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  • CustomProfile is not saving?

    - by Xaisoft
    I created a class that extends ProfileBase: public class CustomerProfile : ProfileBase { public int CustomerID { get; set; } public string CustomerName { get; set; } public static CustomerProfile GetProfile() { return Create(Membership.GetUser().UserName) as CustomerProfile; } public static CustomerProfile GetProfile(string userName) { return Create(userName) as CustomerProfile; } } If I do: CustomerProfile p = CustomerProfile.GetProfile(); p.CustomerID = 1; p.Save(); The next time I try to access the value for the current user, it is not 1, it is 0, so it appears it is not saving it in the database. In my web.config file I have the following snippet: <profile inherits="PortalBLL.CustomerProfile"> <providers> <add name="CustomerProfile" type="System.Web.Profile.SqlProfileProvider" applicationName="/" connectionStringName="LocalSqlServer"/> </providers> </profile> I tried the following and it worked, I am curious why it doesn't save it using the automatic properties. [SettingsAllowAnonymous(false)] public int CustomerID { get { return (int)base.GetPropertyValue("CustomerID");} set { base.SetPropertyValue("CustomerID",value);} }

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  • Need help coming up with a better HtmlHelper Extension method.

    - by zSysop
    Hi all, I've inherited the following code and i was wondering if i could pick at your brains to see if there's a nicer way to do duplicate this. Heres the html for most of our partial input views <% if (Html.IsInputReadOnly()) { %> <td> Id </td> <td> <%= Html.TextBox( "Id" , (Model == null ? null : Model.Id) , new { @readonly = "readonly", @disabled="disabled" } )%> <% } elseif (Html.IsInputDisplayable() == false) { %> <td></td> <td></td> <% } else { %> <td>Id</td> <td><%= Html.TextBox("Id")%> <%= Html.ValidationMessage("Id", "*")%> </td> <%} %> Here are my entension methods public static bool IsInputReadOnly(this HtmlHelper helper) { string actionName = ActionName(helper); // The Textbox should be read only on all pages except for the lookup page if (actionName.ToUpper().CompareTo("EDIT") == 0) return true; return false; } public static bool IsInputDisplayable(this HtmlHelper helper) { string actionName = ActionName(helper); // The Textbox should be read only on all pages except for the lookup page if (actionName.ToUpper().CompareTo("CREATE") == 0) return true; return false; } Thanks in advance

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  • JTextArea - Highlight Text While Scrolling Up or Down

    - by Sujay
    I'm trying to work with a non-editable JTextArea added to a JScrollPane. I want a line to be highlighted when the user clicks on that specific line. I could implement this part using the following code: public static void initHighlightOption(final JTextArea textArea){ textArea.setFont(new Font("Courier New", Font.PLAIN, 12)); textArea.setEditable(false); final Action selectLine = getAction(textArea, DefaultEditorKit.selectLineAction); textArea.addMouseListener(new MouseAdapter() { @Override public void mouseClicked(MouseEvent e) { if (SwingUtilities.isLeftMouseButton(e) && e.getClickCount() == 1) { selectLine.actionPerformed(null); } }); textArea.setSelectionStart(0); textArea.setSelectionEnd(0); } public static Action getAction(JTextArea textArea, String name) { Action action = null; Action[] actions = textArea.getActions(); for (int i = 0; i < actions.length; i++) { if (name.equals(actions[i].getValue(Action.NAME).toString())) { action = actions[i]; break; } } return action; } What I want to add is that once a line is highlighted and user scrolls up/down using keyboard up/down key, i want the current line to be highlighted. Is this possible by adding a keyListener? I'm stuck on how highlight data while scrolling up. The text area contains data like this: Line1 Line2 Line3 Line4 Line5 (i.e. there might be new lines between two particular lines of data)

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  • Quartz.Net scheduler works locally but not on remote host

    - by Glinkot
    Hi. I have a timed quartz.net job working fine on my dev machine, but once deployed to a remote server it is not triggering. I believe the job is scheduled ok, because if I postback, it tells me the job already exists (I normally check for postback however). The email code definitely works, as the 'button1_click' event sends emails successfully. I understand I have full or medium trust on the remove server. My host says they don't apply restrictions that they know of which would affect it. Any other things I need to do to get it running? using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using Quartz; using Quartz.Impl; using Quartz.Core; using Aspose.Network.Mail; using Aspose.Network; using Aspose.Network.Mime; using System.Text; namespace QuartzTestASP { public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) { ISchedulerFactory schedFact = new StdSchedulerFactory(); IScheduler sched = schedFact.GetScheduler(); JobDetail jobDetail = new JobDetail("testJob2", null, typeof(testJob)); //Trigger trigger = TriggerUtils.MakeMinutelyTrigger(1, 3); Trigger trigger = TriggerUtils.MakeSecondlyTrigger(10, 5); trigger.StartTimeUtc = DateTime.UtcNow; trigger.Name = "TriggertheTest"; sched.Start(); sched.ScheduleJob(jobDetail, trigger); } } protected void Button1_Click1(object sender, EventArgs e) { myutil.sendEmail(); } } class testJob : IStatefulJob { public testJob() { } public void Execute(JobExecutionContext context) { myutil.sendEmail(); } } public static class myutil { public static void sendEmail() { // tested code lives here and works fine when called from elsewhere } } }

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  • How to do cleanup reliably in python?

    - by Cheery
    I have some ctypes bindings, and for each body.New I should call body.Free. The library I'm binding doesn't have allocation routines insulated out from the rest of the code (they can be called about anywhere there), and to use couple of useful features I need to make cyclic references. I think It'd solve if I'd find a reliable way to hook destructor to an object. (weakrefs would help if they'd give me the callback just before the data is dropped. So obviously this code megafails when I put in velocity_func: class Body(object): def __init__(self, mass, inertia): self._body = body.New(mass, inertia) def __del__(self): print '__del__ %r' % self if body: body.Free(self._body) ... def set_velocity_func(self, func): self._body.contents.velocity_func = ctypes_wrapping(func) I also tried to solve it through weakrefs, with those the things seem getting just worse, just only largely more unpredictable. Even if I don't put in the velocity_func, there will appear cycles at least then when I do this: class Toy(object): def __init__(self, body): self.body.owner = self ... def collision(a, b, contacts): whatever(a.body.owner) So how to make sure Structures will get garbage collected, even if they are allocated/freed by the shared library? There's repository if you are interested about more details: http://bitbucket.org/cheery/ctypes-chipmunk/

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  • In C#, are event handler arguments contravariant?

    - by Roger Lipscombe
    If I have a class that raises an event, with (e.g.) FrobbingEventArgs, am I allowed to handle it with a method that takes EventArgs? Here's some code: class Program { static void Main(string[] args) { Frobber frobber = new Frobber(); frobber.Frobbing += FrobberOnFrobbing; frobber.Frob(); } private static void FrobberOnFrobbing(object sender, EventArgs e) { // Do something interesting. Note that the parameter is 'EventArgs'. } } internal class Frobber { public event EventHandler<FrobbingEventArgs> Frobbing; public event EventHandler<FrobbedEventArgs> Frobbed; public void Frob() { OnFrobbing(); // Frob. OnFrobbed(); } private void OnFrobbing() { var handler = Frobbing; if (handler != null) handler(this, new FrobbingEventArgs()); } private void OnFrobbed() { var handler = Frobbed; if (handler != null) handler(this, new FrobbedEventArgs()); } } internal class FrobbedEventArgs : EventArgs { } internal class FrobbingEventArgs : EventArgs { } The reason I ask is that ReSharper seems to have a problem with (what looks like) the equivalent in XAML, and I'm wondering if it's a bug in ReSharper, or a mistake in my understanding of C#.

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  • Why doesn't is operator take in consideration if the explicit operator is overriden when checking ty

    - by Galilyou
    Hey Guys, Consider this code sample: public class Human { public string Value { get; set;} } public class Car { public static explicit operator Human (Car c) { Human h = new Human(); h.Value = "Value from Car"; return h; } } public class Program { public static void Mani() { Car c = new Car(); Human h = (Human)c; Console.WriteLine("h.Value = {0}", h.Value); Console.WriteLine(c is Human); } } Up I provide a possibility of an explicit cast from Car to Human, though Car and Human hierarchically are not related! The above code simply means that "Car is convertible to human" However, if you run the snippet you will find the expression c is Human evaluates to false! I used to believe that the is operator is kinda expensive cause it attempts to do an actual cast that might result in an InvalidCastException. If the operator is trying to cast, then the cast should succeed as there's an operator logic that should perform the cast! What does "is" test? Does test a hierarchical "is-a" relationship? Does test whether a variable type is convertible to a type?

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  • Reducing Time Complexity in Java

    - by Koeneuze
    Right, this is from an older exam which i'm using to prepare my own exam in january. We are given the following method: public static void Oorspronkelijk() { String bs = "Dit is een boodschap aan de wereld"; int max = -1; char let = '*'; for (int i=0;i<bs.length();i++) { int tel = 1; for (int j=i+1;j<bs.length();j++) { if (bs.charAt(j) == bs.charAt(i)) tel++; } if (tel > max) { max = tel; let = bs.charAt(i); } } System.out.println(max + " keer " + let); } The questions are: what is the output? - Since the code is just an algorithm to determine the most occuring character, the output is "6 keer " (6 times space) What is the time complexity of this code? Fairly sure it's O(n²), unless someone thinks otherwise? Can you reduce the time complexity, and if so, how? Well, you can. I've received some help already and managed to get the following code: public static void Nieuw() { String bs = "Dit is een boodschap aan de wereld"; HashMap<Character, Integer> letters = new HashMap<Character, Integer>(); char max = bs.charAt(0); for (int i=0;i<bs.length();i++) { char let = bs.charAt(i); if(!letters.containsKey(let)) { letters.put(let,0); } int tel = letters.get(let)+1; letters.put(let,tel); if(letters.get(max)<tel) { max = let; } } System.out.println(letters.get(max) + " keer " + max); } However, I'm uncertain of the time complexity of this new code: Is it O(n) because you only use one for-loop, or does the fact we require the use of the HashMap's get methods make it O(n log n) ? And if someone knows an even better way of reducing the time complexity, please do tell! :)

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  • PostMessage does not seem to be working.

    - by Vaccano
    I am trying to use PostMessage to send a tab key. Here is my code: // This class allows us to send a tab key when the the enter key // is pressed for the mooseworks mask control. public class MaskKeyControl : MaskedEdit { // [DllImport("coredll.dll", SetLastError = true, CharSet = CharSet.Auto)] // static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); [return: MarshalAs(UnmanagedType.Bool)] // I am calling this on a Windows Mobile device so the dll is coredll.dll [DllImport("coredll.dll", SetLastError = true)] static extern bool PostMessage(IntPtr hWnd, uint Msg, Int32 wParam, Int32 lParam); public const Int32 VK_TAB = 0x09; public const Int32 WM_KEYDOWN = 0x100; protected override void OnKeyDown(KeyEventArgs e) { if (e.KeyData == Keys.Enter) { PostMessage(this.Handle, WM_KEYDOWN, VK_TAB, 0); return; } base.OnKeyDown(e); } protected override void OnKeyPress(KeyPressEventArgs e) { if (e.KeyChar == '\r') e.Handled = true; base.OnKeyPress(e); } } When I press enter the code gets called, but nothing happens. Then I press TAB and it works fine. (So there is something wrong with my sending of the Tab Message.)

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  • Why am I having this InstantiationException in Java when accessing final local variables?

    - by Oscar Reyes
    I was playing with some code to make a "closure like" construct ( not working btw ) Everything looked fine but when I tried to access a final local variable in the code, the exception InstantiationException is thrown. If I remove the access to the local variable either by removing it altogether or by making it class attribute instead, no exception happens. The doc says: InstantiationException Thrown when an application tries to create an instance of a class using the newInstance method in class Class, but the specified class object cannot be instantiated. The instantiation can fail for a variety of reasons including but not limited to: - the class object represents an abstract class, an interface, an array class, a primitive type, or void - the class has no nullary constructor What other reason could have caused this problem? Here's the code. comment/uncomment the class attribute / local variable to see the effect (lines:5 and 10 ). import javax.swing.*; import java.awt.event.*; import java.awt.*; class InstantiationExceptionDemo { //static JTextField field = new JTextField();// works if uncommented public static void main( String [] args ) { JFrame frame = new JFrame(); JButton button = new JButton("Click"); final JTextField field = new JTextField();// fails if uncommented button.addActionListener( new _(){{ System.out.println("click " + field.getText()); }}); frame.add( field ); frame.add( button, BorderLayout.SOUTH ); frame.pack();frame.setVisible( true ); } } class _ implements ActionListener { public void actionPerformed( ActionEvent e ){ try { this.getClass().newInstance(); } catch( InstantiationException ie ){ throw new RuntimeException( ie ); } catch( IllegalAccessException ie ){ throw new RuntimeException( ie ); } } } Is this a bug in Java? edit Oh, I forgot, the stacktrace ( when thrown ) is: Caused by: java.lang.InstantiationException: InstantiationExceptionDemo$1 at java.lang.Class.newInstance0(Class.java:340) at java.lang.Class.newInstance(Class.java:308) at _.actionPerformed(InstantiationExceptionDemo.java:25)

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  • why DataColumn AllowDbNull is true even if oracle db does not allow null

    - by matti
    Hi. I have column SomeId in table SomeLink. When I look with tOra or Sql Plus Worksheet both state: tOra: Column name Data type Default Null Comment SOMEID INTEGER {null} NOT NULL {null} Sql Plus: SOMEID NOT NULL NUMBER(38) I have authored a method that's intended to give default values to all NOT NULL fields that don't have values: public static void GetDefaultValuesForNonNullColumns(DataRow row) { foreach(DataColumn col in row.Table.Columns) { if (Convert.IsDBNull(row[col]) && !col.AllowDBNull) { if (ColumnIsNumeric(col.DataType)) row[col] = 0; else if (col.DataType == typeof(DateTime)) row[col] = DateTime.Now; else if (col.DataType == typeof(String)) row[col] = string.Empty; else if (col.DataType == typeof(Char)) row[col] = ' '; else throw new Exception(string.Format("Unsupported column type: {0}", col.DataType)); } } } When SOMEID is handled in loop the AllowDBNull = true. I really can't understand. The table is created in DataSet like this: _someLinkAdptr = _dbFactory.CreateDataAdapter(); _someLinkAdptr.SelectCommand = _dbFactory.CreateCommand(); _someLinkAdptr.SelectCommand.Connection = _cnctn; _someLinkAdptr.SelectCommand.CommandText = GetSomeLinkSelectTxtAndParams(_someLinkAdptr.SelectCommand, UndefinedValue.ToString(), UndefinedValue.ToString()); Select command returns no rows. The idea is that I can then use commandbuilder to get InsertCommand without building it myself. The row is added to dataset's table like this: private static void CreateDocLink(int anId, int anotherId) { DataRow row = _someDataSet.Tables["SomeLink"].NewRow(); row["AnId"] = anId; row["AnotherId"] = anotherId; Utility.GetDefaultValuesForNonNullColumns(row); _someDataSet.Tables["SomeLink"].Rows.Add(row); } When DataAdapter is updated to oracle db I get: ORA-01400: cannot insert NULL into (SOMESCHEMA.SOMELINK.SOMEID) Cheers & BR -Matti

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  • COM-Objects containing maps / content error(0)

    - by Florian Berzsenyi
    I'm writing a small wrapper to get familiar with some important topics in C++ (WinAPI, COM, STL,OOP). For now, my class shall be able to create a (child) window. Mainly, this window is connected to a global message loop that distribute messages to a local loop of the right instance (global is static, local is virtual). Obviously, there are surely better ways to do that but I'm using std::maps to store HWND and their instance pointer in pairs (the Global loop looks for the pointer with the HWND-parameter, gets itself the pointer from the map and calls then the local loop). Now, it appears that the map does not accept any values because of a unknown reason. It seems to allocate enough space but something went wrong anyway [ (error) 0 is displayed instead of the entries in visual C++). I've looked that up in google as well and found out that maps cause some trouble when used in classes AND DLLs. May this be the reason and is there any solution?? Protected scope of class: static std::map<HWND,MAP_BASE_OBJECT*> m_LoopBuf Implementation in .cpp-file: std::map<HWND,MAP_BASE_OBJECT*> HWindow::m_LoopBuf;

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