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• On-Demand thumbnail creation with django and nginx

  - by sharjeel

  I want to generate thumbnails of images on the fly. My site is built with django and deployed using nginx which serves all the static content and communicates with django/apache using reverse proxy. Right now, for every image in my site, I generate all required sizes of thumbnails on-hand and deliver them when required. The problem is that whenever I change the size of a thumbnail, I have to regenerate all of them (and they are tons). However now I'd like to generate the thumbnail the first time it is accessed and later on nginx would deliver the same file over n over. If I delete that thumbnail file because of lesser accesses, it should get generated automatically the next time. Thumbnails in my case also have watermarks which require some computation logic of my application so a webserver thumbnail module might not work very well. The size of the thumbnail can be embedded in the URL. So http://www.example.com/thumbnail/abc_320x240.jpg gets the 320x240 size of the thumbnail. The approach I'm looking right now is to let nginx lookup the file and if it doesn't exist, forward the query to my django application which would create the thumbnail and send either the response or a redirect string. However I'm not sure about the concurrency issues and any other issues which might pop up later. What is the appropriate way to achieve this?

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• Strange XCode debugger behavior with UITableView datasource

  - by Tarfa

  Hey guys. I've got a perplexing issue. In my subclassed UITableViewController my datasource methods lose their tableview reference depending on lines of code I put inside the method. For example, in this code block: - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { // Return the number of sections. return 3; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // Return the number of rows in the section. return 5; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { id i = tableView; static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } // Configure the cell... return cell; } the "id i = tableView;" causes the tableview to become nil (0x0) -- and it causes it to be nil before I ever start stepping into the method. If I insert an assignment statement above the "id i = tableview;" statement: CGFloat x = 5.0; id i = tableView; then tableview retains its pointer (i.e. is not nil) if I place the breakpoint after the "id i = tableView;" line. In other words, the breakpoint must be set after the "id i = tableView"; assignment in order for tableView to retain its pointer. If the breakpoint is set before the assignment is made and I just hang at that breakpoint for a bit then after a couple of seconds the console logs this error message: Assertion failed: (cls), function getName, file /SourceCache/objc4_Sim/objc4-427.5/runtime/objc-runtime-new.mm, line 3990. Although the code works when I don't step through the method, I need my debugger to work! It makes programming kind of challenging when your debugging tools become your enemy. Anyone know what the cause and solution are? Thanks.

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• java concurrency: many writers, one reader

  - by Janning

  I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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• How do tools like Hiphop for PHP deal with heterogenous arrays?

  - by Derek Thurn

  I think HipHop for PHP is an interesting tool. It essentially converts PHP code into C++ code. Cross compiling in this manner seems like a great idea, but I have to wonder, how do they overcome the fundamental differences between the two type systems? One specific example of my general question is heterogeneous data structures. Statically typed languages don't tend to let you put arbitrary types into an array or other container because they need to be able to figure out the types on the other end. If I have a PHP array like this: $mixedBag = array("cat", 42, 8.5, false); How can this be represented in C++ code? One option would be to use void pointers (or the superior version, boost::any), but then you need to cast when you take stuff back out of the array... and I'm not at all convinced that the type inferencer can always figure out what to cast to at the other end. A better option, perhaps, would be something more like a union (or boost::variant), but then you need to enumerate all possible types at compile time... maybe possible, but certainly messy since arrays can contain arbitrarily complex entities. Does anyone know how HipHop and similar tools which go from a dynamic typing discipline to a static discipline handle these types of problems?

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• Java: 2-assignments-2-initializations inside for-loop not allowed?

  - by HH

  $ javac MatchTest.java MatchTest.java:7: ')' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: ';' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: ';' expected for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: not a statement for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ MatchTest.java:7: illegal start of expression for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) ^ 5 errors $ cat MatchTest.java import java.util.*; import java.io.*; public class MatchTest { public static void main(String[] args){ String text = "hello0123456789hello0123456789hello1234567890hello3423243423232"; for((int i=-1 && String match="hello"); (i=text.indexOf(match)+1);) System.out.println(i); } }

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• How do I tell if an action is a lambda expression?

  - by Keith

  I am using the EventAgregator pattern to subscribe and publish events. If a user subscribes to the event using a lambda expression, they must use a strong reference, not a weak reference, otherwise the expression can be garbage collected before the publish will execute. I wanted to add a simple check in the DelegateReference so that if a programmer passes in a lambda expression and is using a weak reference, that I throw an argument exception. This is to help "police" the code. Example: eventAggregator.GetEvent<RuleScheduler.JobExecutedEvent>().Subscribe ( e => resetEvent.Set(), ThreadOption.PublisherThread, false, // filter event, only interested in the job that this object started e => e.Value1.JobDetail.Name == jobName ); public DelegateReference(Delegate @delegate, bool keepReferenceAlive) { if (@delegate == null) throw new ArgumentNullException("delegate"); if (keepReferenceAlive) { this._delegate = @delegate; } else { //TODO: throw exception if target is a lambda expression _weakReference = new WeakReference(@delegate.Target); _method = @delegate.Method; _delegateType = @delegate.GetType(); } } any ideas? I thought I could check for @delegate.Method.IsStatic but I don't believe that works... (is every lambda expression a static?)

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• Java iteration reading & parsing

  - by Patrick Lorio

  I have a log file that I am reading to a string public static String Read (String path) throws IOException { StringBuilder sb = new StringBuilder(); InputStream in = new BufferedInputStream(new FileInputStream(path)); int r; while ((r = in.read()) != -1) { sb.append(r); } return sb.toString(); } Then I have a parser that iterates over the entire string once void Parse () { String con = Read("log.txt"); for (int i = 0; i < con.length; i++) { /* parsing action */ } } This is hugely a waste of cpu cycles. I loop over all the content in Read. Then I loop over all the content in Parse. I could just place the /* parsing action */ under the while loop in the Read method, which would be find but I don't want to copy the same code all over the place. How can I parse the file in one iteration over the contents and still have separate methods for parsing and reading? In C# I understand there is some sort of yield return thing, but I'm locked with Java. What are my options in Java?

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• Webmethod on my C# (server side) doesn't return data to client side (javascript)

  - by Philo

  I am using a c# Webmethod to return results to my client side written in Javascript. [WebMethod] public static string MyMethod(string Id) { SQL QUERIES and then .... // adding data to member class. Member member = new Member(Name, DOB, Sex, Member_Identification, Dates_of_services); return JsonConvert.SerializeObject(member); <-- member is a class of List strings } And on the client side you could invoke this method using the jQuery.ajax() function like this: $.ajax({ url: 'default.aspx/MyMethod', type: 'POST', contentType: 'application/json; charset=utf-8', data: JSON.stringify({ ID : ID }), success: on success { } }); function onSuccess(data) { // parses json returned data var jsondata = $.parseJSON(data.d); ..... } Now the data returned to the client side are Lists of Strings. This method works for me most times. However for one or two queries, the method runs forever without returning to the client side. On the server side however, I can use breakpoints and see that all the Lists of strings have been formed correctly. But I cannot seem to find out why they are never returned to the client side. My code reaches till the return statement on the server side and then the program just runs forever. It never reaches the function 'onsuccess' Can anyone tell me why this can happen? Anomalies in data maybe?

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• Best way to detect similar email addresses?

  - by Chris

  I have a list of ~20,000 email addresses, some of which I know to be fraudulent attempts to get around a "1 per e-mail" limit. ([email protected], [email protected], [email protected], etc...). I want to find similar email addresses for evaluation. Currently I'm using a levenshtein algorithm to check each e-mail against the others in the list and report any with an edit distance of less than 2. However, this is painstakingly slow. Is there a more efficient approach? The test code I'm using now is: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; namespace LevenshteinAnalyzer { class Program { const string INPUT_FILE = @"C:\Input.txt"; const string OUTPUT_FILE = @"C:\Output.txt"; static void Main(string[] args) { var inputWords = File.ReadAllLines(INPUT_FILE); var outputWords = new SortedSet<string>(); for (var i = 0; i < inputWords.Length; i++) { if (i % 100 == 0) Console.WriteLine("Processing record #" + i); var word1 = inputWords[i].ToLower(); for (var n = i + 1; n < inputWords.Length; n++) { if (i == n) continue; var word2 = inputWords[n].ToLower(); if (word1 == word2) continue; if (outputWords.Contains(word1)) continue; if (outputWords.Contains(word2)) continue; var distance = LevenshteinAlgorithm.Compute(word1, word2); if (distance <= 2) { outputWords.Add(word1); outputWords.Add(word2); } } } File.WriteAllLines(OUTPUT_FILE, outputWords.ToArray()); Console.WriteLine("Found {0} words", outputWords.Count); } } }

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• How-to display a .gif as background image?

  - by Vito De Tullio

  Hi! I have a javascript "loading" function like this: function splashScreen() { var div = document.createElement('div'); div.appendChild(document.createTextNode("some text")); div.setAttribute("style", "position: fixed; " + "width: 100%; height: 100%; " + "left: 0; top: 0; " + "z-index: 1000; " + "background: #fff url('img/loading.gif') no-repeat center; " + "font-size: x-large; " + "text-align: center; " + "line-height: 3em; " + "opacity: 0.75; " + "filter: alpha(opacity=75); "); document.getElementsByTagName('body')[0].appendChild(div); return true; } I use this function in the form action (onsubmit="return splashScreen()") to show a "rotating logo" while the next page load... The problem is in that "img/loading.gif" and safari (on winXP): in ff and ie I have no problems, and I clearly see the animated gif. In safari I can't see it. If I change the image with a (obviously static) png the image appears... Am I doing something wrong? What's the problem with safari?

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• problem in adding image to JFrame

  - by firestruq

  Hi, I'm having problems in adding a picture into JFrame, something is missing probebly or written wrong. here are the classes: main class: public class Tester { public static void main(String args[]) { BorderLayoutFrame borderLayoutFrame = new BorderLayoutFrame(); borderLayoutFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); borderLayoutFrame.setSize(600,600); borderLayoutFrame.setVisible(true); } } public class BorderLayoutFrame extends JFrame implements ActionListener { private JButton buttons[]; // array of buttons to hide portions private final String names[] = { "North", "South", "East", "West", "Center" }; private BorderLayout layout; // borderlayout object private PicPanel picture = new PicPanel(); // set up GUI and event handling public BorderLayoutFrame() { super( "Philosofic Problem" ); layout = new BorderLayout( 5, 5 ); // 5 pixel gaps setLayout( layout ); // set frame layout buttons = new JButton[ names.length ]; // set size of array // create JButtons and register listeners for them for ( int count = 0; count < names.length; count++ ) { buttons[ count ] = new JButton( names[ count ] ); buttons[ count ].addActionListener( this ); } add( buttons[ 0 ], BorderLayout.NORTH ); // add button to north add( buttons[ 1 ], BorderLayout.SOUTH ); // add button to south add( buttons[ 2 ], BorderLayout.EAST ); // add button to east add( buttons[ 3 ], BorderLayout.WEST ); // add button to west add( picture, BorderLayout.CENTER ); // add button to center } // handle button events public void actionPerformed( ActionEvent event ) { } } I'v tried to add the image into the center of layout. here is the image class: public class PicPanel extends JPanel { Image img; private int width = 0; private int height = 0; public PicPanel() { super(); img = Toolkit.getDefaultToolkit().getImage("table.jpg"); } public void paintComponent(Graphics g) { super.paintComponents(g); if ((width <= 0) || (height <= 0)) { width = img.getWidth(this); height = img.getHeight(this); } g.drawImage(img,0,0,width,height,this); } } Please your help, what is the problem? thanks BTW: i'm using eclipse, which directory the image suppose to be in?

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• .NET - Is there a way to programmatically fill all tables in a strongly-typed dataset?

  - by Mike Loux

  Hello, all! I have a SQL Server database for which I have created a strongly-typed DataSet (using the DataSet Designer in Visual Studio 2008), so all the adapters and select commands and whatnot were created for me by the wizard. It's a small database with largely static data, so I would like to pull the contents of this DB in its entirety into my application at startup, and then grab individual pieces of data as needed using LINQ. Rather than hard-code each adapter Fill call, I would like to see if there is a way to automate this (possibly via Reflection). So, instead of: Dim _ds As New dsTest dsTestTableAdapters.Table1TableAdapter.Fill(_ds.Table1) dsTestTableAdapters.Table2TableAdapter.Fill(_ds.Table2) <etc etc etc> I would prefer to do something like: Dim _ds As New dsTest For Each tableName As String In _ds.Tables Dim adapter as Object = <routine to grab adapter associated with the table> adapter.Fill(tableName) Next Is that even remotely doable? I have done a fair amount of searching, and I wouldn't think this would be an uncommon request, but I must be either asking the wrong question, or I'm just weird to want to do this. I will admit that I usually prefer to use unbound controls and not go with strongly-typed datasets (I prefer to write SQL directly), but my company wants to go this route, so I'm researching it. I think the idea is that as tables are added, we can just refresh the DataSet using the Designer in Visual Studio and not have to make too many underlying DB code changes. Any help at all would be most appreciated. Thanks in advance!

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• Creating and writing file from a FileOutputStream in Java

  - by Althane

  Okay, so I'm working on a project where I use a Java program to initiate a socket connection between two classes (a FileSender and FileReceiver). My basic idea was that the FileSender would look like this: try { writer = new DataOutputStream(connect.getOutputStream()); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } //While we have bytes to send while(filein.available() >0){ //We write them out to our buffer writer.write(filein.read(outBuffer)); writer.flush(); } //Then close our filein filein.close(); //And then our socket; connect.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); The constructor contains code that checks to see if the file exists, and that the socket is connected, and so on. Inside my FileReader is this though: input = recvSocket.accept(); BufferedReader br = new BufferedReader(new InputStreamReader(input.getInputStream())); FileOutputStream fOut= new FileOutputStream(filename); String line = br.readLine(); while(line != null){ fOut.write(line.getBytes()); fOut.flush(); line = br.readLine(); } System.out.println("Before RECV close statements"); fOut.close(); input.close(); recvSocket.close(); System.out.println("After RECV clsoe statements"); All inside a try-catch block. So, what I'm trying to do is have the FileSender reading in the file, converting to bytes, sending and flushing it out. FileReceiver, then reads in the bytes, writes to the fileOut, flushes, and continues waiting for more. I make sure to close all the things that I open, so... here comes the weird part. When I try and open the created text file in Eclipse, it tells me "An SWT error has occured ... recommended to exit the workbench... see .log for more details.". Another window pops up saying "Unhandled event loop exception, (no more handles)". However, if I try to open the sent text file in notepad2, I get ThisIsASentTextfile Which is good (well, minus the fact that there should be line breaks, but I'm working on that...). Does anyone know why this is happening? And while we're checking, how to add the line breaks? (And is this a particularly bad way to transfer files over java without getting some other libraries?)

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• using volatile keyword

  - by sap

  As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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• Name for method that takes a string value and returns DBNull.Value || string

  - by David Murdoch

  I got tired of writing the following code: /* Commenting out irrelevant parts public string MiddleName; public void Save(){ SqlCommand = new SqlCommand(); // blah blah...boring INSERT statement with params etc go here. */ if(MiddleName==null){ myCmd.Parameters.Add("@MiddleName", DBNull.Value); } else{ myCmd.Parameters.Add("@MiddleName", MiddleName); } /* // more boring code to save to DB. }*/ So, I wrote this: public static object DBNullValueorStringIfNotNull(string value) { object o; if (value == null) { o = DBNull.Value; } else { o = value; } return o; } // which would be called like: myCmd.Parameters.Add("@MiddleName", DBNullValueorStringIfNotNull(MiddleName)); If this is a good way to go about doing this then what would you suggest as the method name? DBNullValueorStringIfNotNull is a bit verbose and confusing. I'm also open to ways to alleviate this problem entirely. I'd LOVE to do this: myCmd.Parameters.Add("@MiddleName", MiddleName==null ? DBNull.Value : MiddleName); but that won't work. I've got C# 3.5 and SQL Server 2005 at my disposal if it matters.

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• python packaging causes importerror

  - by Absolute0

  I am getting an annoying import error when I try to import a variable in an init.py file. I have attached the files involved and my directory structure: #/home/me/app/app/__init__.py from flaskext.sqlalchemy import SQLAlchemy db = SQLAlchemy(app) #/home/me/app/app/models/__init__.py from datetime import datetime from app import db #shell [me@archlinux app]$ pwd /home/me/app [me@archlinux app]$ ./manage.py /home/me/app/app/__init__.pyc Traceback (most recent call last): File "./manage.py", line 7, in <module> from app import app File "/home/me/app/app/__init__.py", line 3, in <module> from app.views.post import post File "/home/me/app/app/views/post.py", line 4, in <module> from app.models import Post File "/home/me/app/app/models/__init__.py", line 5, in <module> from app import db ImportError: cannot import name db [me@archlinux app]$ tree . +-- apikey.txt +-- manage.py +-- app ¦   +-- forms ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   +-- __init__.py ¦   +-- __init__.py~ ¦   +-- __init__.pyc ¦   +-- models ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   ¦   +-- __init__.pyc ¦   +-- static ¦   ¦   +-- css ¦   ¦   ¦   +-- style.css ¦   ¦   +-- images ¦   ¦   ¦   +-- favicon.png ¦   ¦   ¦   +-- logo.png ¦   ¦   ¦   +-- text_logo.png ¦   ¦   ¦   +-- thumb_down_active.png ¦   ¦   ¦   +-- thumb_down_inactive.png ¦   ¦   ¦   +-- thumb_up_active.png ¦   ¦   ¦   +-- thumb_up_inactive.png ¦   ¦   +-- js ¦   ¦   ¦   +-- index.js ¦   ¦   +-- sitemap.xml ¦   +-- templates ¦   ¦   +-- 404.html ¦   ¦   +-- 500.html ¦   ¦   +-- about.html ¦   ¦   +-- base.html ¦   ¦   +-- feedback ¦   ¦   ¦   +-- feedback_form.html ¦   ¦   +-- form.html ¦   ¦   +-- posts ¦   ¦   ¦   +-- comment.html ¦   ¦   ¦   +-- post.html ¦   ¦   ¦   +-- posts.html ¦   ¦   +-- spam.html ¦   ¦   +-- terms.html ¦   ¦   +-- users ¦   ¦   +-- login_form.html ¦   ¦   +-- sign_up_form.html ¦   +-- util ¦   ¦   +-- forms.py ¦   ¦   +-- honeypot.py ¦   ¦   +-- __init__.py ¦   ¦   +-- __init__.py~ ¦   ¦   +-- json_http.py ¦   ¦   +-- models.py ¦   ¦   +-- spam.py ¦   +-- views ¦   +-- feedback.py ¦   +-- __init__.py ¦   +-- __init__.pyc ¦   +-- post.py ¦   +-- post.pyc ¦   +-- user.py +-- settings.py +-- settings.pyc +-- TiddlyWiki.html 13 directories, 49 files What might be the problem?

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• Generate java class and call it's method dynamically

  - by Jacob

  package reflection; import java.io.*; import java.lang.reflect.*; class class0 { public void writeout0() { System.out.println("class0"); } } class class1 { public void writeout1() { System.out.println("class1"); } } class class2 { public void writeout2() { System.out.println("class2"); } } class class3 { public void run() { try { BufferedReader reader= new BufferedReader(new InputStreamReader (System.in)); String line=reader.readLine(); Class cls=Class.forName(line); //define method here } catch(Exception ee) { System.out.println("here "+ee); } } public void writeout3() { System.out.println("class3"); } } class class4 { public void writeout4() { System.out.println("class4"); } } class class5 { public void writeout5() { System.out.println("class5"); } } class class6 { public void writeout6() { System.out.println("class6"); } } class class7 { public void writeout7() { System.out.println("class7"); } } class class8 { public void writeout8() { System.out.println("class8"); } } class class9 { public void writeout9() { System.out.println("class9"); } } class testclass { public static void main(String[] args) { System.out.println("Write class name : "); class3 example=new class3(); example.run(); } } Question is ; third class will read the name of the class as String from console. Upon reading the name of the class, it will automatically and dynamically generate that class and call its writeout method.If that class is not read from input, it will not be initialized. but I can't continue any more ; i need to more something for 3.class, what can i do? Thanks;

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• What version of .NET containing RuntimeMethodHandle.EmptyHandle?

  - by user299990

  No one answers my question in http://stackoverflow.com/questions/1295344/difference-between-activator-createinstance-and-typeoft-invokemember-with-b/2500960#2500960. I guess that the issue is closed and I am asking here again. Ben M have a nice function which I need for a project. The function is - public static T CreateInstance() { bool bNeedSecurityCheck = true; bool canBeCached = false; RuntimeMethodHandle emptyHandle = RuntimeMethodHandle.EmptyHandle; return (T) RuntimeTypeHandle.CreateInstance(typeof(T) as RuntimeType, true, true, ref canBeCached, ref emptyHandle, ref bNeedSecurityCheck); } I am using .NET 3.5 and Visual studio 2008. It gives the error "EmptyHandle type name does not exist in the type System.RuntimeMethodHandle". Then I used "RuntimeMethodHandle emptyHandle = new RuntimeMethodHandle();". Another error presents. RuntimeTypeHandle does not have a CreateInstance method either. Activator has. But it does not take any ref parameter. Thanks for clarification in advance!

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• Using XPath on String in Android (JAVA)

  - by Rav

  I am looking for some examples of using xpath in Android? Or if anyone can share their experiences. I have been struggeling to make tail or head of this problem :-( I have a string that contains a standard xml file. I believe I need to convert that into an xml document. I have found this code which I think will do the trick: public static Document stringToDom(String xmlSource) throws SAXException, ParserConfigurationException, IOException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); return builder.parse(new InputSource(new StringReader(xmlSource))); } Next steps Assuming the code above is OK, I need to apply xpath to get values from cat: "/animal/mammal/feline/cat" I look at the dev doc here: http://developer.android.com/reference/javax/xml/xpath/XPath.html and also look online, but I am not sure where to start! I have tried to use the following code: XPathFactory xPathFactory = XPathFactory.newInstance(); // To get an instance of the XPathFactory object itself. XPath xPath = xPathFactory.newXPath(); // Create an instance of XPath from the factory class. String expression = "SomeXPathExpression"; XPathExpression xPathExpression = xPath.compile(expression); // Compile the expression to get a XPathExpression object. Object result = xPathExpression.evaluate(xmlDocument); // Evaluate the expression against the XML Document to get the result. But I get "Cannot be resolved". Eclipse doesn't seem to be able to fix this import. I tried manually entering: javax.xml.xpath.XPath But this did not work. Does anyone know any good source code that I can utilise, for Android platform? 1.5

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• C# Select clause returns system exception instead of relevant object

  - by Kashif

  I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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• Hiding/blocking tabs using windows forms in c#

  - by Audel

  The thing is that i have a 'log in window' and a 'mainwindow' that is called after pressing the log in button or the "VISITANT" button If pressing the log in button, the whole system will come out, and if i press the VISITANT button, one tab should disappear or be blocked or something. private void visitant(object sender, EventArgs e) { mainwindow menu = new mainwindow(); menu.Show(); //mainwindow.tabPage1.Enabled = false; //attempt1 //mainwindow.tabPage1.Visible = false; //attempt1 //System.Windows.Forms.tabPage1.Enabled = false;//attempt2 //System.Windows.Forms.tabPage1.Visible = false;//attempt2 this.Hide(); } the errors i get for using the attempt1 are Error 1 'System.mainwindow.tabPage1' is inaccessible due to its protection level' Error 2 An object reference is required for the non-static field, method, or property 'System.mainwindow.tabPage1' and the one i get for using the attempt2 is Error 1 The type or namespace name 'tabPage1' does not exist in the namespace 'System.Windows.Forms' (are you missing an assembly reference?) as you probably have guessed "tabPage1" is the tab i need to hide when pressing the visitant button. I can't think of any more details, I will be around to provide any extra information Thanks in advance.

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• Windows SQL wildcards and ASP.net parameters

  - by Vinzcent

  Hey In my SQL statement I use wildcards. But when I try to select something, it never select something. While when I execute the querry in Microsoft SQL Studio, it works fine. What am I doing wrong? Click handler protected void btnTitelAuteur_Click(object sender, EventArgs e) { cvalTitelAuteur.Enabled = true; cvalTitelAuteur.Validate(); if (Page.IsValid) { objdsSelectedBooks.SelectMethod = "getBooksByTitleAuthor"; objdsSelectedBooks.SelectParameters.Clear(); objdsSelectedBooks.SelectParameters.Add(new Parameter("title", DbType.String)); objdsSelectedBooks.SelectParameters.Add(new Parameter("author", DbType.String)); objdsSelectedBooks.Select(); gvSelectedBooks.DataBind(); pnlZoeken.Visible = false; pnlKiezen.Visible = true; } } In my Data Acces Layer public static DataTable getBooksByTitleAuthor(string title, string author) { string sql = "SELECT 'AUTHOR' = tblAuthors.FIRSTNAME + ' ' + tblAuthors.LASTNAME, tblBooks.*, tblGenres.GENRE " + "FROM tblAuthors INNER JOIN tblBooks ON tblAuthors.AUTHOR_ID = tblBooks.AUTHOR_ID INNER JOIN tblGenres ON tblBooks.GENRE_ID = tblGenres.GENRE_ID " +"WHERE (tblBooks.TITLE LIKE '%@title%');"; SqlDataAdapter da = new SqlDataAdapter(sql, GetConnectionString()); da.SelectCommand.Parameters.Add("@title", SqlDbType.Text); da.SelectCommand.Parameters["@title"].Value = title; DataSet ds = new DataSet(); da.Fill(ds, "Books"); return ds.Tables["Books"]; } Thanks, Vincent

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• 'Bank Switching' Sprites on old NES applications

  - by Jeffrey Kern

  I'm currently writing in C# what could basically be called my own interpretation of the NES hardware for an old-school looking game that I'm developing. I've fired up FCE and have been observing how the NES displayed and rendered graphics. In a nutshell, the NES could hold two bitmaps worth of graphical information, each with the dimensions of 128x128. These are called the PPU tables. One was for BG tiles and the other was for sprites. The data had to be in this memory for it to be drawn on-screen. Now, if a game had more graphical data then these two banks, it could write portions of this new information to these banks -overwriting what was there - at the end of each frame, and use it from the next frame onward. So, in old games how did the programmers 'bank switch'? I mean, within the level design, how did they know which graphic set to load? I've noticed that Mega Man 2 bankswitches when the screen programatically scrolls from one portion of the stage to the next. But how did they store this information in the level - what sprites to copy over into the PPU tables, and where to write them at? Another example would be hitting pause in MM2. BG tiles get over-written during pause, and then get restored when the player unpauses. How did they remember which tiles they replaced and how to restore them? If I was lazy, I could just make one huge static bitmap and just grab values that way. But I'm forcing myself to limit these values to create a more authentic experience. I've read the amazing guide on how M.C. Kids was made, and I'm trying to be barebones about how I program this game. It still just boggles my mind how these programmers accomplisehd what they did with what they had. EDIT: The only solution I can think of would be to hold separate tables that state what tiles should be in the PPU at what time, but I think that would be a huge memory resource that the NES wouldn't be able to handle.

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• Entity Framework looking for wrong column

  - by m.edmondson

  I'm brand new to the Entity Framework and trying to learn all it can offer. I'm currently working my way through the MVC Music Store tutorial which includes the following code: public ActionResult Browse(string genre) { // Retrieve Genre and its Associated Albums from database var genreModel = storeDB.Genres.Include("Albums") .Single(g => g.Name == genre); return View(genreModel); } as I'm working in VB I converted it like so: Function Browse(ByVal genre As String) As ActionResult 'Retrieve Genre and its Associated Albums from database Dim genreModel = storeDB.Genres.Include("Albums"). _ Single(Function(g) g.Name = genre) Return(View(genreModel)) End Function The problem is I'm getting the following exception: Invalid column name 'GenreGenreId'. Which I know is true, but I can't for the life of my work out where it's getting 'GenreGenreId' from. Probably a basic question but I'll appreciate any help in the right direction. As per requested here is the source for my classes: Album.vb Public Class Album Private _title As String Private _genre As Genre Private _AlbumId As Int32 Private _GenreId As Int32 Private _ArtistId As Int32 Private _Price As Decimal Private _AlbumArtUrl As String Public Property Title As String Get Return _title End Get Set(ByVal value As String) _title = value End Set End Property Public Property AlbumId As Int16 Get Return _AlbumId End Get Set(ByVal value As Int16) _AlbumId = value End Set End Property Public Property GenreId As Int16 Get Return _GenreId End Get Set(ByVal value As Int16) _GenreId = value End Set End Property Public Property ArtistId As Int16 Get Return _ArtistId End Get Set(ByVal value As Int16) _ArtistId = value End Set End Property Public Property AlbumArtUrl As String Get Return _AlbumArtUrl End Get Set(ByVal value As String) _AlbumArtUrl = value End Set End Property Public Property Price As Decimal Get Return _Price End Get Set(ByVal value As Decimal) _Price = value End Set End Property Public Property Genre As Genre Get Return _genre End Get Set(ByVal value As Genre) _genre = value End Set End Property End Class Genre.vb Public Class Genre Dim _genreId As Int32 Dim _Name As String Dim _Description As String Dim _Albums As List(Of Album) Public Property GenreId As Int32 Get Return _genreId End Get Set(ByVal value As Int32) _genreId = value End Set End Property Public Property Name As String Get Return _Name End Get Set(ByVal value As String) _Name = value End Set End Property Public Property Description As String Get Return _Description End Get Set(ByVal value As String) _Description = value End Set End Property Public Property Albums As List(Of Album) Get Return _Albums End Get Set(ByVal value As List(Of Album)) _Albums = value End Set End Property End Class MusicStoreEntities.vb Imports System.Data.Entity Namespace MvcApplication1 Public Class MusicStoreEntities Inherits DbContext Public Property Albums As DbSet(Of Album) Public Property Genres As DbSet(Of Genre) End Class End Namespace

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• Associate File Extension with Application

  - by fneep

  I've written a program that edits a specific filetype , and I want to give the user the option to set my application as the default editor for this filetype (since I don't want an installer) on startup. I've tried to write a re-useable method that associates a file for me (preferably on any OS, although I'm running Vista) by adding a key to HKEY_CLASSES_ROOT, and am using it with my application, but it doesn't seem to work. public static void SetAssociation(string Extension, string KeyName, string OpenWith, string FileDescription) { RegistryKey BaseKey; RegistryKey OpenMethod; RegistryKey Shell; RegistryKey CurrentUser; BaseKey = Registry.ClassesRoot.CreateSubKey(Extension); BaseKey.SetValue("", KeyName); OpenMethod = Registry.ClassesRoot.CreateSubKey(KeyName); OpenMethod.SetValue("", FileDescription); OpenMethod.CreateSubKey("DefaultIcon").SetValue("", "\"" + OpenWith + "\",0"); Shell = OpenMethod.CreateSubKey("Shell"); Shell.CreateSubKey("edit").CreateSubKey("command").SetValue("", "\"" + OpenWith + "\"" + " \"%1\""); Shell.CreateSubKey("open").CreateSubKey("command").SetValue("", "\"" + OpenWith + "\"" + " \"%1\""); BaseKey.Close(); OpenMethod.Close(); Shell.Close(); CurrentUser = Registry.CurrentUser.CreateSubKey(@"HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.ucs"); CurrentUser = CurrentUser.OpenSubKey("UserChoice", RegistryKeyPermissionCheck.ReadWriteSubTree, System.Security.AccessControl.RegistryRights.FullControl); CurrentUser.SetValue("Progid", KeyName, RegistryValueKind.String); CurrentUser.Close(); }

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