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• Dynamically added JTable not displaying

  - by Graza

  Java Newbie here. I have a JFrame that I added to my netbeans project, and I've added the following method to it, which creates a JTable. Problem is, for some reason when I call this method, the JTable isn't displayed. Any suggestions? public void showFromVectors(Vector colNames, Vector data) { jt = new javax.swing.JTable(data, colNames); sp = new javax.swing.JScrollPane(jt); //NB: "this" refers to my class DBGridForm, which extends JFrame this.add(sp,java.awt.BorderLayout.CENTER); this.setSize(640,480); } The method is called in the following context: DBGridForm gf = new DBGridForm(); //DBGridForm extends JFrame DBReader.outMatchesTable(gf); gf.setVisible(true); ... where DBReader.outMatchesTable() is defined as static public void outMatchesTable(DBGridForm gf) { DBReader ddb = new DBReader(); ddb.readMatchesTable(null); gf.showFromVectors(ddb.lastRsltColNames, ddb.lastRsltData); } My guess is I'm overlooking something, either about the swing classes I'm using, or about Java. Any ideas?

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• paging helper asp.net mvc

  - by csetzkorn

  Hi, I have implemented a paging html helper (adapted from steven sanderson's book). This is the current code: public static string PageLinks(this HtmlHelper html, int currentPage, int totalPages, Func pageUrl) { StringBuilder result = new StringBuilder(); for (int i = 1; i <= totalPages; i++) { TagBuilder tag = new TagBuilder("a"); tag.MergeAttribute("href", pageUrl(i)); tag.InnerHtml = i.ToString(); if (i == currentPage) tag.AddCssClass("selectedPage"); result.AppendLine(tag.ToString()); } return result.ToString(); } This produces a bunch of links to each page of my items. If there are many pages this can be a bit overwhelming. I am looking for a similar implementation which produces something less overwhelming like this: where 6 is the current page. I am sure someone must have implemented something similar ... before I have to re-implement the wheel. Thanks. Christian

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• Slow Python HTTP server on localhost

  - by Abiel

  I am experiencing some performance problems when creating a very simple Python HTTP server. The key issue is that performance is varying depending on which client I use to access it, where the server and all clients are being run on the local machine. For instance, a GET request issued from a Python script (urllib2.urlopen('http://localhost/').read()) takes just over a second to complete, which seems slow considering that the server is under no load. Running the GET request from Excel using MSXML2.ServerXMLHTTP also feels slow. However, requesting the data Google Chrome or from RCurl, the curl add-in for R, yields an essentially instantaneous response, which is what I would expect. Adding further to my confusion is that I do not experience any performance problems for any client when I am on my computer at work (the performance problems are on my home computer). Both systems run Python 2.6, although the work computer runs Windows XP instead of 7. Below is my very simple server example, which simply returns 'Hello world' for any get request. from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer class MyHandler(BaseHTTPRequestHandler): def do_GET(self): print("Just received a GET request") self.send_response(200) self.send_header("Content-type", "text/html") self.end_headers() self.wfile.write('Hello world') return def log_request(self, code=None, size=None): print('Request') def log_message(self, format, *args): print('Message') if __name__ == "__main__": try: server = HTTPServer(('localhost', 80), MyHandler) print('Started http server') server.serve_forever() except KeyboardInterrupt: print('^C received, shutting down server') server.socket.close() Note that in MyHandler I override the log_request() and log_message() functions. The reason is that I read that a fully-qualified domain name lookup performed by one of these functions might be a reason for a slow server. Unfortunately setting them to just print a static message did not solve my problem. Also, notice that I have put in a print() statement as the first line of the do_GET() routine in MyHandler. The slowness occurs prior to this message being printed, meaning that none of the stuff that comes after it is causing a delay.

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• Version Control: multiple version hell, file synchronization

  - by SigTerm

  Hello. I would like to know how you normally deal with this situation: I have a set of utility functions. Say..5..10 files. And technically they are static library, cross-platform - SConscript/SConstruct plus Visual Studio project (not solution). Those utility functions are used in multiple small projects (15+, number increases over time). Each project has a copy of a few files or of an entire library, not a link into one central place. Sometimes project uses one file, two files, some use everything. Normally, utility functions are included as a copy of every file and SConscript/SConstruct or Visual Studio Project (depending on the situation). Each project has a separate git repository. Sometimes one project is derived from other, sometimes it isn't. You work on every one of them, in random order. There are no other people (to make things simpler) The problem arises when while working on one project you modify those utility function files. Because each project has a copy of file, this introduces new version, which leads to the mess when you try later (week later, for example) to guess which version has a most complete functionality (i.e. you added a function to a.cpp in one project, and added another function to a.cpp in another project, which created a version fork) How would you handle this situation to avoid "version hell"? One way I can think of is using symbolic links/hard links, but it isn't perfect - if you delete one central storage, it will all go to hell. And hard links won't work on dual-boot system (although symbolic links will). It looks like what I need is something like advanced git repository, where code for the project is stored in one local repository, but is synchronized with multiple external repositories. But I'm not sure how to do it or if it is possible to do this with git. So, what do you think?

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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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• Is this a good or bad way to use constructor chaining? (... to allow for testing).

  - by panamack

  My motivation for chaining my class constructors here is so that I have a default constructor for mainstream use by my application and a second that allows me to inject a mock and a stub. It just seems a bit ugly 'new'-ing things in the ":this(...)" call and counter-intuitive calling a parametrized constructor from a default constructor , I wondered what other people would do here? (FYI - SystemWrapper) using SystemWrapper; public class MyDirectoryWorker{ // SystemWrapper interface allows for stub of sealed .Net class. private IDirectoryInfoWrap dirInf; private FileSystemWatcher watcher; public MyDirectoryWorker() : this( new DirectoryInfoWrap(new DirectoryInfo(MyDirPath)), new FileSystemWatcher()) { } public MyDirectoryWorker(IDirectoryInfoWrap dirInf, FileSystemWatcher watcher) { this.dirInf = dirInf; if(!dirInf.Exists){ dirInf.Create(); } this.watcher = watcher; watcher.Path = dirInf.FullName; watcher.NotifyFilter = NotifyFilters.FileName; watcher.Created += new FileSystemEventHandler(watcher_Created); watcher.Deleted += new FileSystemEventHandler(watcher_Deleted); watcher.Renamed += new RenamedEventHandler(watcher_Renamed); watcher.EnableRaisingEvents = true; } public static string MyDirPath{get{return Settings.Default.MyDefaultDirPath;}} // etc... }

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• URL naming conventions

  - by LookitsPuck

  So, this may be a can of worms. But I'm curious what your practices are? For example, let's say your website consists of the following needs (very basic): A landing page An information page for an event (static) A listing of places for that event (dynamic) An information page for each place With that said, how would you design your URLs? Typically, I'd do something like the following: www.domain.com/ - landing page [also accessible via www.domain.com/home] www.domain.com/event - event information page www.domain.com/places - listing of all places www.domain.com/places/{id} - place information page Now, here's a question. Just grammatically speaking, I have a hangup of referring to a given place in a url as being plural. Shouldn't it make more sense to go with this: www.domain.com/place/{id} as opposed to www.domain.com/places/{id} In some frameworks, you have a convention to follow (for example, ASP.NET MVC) by default. Yes, you can define custom routes to have /place/{id} route to the PlacesController. However, I'm just trying to keep this a bit abstract in discussion. With that being said, let's see for instance on another page of your site, you have a link, that when clicked, would open a modal popup populated with place information. Where you place that information? We could go with something like this: www.domain.com/ajax/places/{id} OR www.domain.com/places/{id} and serve based on the request header (that is, if requesting JSON, return JSON?}. Finally, for SEO reasons, typically I use a slug associated with a given resource. So, something like such: www.domain.com/ajax/places/{id}/london Where london is only there to add decoration to the link for SEO reasons. Is this sound? I ask all of these questions, because these are practices that I've been using for awhile, and I'd just like to see what other developers are doing or if I'm approaching things incorrectly. Thanks!

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• Why is this attempt at a binary search crashing?

  - by Ian Campbell

  I am fairly new to the concept of a binary search, and am trying to write a program that does this in Java for personal practice. I understand the concept of this well, but my code is not working. There is a run-time exception happening in my code that just caused Eclipse, and then my computer, to crash... there are no compile-time errors here though. Here is what I have so far: public class BinarySearch { // instance variables int[] arr; int iterations; // constructor public BinarySearch(int[] arr) { this.arr = arr; iterations = 0; } // instance method public int findTarget(int targ, int[] sorted) { int firstIndex = 1; int lastIndex = sorted.length; int middleIndex = (firstIndex + lastIndex) / 2; int result = sorted[middleIndex - 1]; while(result != targ) { if(result > targ) { firstIndex = middleIndex + 1; middleIndex = (firstIndex + lastIndex) / 2; result = sorted[middleIndex - 1]; iterations++; } else { lastIndex = middleIndex + 1; middleIndex = (firstIndex + lastIndex) / 2; result = sorted[middleIndex - 1]; iterations++; } } return result; } // main method public static void main(String[] args) { int[] sortedArr = new int[] { 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29 }; BinarySearch obj = new BinarySearch(sortedArr); int target = sortedArr[8]; int result = obj.findTarget(target, sortedArr); System.out.println("The original target was -- " + target + ".\n" + "The result found was -- " + result + ".\n" + "This took " + obj.iterations + " iterations to find."); } // end of main method } // end of class BinarySearch

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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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• commons-exec: hanging when I call executor.execute(commandLine);

  - by Stefan Kendall

  I have no idea why this is hanging. I'm trying to capture output from a process run through commons-exec, and I continue to hang. I've provided an example program to demonstrate this behavior below. import java.io.DataInputStream; import java.io.IOException; import java.io.PipedInputStream; import java.io.PipedOutputStream; import org.apache.commons.exec.CommandLine; import org.apache.commons.exec.DefaultExecutor; import org.apache.commons.exec.ExecuteException; import org.apache.commons.exec.PumpStreamHandler; public class test { public static void main(String[] args) { String command = "java"; PipedOutputStream output = new PipedOutputStream(); PumpStreamHandler psh = new PumpStreamHandler(output); CommandLine cl = CommandLine.parse(command); DefaultExecutor exec = new DefaultExecutor(); DataInputStream is = null; try { is = new DataInputStream(new PipedInputStream(output)); exec.setStreamHandler(psh); exec.execute(cl); } catch (ExecuteException ex) { } catch (IOException ex) { } System.out.println("huh?"); } }

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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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• 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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• 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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• .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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• ffmpeg mp3 convertion

  - by Alex

  was to convert several thousand MP3 files, and get this for some files: ffmpeg -t 45 -i "public/system/musics/files/2009/original/03_Memphis.mp3" -y "memphis.mp3" FFmpeg version 0.5-svn17737+3:0.svn20090303-1ubuntu6, Copyright (c) 2000-2009 Fabrice Bellard, et al. configuration: --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --extra-version=svn17737+3:0.svn20090303-1ubuntu6 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --disable-stripping --disable-vhook --enable-libdc1394 --disable-armv5te --disable-armv6 --disable-armv6t2 --disable-armvfp --disable-neon --disable-altivec --disable-vis --enable-shared --disable-static libavutil 49.15. 0 / 49.15. 0 libavcodec 52.20. 0 / 52.20. 0 libavformat 52.31. 0 / 52.31. 0 libavdevice 52. 1. 0 / 52. 1. 0 libavfilter 0. 4. 0 / 0. 4. 0 libswscale 0. 7. 1 / 0. 7. 1 libpostproc 51. 2. 0 / 51. 2. 0 built on Apr 10 2009 23:18:41, gcc: 4.3.3 public/system/musics/files/2009/original/03_Memphis.mp3: could not find codec parameters what could be the problem?

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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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• '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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• 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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• 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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• 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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• 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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• Constructor Overloading

  - by Mark Baker

  Normally when I want to create a class constructor that accepts different types of parameters, I'll use a kludgy overloading principle of not defining any args in the constructor definition: e.g. for an ECEF coordinate class constructor, I want it to accept either $x, $y and $z arguments, or to accept a single array argument containg x, y and z values, or to accept a single LatLong object I'd create a constructor looking something like: function __construct() { // Identify if any arguments have been passed to the constructor if (func_num_args() > 0) { $args = func_get_args(); // Identify the overload constructor required, based on the datatype of the first argument $argType = gettype($args[0]); switch($argType) { case 'array' : // Array of Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromArray'; break; case 'object' : // A LatLong object that needs converting to Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromLatLong'; break; default : // Individual Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromXYZ'; break; } // Call the appropriate overload constructor call_user_func_array(array($this,$overloadConstructor),$args); } } // function __construct() I'm looking at an alternative: to provide a straight constructor with $x, $y and $z as defined arguments, and to provide static methods of createECEFfromArray() and createECEFfromLatLong() that handle all the necessary extraction of x, y and z; then create a new ECEF object using the standard constructor, and return that Which option is cleaner from an OO purists perspective?

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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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• Write a program which works out which is the lowest priced computer in an ArrayList of computer obje

  - by Eoin

  Hello everybody! I am trying to study some java and cannot get my head around this question! Any help would be really appreciated and would help me in further studies! Thank you so much in advance! Eoin from Dublin, Ireland. ArrayList of Objects Write a program which works out which is the lowest priced computer in an ArrayList of computer objects. You should have two classes, one called ComputerTest, and the other called Computer. In the ComputerTest class you should: Have a main method which declares an ArrayList of type Computer called computerList, each element of which represents a computer. Initialise the first three entries of the ArrayList Call a static method which prints out the lowest price computer, called lowestPrice The parameter of this method is (i) an ArrayList of type Computer i.e. ArrayList data Sample output: The lowest priced computer is the Cheapo400 at 399 euro. The Computer class should have: Private instance variables: manufacturer, model, price and quality. Quality is a rating from 1 to 10. public get and set methods to retrieve and set/change the value of the four instance variables a default constructor a constructor that takes four parameters

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