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  • Total Order between !different! volatile variables?

    - by andreas
    Hi all, Consider the following Java code: volatile boolean v1 = false; volatile boolean v2 = false; //Thread A v1 = true; if (v2) System.out.println("v2 was true"); //Thread B v2 = true; if (v1) System.out.println("v1 was true"); If there was a globally visible total order for volatile accesses then at least one println would always be reached. Is that actually guaranteed by the Java Standard? Or is an execution like this possible: A: v1 = true; B: v2 = true; A: read v2 = false; B: read v1 = false; A: v2 = true becomes visible (after the if) B: v1 = true becomes visible (after the if) I could only find statements about accesses to the same volatile variable in the Standard (but I might be missing something). "A write to a volatile variable (§8.3.1.4) v synchronizes-with all subsequent reads of v by any thread (where subsequent is defined according to the synchronization order)." http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.4.4 Thanks!

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  • Monitor.Wait, Pulse - When worker thread should conditionally behave as an actual worker thread

    - by Griever
    My particular scenario: - Main thread starts a worker thread. - Main thread needs to block itself until either worker thread is completed (yeah funny) or worker thread itself informs main thread to go on Alright, so what I did in main thread: wokerThread.Start(lockObj); lock(lockObj) Monitor.Wait(lockObj); Somewhere in worker thread: if(mainThreadShouldGoOn) lock(lockObj) Monitor.Pulse(lockObj); Also, at the end of worker thread: lock(lockObj) Monitor.Pulse(lockObj); So far, it's working perfect. But is it a good solution? Is there a better one?

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  • Pause and resume thread drawing to SurfaceView

    - by fhucho
    I am developing a chess game for Android (http://androidchess.appspot.com), using SurfaceView for the chessboard. I have a drawing Thread, that draws the chessboard in a loop. The problem is that when there are no active animations (this is more that 90% of time), it makes no sense to waste CPU and battery for drawing. How should I solve this? Maybe somehow pausing and resuming the drawing Thread?

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  • How do I update blackberry UI items from a thread?

    - by Andrei T. Ursan
    public class PlayText extends Thread { private int duration; private String text; private PlayerScreen playerscrn; public PlayText(String text, int duration) { this.duration = duration; this.text = text; this.playerscrn = (PlayerScreen)UiApplication.getUiApplication().getActiveScreen(); } public void run() { synchronized(UiApplication.getEventLock()) { try{ RichTextField text1player = new RichTextField(this.text, Field.NON_FOCUSABLE); playerscrn.add(text1player); playerscrn.invalidate(); Thread.sleep(this.duration); RichTextField text2player = new RichTextField("hahhaha", Field.NON_FOCUSABLE); playerscrn.add(text2player); playerscrn.invalidate(); Thread.sleep(1000); RichTextField text3player = new RichTextField("Done", Field.NON_FOCUSABLE); playerscrn.add(text3player); playerscrn.invalidate(); }catch(Exception e){ System.out.println("I HAVE AN ERROR"); } } } } With the above code I'm trying to create a small text player. Instead to get all the text labels one by one, something like display text1player wait this.duration milliseconds display text2player wait 1000 milliseconds display text3player thread done. The screens waits this.duration + 1000 milliseconds and displays all the labels at once. I tried with a runnable and calling .invokeLater or .invokeAndWait but I still get the same behavior, and even if I get dirty like above using synchronized it still doesn't work. Does anyone know how I can display each label at a time? Thank you!

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  • Stream writing lags my GUI

    - by blez
    I have a thread that dequeues data from a queue and write it to another application's STDIN. I'm using Stream, but with .Write and even .BeginWrite, when I send 1mb chunks to the second app, my GUI gets laggy for ~1sec. Why?

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  • Start thread with two parameters

    - by Matt
    I've got a method that gets called on an event, which presents me with two variables varA, varB (both strings). This method gets called with new information quite frequently, thus I have created a separate method that takes in the two parameters. I want to run this method in a thread, however have struck the issue that Thread.Start will not accept parameters. I've tried a few supposed methods, but have so far had no luck.. I think my best bet is to create a separate class, and handle it there.. However I have a List which I am inserting data into, and hit a dead end when the separate class tried to access that list, since it was in a different class. Can someone help me out here please?

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  • How the simples GUI countdown is supposed to work?

    - by Roman
    I am trying to write the simples GUI countdown. I found in Internet some code but it is already too fancy for me. I am trying to keep it as simple as possible. So, I just want to have a window saying "You have 10 second left". The number of second should decrease every second from 10 to 0. I wrote a code. And I think I am close to the working solution. But I still missing something. Could you pleas help me to find out what is wrong? Here is my code: import javax.swing.*; public class Countdown { static JLabel label; // Method which defines the appearance of the window. private static void showGUI() { JFrame frame = new JFrame("Simple Countdown"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JLabel label = new JLabel("Some Text"); frame.add(label); frame.pack(); frame.setVisible(true); } // Define a new thread in which the countdown is counting down. static Thread counter = new Thread() { public void run() { for (int i=10; i>0; i=i-1) { updateGUI(i,label); try {Thread.sleep(1000);} catch(InterruptedException e) {}; } } }; // A method which updates GUI (sets a new value of JLabel). private static void updateGUI(final int i, final JLabel label) { SwingUtilities.invokeLater(new Runnable(i,label) { public Runnable(int i, JLabel label) { this.i = i; this.label = label; } public void run() { label.setText("You have " + i + " seconds."); } }); } // The main method (entry point). public static void main(String[] args) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { showGUI(); //counter.start(); } }); //counter.start(); } } And I have several concrete question about this code: Where should I place the counter.start();? (In my code I put it on 2 places. Which one is correct?) Why compiler complains about the constructor for Runnable? It says that I have an invalid method declaration and I need to specify the returned type. ADDED: I made the suggested corrections. And then I execute the code and get: Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at Worker.run(Worker.java:12) In the Worker.java in the line 12 I have: label.setText("You have " + i + " seconds.");.

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  • java.util.concurrent.ThreadPoolExecutor strange logic

    - by rodrigoap
    Look ath this method of ThreadPoolExcecutor: public void execute(Runnable command) { ... if (runState == RUNNING && workQueue.offer(command)) { if (runState != RUNNING || poolSize == 0) ensureQueuedTaskHandled(command); } ... } It check that runState is RUNNING and then the oposite. As I'm trying to do some tuning on a SEDA like model I wanted to understand the internals of the thread pool. Do you think this code is correct?

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  • Why reduce the size of the Java JVM thread stack?

    - by djangofan
    I was reading an article on handling Out Of Memory error conditions in Java (and on JBoss platform) and I saw this suggestion to reduce the size of the threadstack. Can anyone explain how "reducing" the size of threadstack will help with a max memory error condition? http://community.jboss.org/wiki/OutOfMemoryExceptions

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  • Why .NET does not allow cross-thread operations?

    - by RHaguiuda
    This question is not about what is a cross-thread operation, and how to avoid it, but why internal mechanics of .NET framework does not allow a cross-thread operation. I can`t understand why a SerialPort DataReceived event cannot update a simple text box on my form and why using delegates this is possible?

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  • Understanding Thread/BeginInvoke? [beginner]

    - by Moberg
    Consider the code: class Work { public void DoStuff(string s) { Console.WriteLine(s); // .. whatever } } class Master { private readonly Work work = new Work(); public void Execute() { string hello = "hello"; // (1) is this an ugly hack ? var thread1 = new Thread(new ParameterizedThreadStart(o => this.work.DoStuff((string)o))); thread1.Start(hello); thread1.Join(); // (2) is this similar to the one above? new Action<string>(s => this.work.DoStuff(s)).BeginInvoke(hello, null, null); } } Is (1) an acceptable way of easy starting some work in a seperate thread? If not a better alternative would be much appreciated. Is (2) doing the same? I guess what I ask is if a new thread is started, or.. Hope you can help a beginner to a better understanding :) /Moberg

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  • Can't resolve CalledFromWrongThreadException with Handler

    - by michel
    I will try to keep it simple: In my main activity I make a handler: public class ARViewer extends ARDisplayActivity { public final MHandler mHandler = new MHandler(this); public void onCreate(Bundle savedInstanceState) { ... The class MHandler: public final class MHandler extends Handler{ //main activity private ARViewer arnv; public MHandler(ARViewer arnv){ this.arnv = arnv; } @Override public void handleMessage(Message msg) { ... case H_RR : arnv.setContentView(R.layout.routeplanner); break; ... super.handleMessage(msg); } } But if I call the handleMessage method from a callback function in a other Class, definitely from a other thread, I still get the exception message: CalledFromWrongThreadException (Only the original thread that created a view hierarchy can touch its views) : public void rFound(Route route) { Message msg = new Message(); msg.what = MHandler.H_RR; ARViewer.arnv.mHandler.handleMessage(msg); }

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  • How to check whether the form has any ShowDialog() forms open?

    - by kornelijepetak
    I have a form MainForm with several properties/methods that are accessed from another thread. At some point I might open a form AuxForm with ShowDialog() and then while that modal form is open, the other thread still modifies the MainForm's properties. This is all desired. In one of the methods accessed from another thread I need to execute some code, but only if the modal AuxForm is not open. Is there any way to check this (by using .NET WF Form properties) or I need to use a flag variable? NOTE: None of these properties/methods modify the controls (so no Invoke is required).

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  • How do you pass a BitmapImage from a background thread to the UI thread in WPF?

    - by DanM
    I have a background thread that generates a series of BitmapImage objects. Each time the background thread finishes generating a bitmap, I would like to show this bitmap to the user. The problem is figuring out how to pass the BitmapImage from the background thread to the UI thread. This is an MVVM project, so my view has an Image element: <Image Source="{Binding GeneratedImage}" /> My view-model has a property GeneratedImage: private BitmapImage _generatedImage; public BitmapImage GeneratedImage { get { return _generatedImage; } set { if (value == _generatedImage) return; _generatedImage= value; RaisePropertyChanged("GeneratedImage"); } } My view-model also has the code that creates the background thread: public void InitiateGenerateImages(List<Coordinate> coordinates) { ThreadStart generatorThreadStarter = delegate { GenerateImages(coordinates); }; var generatorThread = new Thread(generatorThreadStarter); generatorThread.ApartmentState = ApartmentState.STA; generatorThread.IsBackground = true; generatorThread.Start(); } private void GenerateImages(List<Coordinate> coordinates) { foreach (var coordinate in coordinates) { var backgroundThreadImage = GenerateImage(coordinate); // I'm stuck here...how do I pass this to the UI thread? } } I'd like to somehow pass backgroundThreadImage to the UI thread, where it will become uiThreadImage, then set GeneratedImage = uiThreadImage so the view can update. I've looked at some examples dealing with the WPF Dispatcher, but I can't seem to come up with an example that addresses this issue. Please advise.

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  • If terminating a hung thread is a good idea, how do I do it safely?

    - by Steve
    My Delphi program relies heavily on Outlook automation. Outlook versions prior to 2007-SP2 tend to get stuck in memory due to badly written addins and badly written Outlook code. If Outlook is stuck, calling CreateOleObject('Outlook.Application') or GetActiveObject ... doesn't return and keeps my application hanging till Outlook.exe is closed in the task manager. I've thought of a solution, but I'm unsure whether it's good practice or not. I'd start Outlook with CreateOleObject in a separate thread, wait 10 seconds in my main thread and if Outlook hangs (CreateOleObject doesn't return), offer the user to kill the Outlook.exe process from my program. But since I don't want to force the user to kill the Outlook.exe process, as an alternative I also need a way to kill the new thread in my program which keeps hanging now. Is this good practice? How can I terminate a hanging thread in Delphi without leaking memory?

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  • WCF Service method syncronous/async

    - by Rafal
    Hi I have a problem withi calling WCF Service methods vs Silverlight 3. ` private bool usr_OK = false; clientService.CheckUserMailAsync(this.mailTF.Text); if (usr_OK == true) { isValidationOK = true; } else { isValidationOK = false; MessageBox.Show("User already exists.", "User registered succes!", MessageBoxButton.OK); } ` CheckUserMail should change usr_OK parameter. However it runs in other thread and it does not change the usr_OK param before IF block begins. I've tried thread.join byt the application freezed and i do not know what to do else. Please help me...how can i wait for WCF method to return param usr_OK.

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  • What is the best way, if possible, to send information from a Java PrintStream to a JTextPane?

    - by Daniel Reeves
    In Java, I have a package that translates XML metadata from one standard to another. This package is ultimately accessed through a single function and sends all of its output through a PrintStream object. The output sent is just a status of each file and whether or not it was translated. This is pretty fine and dandy if I'm just printing to System.out, but I'm actually wanting to print this to a JTextPane while it translates (kind of like a progress text box). It wouldn't be a big deal to just print the status after it was done translating the XML, but since there may be thousands of XML files, that's just not feasible. One thing that I've tried is to use a thread that takes all of the information from the PrintStream (which is attached to a ByteArrayOutputStream) and let it send any new information to the text pane. Unfortunately, this still sends the information all at once at the end of the translation. This does work correctly for System.out. Here's the code that does the translation and tries to show the output: public class ConverterGUI extends javax.swing.JFrame { boolean printToResultsBox = false; PrintStream printStream = null; ByteArrayOutputStream baos = null; private class ResultsPrinter implements Runnable { public ResultsPrinter() { baos = new ByteArrayOutputStream(); printStream = new PrintStream(baos); } public void run() { String tempString = ""; while (printToResultsBox) { try { if (!baos.toString().equals(tempString)) { tempString = baos.toString(); resultsBox.setText(tempString); } } catch (Exception ex) { } } } } ... ResultsPrinter rp = new ResultsPrinter(); Thread thread = new Thread(rp); thread.start(); // Do the translation. try { printToResultsBox = true; boolean success = false; TranslationEngine te = new TranslationEngine(); // fileOrFolderToConvert is a text box in the GUI. // linkNeeded and destinationFile are just parameters for the translation process. success = te.translate(fileOrFolderToConvert.getText(), linkNeeded, destinationFile, printStream); if (success) { printStream.println("File/folder translation was a success."); } resultsBox.setText(baos.toString()); } catch (Exception ex) { printStream.println("File translation failed."); } finally { printToResultsBox = false; } ... } Ultimately, this code prints out to the JTextPane just fine after all the translation is done but not during. Any suggestions? Do I need to change the PrintStream to something else?

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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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  • Update JProgressBar from new Thread

    - by Dacto
    How can I update the JProgressBar.setValue(int) from another thread? My secondary goal is do it in the least amount of classes possible. Here is the code I have right now: **Part of the main class....** pp.addActionListener( new ActionListener(){ public void actionPerformed(ActionEvent event) { new Thread(new Task(sd.getValue())).start(); } }); public class Task implements Runnable{ int val; public Task(int value){ this.val = value; } @Override public void run() { for (int i=0; i<=value; i++){ //Progressively increment variable i pbar.setValue(i); //Set value pbar.repaint(); //Refresh graphics try{Thread.sleep(50);} //Sleep 50 milliseconds catch (InterruptedException err){} } } } pp is a JButton and starts the new thread when the JButton is clicked. pbar is the JProgressBar object from the Main class. How can I update its value?(progress) The code above in run() cannot see the pbar.

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