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  • What does it mean to say "Instance variables are not over-rided" in java?

    - by Ankit
    I am aware of the concept called field hiding in java. But still I am having a confusion in relation to instance variable being not over-ridden. According to my present knowledge, overriding a method of super-class means that the JVM will call the sub-class's over-ridden method though the super-class's method is available to the sub-class. And I read the similar thing for field hiding via the link:- Hiding Fields So, in any case we are over-ridding the instance if we change the values of the inherited instance variable in the sub-class. I am confused please help. I am using the following super-class:- public class Animal{ File picture; String food; int hunger; int width, height; int xcoord, ycoord; public void makeNoise(){ ......... } public void eat(){ ............. } public void sleep(){ .......... } public void roam(){ ............. } } It has sub-classes like Tiger, cat, dog,hippo etc. The sub-classes over-ride the makeNoise(), eat and roam() method. But each sub-class also uses a different set of values for instance variables. So as per my confusion, I am kind-of overriding all the instance variables and 3 methods of the super-class Animal; and I still have the super-class instance variables available to the sub-class with the use of the super keyword.

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  • Making it look like the computer is thinking in TicTacToe game

    - by rage
    here is a slice of code that i've written in VB.net Private Sub L00_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles L00.Click, L01.Click, L02.Click, L03.Click, L10.Click, L11.Click, L12.Click, L13.Click, L20.Click, L21.Click, L22.Click, L23.Click, L30.Click, L31.Click, L32.Click, L33.Click Dim ticTac As Label = CType(sender, Label) Dim strRow As String Dim strCol As String 'Once a move is made, do not allow user to change whether player/computer goes first, because it doesn't make sense to do so since the game has already started. ComputerFirstStripMenuItem.Enabled = False PlayerFirstToolStripMenuItem.Enabled = False 'Check to make sure clicked tile is a valid tile i.e and empty tile. If (ticTac.Text = String.Empty) Then ticTac.Text = "X" ticTac.ForeColor = ColorDialog1.Color ticTac.Tag = 1 'After the player has made his move it becomes the computers turn. computerTurn(sender, e) Else MessageBox.Show("Please pick an empty tile to make next move", "Invalid Move") End If End Sub Private Sub computerTurn(ByVal sender As System.Object, ByVal e As System.EventArgs) Call Randomize() row = Int(4 * Rnd()) col = Int(4 * Rnd()) 'Check to make sure clicked tile is a valid tile i.e and empty tile. If Not ticTacArray(row, col).Tag = 1 And Not ticTacArray(row, col).Tag = 4 Then ticTacArray(row, col).Text = "O" ticTacArray(row, col).ForeColor = ColorDialog2.Color ticTacArray(row, col).Tag = 4 checkIfGameOver(sender, e) Else 'Some good ole pseudo-recursion(doesn't require a base case(s)). computerTurn(sender, e) End If End Sub Everything works smoothly, except i'm trying to make it seem like the computer has to "think" before making its move. So what i've tried to do is place a System.Threading.Sleep() call in different places in the code above. The problem is that instead of making the computer look like its thinking, the program waits and then puts the X and O together at the same time. Can someone help me make it so that the program puts an X wherever i click AND THEN wait before it places an O? Edit: in case any of you are wondering, i realize that the computers AI is ridiculously dumb, but its just to mess around right now. Later on i will implement a serious AI..hopefully.

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  • sqlite3 'database is locked' won't go away with retries

    - by Azarias
    I have a sqlite3 database that is accessed by a few threads (3-4). I am aware of the general limitations of sqlite3 with regards to concurrency as stated http://www.sqlite.org/faq.html#q6 , but I am convinced that is not the problem. All of the threads both read and write from this database. Whenever I do a write, I have the following construct: try: Cursor.execute(q, params) Connection.commit() except sqlite3.IntegrityError: Notify except sqlite3.OperationalError: print sys.exc_info() print("DATABASE LOCKED; sleeping for 3 seconds and trying again") time.sleep(3) Retry On some runs, I won't even hit this block, but when I do, it never comes out of it (keeps retrying, but I keep getting the 'database is locked' error from exc_info. If I understand the reader/writer lock usage correctly, some amount of waiting should help with the contention. What this sounds like is deadlock, but I do not use any transactions in my code, and every SELECT or INSERT is simply a one off. Some threads, however, keep the same connection when they do their operation (which includes a mix of SELECTS and INSERTS and other modifiers). I would appericiate it if you could shade a light on this, and also ways around fixing it (besides using a different database engine.)

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  • C socket programming: client send() but server select() doesn't see it

    - by Fantastic Fourier
    Hey all, I have a server and a client running on two different machines where the client send()s but the server doesn't seem to receive the message. The server employs select() to monitor sockets for any incoming connections/messages. I can see that when the server accepts a new connection, it updates the fd_set array but always returns 0 despite the client send() messages. The connection is TCP and the machines are separated by like one router so dropping packets are highly unlikely. I have a feeling that it's not select() but perhaps send()/sendto() from client that may be the problem but I'm not sure how to go about localizing the problem area. while(1) { readset = info->read_set; ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); } above is the server side code where the server has a thread that runs select() indefinitely. rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); sleep(3); char * somemsg = "is this working yet?\0"; rv = send(sockfd, somemsg, sizeof(somemsg), NULL); if (rv < 0) printf("MAIN: ERROR send() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); rv = sendto(sockfd, somemsg, sizeof(somemsg), NULL, &server_address, sizeof(server_address)); if (rv < 0) printf("MAIN: ERROR sendto() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); and this is the client side where it connects and sends messages and returns connected MAIN: rv is 4 MAIN: rv is 4 any comments or insightful insights are appreciated.

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  • NSTimer as a timeout mechanism

    - by alexantd
    I'm pretty sure this is really simple, and I'm just missing something obvious. I have an app that needs to download data from a web service for display in a UITableView, and I want to display a UIAlertView if the operation takes more than X seconds to complete. So this is what I've got (simplified for brevity): MyViewController.h @interface MyViewController : UIViewController <UITableViewDelegate, UITableViewDataSource> { NSTimer *timer; } @property (nonatomic, retain) NSTimer *timer; MyViewController.m @implementation MyViewController @synthesize timer; - (void)viewDidLoad { timer = [NSTimer scheduledTimerWithTimeInterval:20 target:self selector:@selector(initializationTimedOut:) userInfo:nil repeats:NO]; [self doSomethingThatTakesALongTime]; [timer invalidate]; } - (void)doSomethingThatTakesALongTime { sleep(30); // for testing only // web service calls etc. go here } - (void)initializationTimedOut:(NSTimer *)theTimer { // show the alert view } My problem is that I'm expecting the [self doSomethingThatTakesALongTime] call to block while the timer keeps counting, and I'm thinking that if it finishes before the timer is done counting down, it will return control of the thread to viewDidLoad where [timer invalidate] will proceed to cancel the timer. Obviously my understanding of how timers/threads work is flawed here because the way the code is written, the timer never goes off. However, if I remove the [timer invalidate], it does.

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  • How can I return the number of rows affected in sqlplus to a shell script?

    - by jessica
    Here is my shell script: # Deletes data from the 'sample' table starting August 30, 2011. # This is done in stages with a 7 second break every # 2 seconds or so to free up the database for other users. # The message "Done." will be printed when there are # no database entries left to delete. user="*****" pass="*****" while(true); do starttime=`date +%s` while [[ $((`date +%s` - $starttime)) -lt 2 ]]; do sqlplus $user/$pass@//blabla <<EOF whenever sqlerror exit 1 delete from sample where sampletime >= to_date('08-30-2011','mm-dd-yyyy') and rownum <= 2; commit; EOF rows = ??? if [ $rows -eq 0 ] ; then echo "Done." exit 0; fi done sleep 7 done If there is no way to get the number of rows, maybe I can use an error code returned by sqlplus to figure out when to end the script? Any thoughts? Thank you!

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  • Check if TIFF file is complete

    - by Davi
    I have a FileSystemWatcher monitoring a directory that receives TIF files from a scanning device. Its necessary to check if the scanning process is done and then read a multipage TIF file, otherwise, the FileSystemWatcher will raise the event before the file be fully scanned. I have something like: private void OnFileCreated(...) { while(IsFileLocked(path)) Thread.Sleep(time); // OK to read } This is what is happening: - Scanner creates the file - FileSystemWatcher detects the file, but its in use - Scanner reads the first page to the file - Scanner releases the file - My code leaves the while(FileInUse(path)) - My code reads the incomplete file (problem) - Scanner adds more pages to the file Let's say the scanner is scanning 100 pages, then, when "OK to read", the file will be incomplete (99 pages left). So, its necessary to know if the file is complete or not. Maybe waiting some time to see if the file is modified, but this time span can be up to hours, because the scanner can get idle scanning the same TIF. Other solution would be checking some flag in the TIF file that indicates that the file is not complete(I've looked for this but don't found anything).

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  • Scala newbie vproducer/consumer attempt running out of memory

    - by Nick
    I am trying to create a producer/consumer type Scala app. The LoopControl just sends a message to the MessageReceiver continually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorActor is associated with an Id. Eventually this is where I want to do business logic. But I run out of memory after 15 minutes. Its finding the cached actors,but quickly runs out of memory. Any help is appreciated. Or any one has any good code on producers consumers doing real stuff (not just adding numbers), please post. import scala.actors.Actor import java.util.HashMap import scala.actors.Actor._ case object LoopControl case object MessageReceiver case object MessageActor case object MessageActorCreator class MessageReceiver(msg: String) extends Actor { var messageActorMap = new HashMap[String, MessageActor] val messageCreatorActor = new MessageActorCreator(null, null) def act() { messageCreatorActor.start loop { react { case MessageActor(messageId) => if (msg.length() > 0) { var messageActor = messageActorMap.get(messageId); if(messageActor == null) { messageCreatorActor ! MessageActorCreator(messageId, messageActorMap) }else { messageActor ! MessageActor } } } } } } case class MessageActorCreator(msg:String, messageActorMap: HashMap[String, MessageActor]) extends Actor { def act() { loop { react { case MessageActorCreator(messageId, messageActorMap) => if(messageId != null ) { var messageActor = new MessageActor(messageId); messageActorMap.put(messageId, messageActor) println(messageActorMap) messageActor.start messageActor ! MessageActor } } } } } class LoopControl(messageReceiver:MessageReceiver) extends Actor { var count : Int = 0; def act() { while (true) { messageReceiver ! MessageActor ("00-122-0X95-FEC0" + count) //Thread.sleep(100) count = count +1; if(count > 5) { count = 0; } } } } case class MessageActor(msg: String) extends Actor { def act() { loop { react { case MessageActor => println() println("MessageActor: Got something-> " + msg) } } } } object messages extends Application { val messageReceiver = new MessageReceiver("bootstrap") val loopControl = new LoopControl(messageReceiver) messageReceiver.start loopControl.start }

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  • Scheduling algorithm optimized to execute during low usage periods.

    - by The Rook
    Lets say there is a Web Application serving mostly one country. Because of normal sleep habits website traffic follows a Sine wave, where 1 period lasts 24 hours and the lowest part of the wave is at about midnight. Is there a scheduling algorithm optimized to execute during low usage periods? I am thinking of this as a liquid that is "pored into" this sine wave to flatten out resource usage. A ideal algorithm would take the integral of this empty space. If the same tasks need to be run daily the amount of resources consumed by previous executions could be used to predict future usage by looking at the rate in which resource usage is increasing. By knowing the amount of resources required this algorithm could fill in this empty space while leaving as much buffer as possible on either side such that its interference was reduced as much as possible. It would also be possible to detect if there isn't enough resources before execution begins, this opens the door for a cloud to help out. Does anything like this exist? Or should I build it into an existing scheduler like quartz and make it open source?

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  • Closing thread using ExitThread - C

    - by Jamie Keeling
    I have a simple program that creates a thread, loops twenty times and then makes a call to close itself and perform the necessary cleanup. When I debug the program it reaches the ExitThread(); method and pauses, ignoring the printf(); I have set up after it to signal to me it's closed. Is this normal or am I forgetting to do something? I'm new to threading using C. Main() void main() { Time t; int i = 0; StartTimer(); for(i = 0; i < 20; i++) { t = GetTime(); printf("%d.%.3d\n", t.seconds, t.milliseconds); Sleep(100); } StopTimer(); } Thread Creation void StartTimer() { DWORD threadId; seconds = 0; milliseconds = 0; // Create child thread hThread = CreateThread( NULL, // lpThreadAttributes (default) 0, // dwStackSize (default) ThreadFunc, // lpStartAddress NULL, // lpParameter 0, // dwCreationFlags &threadId // lpThreadId (returned by function) ); // Check child thread was created successfully if(hThread == NULL) { printf("Error creating thread\n"); } } Thread Close void StopTimer() { DWORD exitCode; if(GetExitCodeThread(hThread,&exitCode) != 0) { ExitThread(exitCode); printf("Thread closed"); if(CloseHandle(hThread)) { printf("Handle closed"); } } }

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  • Checking if a console application is still running using the Process class

    - by Ced
    I'm making an application that will monitor the state of another process and restart it when it stops responding, exits, or throws an error. However, I'm having trouble to make it reliably check if the process (Being a C++ Console window) has stopped responding. My code looks like this: public void monitorserver() { while (true) { server.StartInfo = new ProcessStartInfo(textbox_srcdsexe.Text, startstring); server.Start(); log("server started"); log("Monitor started."); while (server.Responding) { if (server.HasExited) { log("server exitted, Restarting."); break; } log("server is running: " + server.Responding.ToString()); Thread.Sleep(1000); } log("Server stopped responding, terminating.."); try { server.Kill(); } catch (Exception) { } } } The application I'm monitoring is Valve's Source Dedicated Server, running Garry's Mod, and I'm over stressing the physics engine to simulate it stopping responding. However, this never triggers the process class recognizing it as 'stopped responding'. I know there are ways to directly query the source server using their own protocol, but i'd like to keep it simple and universal (So that i can maybe use it for different applications in the future). Any help appreciated

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  • How to enter text into the "Write something..." box on Facebook and click Submit

    - by Peter Payne
    Hello, I am trying to manipulate Facebook pages in various ways, using Javascript browser elements. I'd need to be able to insert some text into the top "Type something..." box that shows on my site's fan page (or alternately, "click into" the field and I can type the text using GUI scripting), then click the "submit" button as if i'd done it by hand. It's tricky since the page is very Ajax heavy and I can't find the names of the elements I need to manipulate, let alone how to manipulate them as they're not using traditional form fields I'm used to. Can anyone help me figure out how to do this with javascript commands, which I'd be calling from Applescript on the Mac? Many thanks in advance. UPDATE Thanks for the comments below. Believe me, I am not trying to do anything spammy or douchy, mainly posting links to products that have gone live on page facebook page, but do it during the business day when people are on rather than at strange hours of the day. I am located in Japan so my sleep period is right when people are using FB. The solution I came up with for clicking the button was got using UI Browser, an outstanding tool if you're trying to script on the Mac. The script that clicked the button for me was: tell application "Safari" activate set thename to name of (get current tab of window 1) delay 3 tell application "System Events" tell process "Safari" try click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 3 of window thename -- this one works on the mini? on error click button "Share" of group 1 of group 2 of list 3 of group 9 of UI element 1 of scroll area 1 of group 2 of window thename -- did not work end try end tell end tell end tell Hope this is useful to anyone.

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  • How can I remove a JPanel from a JFrame?

    - by Roman
    Recently I asked here how to add a new JPanel to JFrame. The answer helped me to get a working code. But not I have a related question: "How can I remove an old JPanel". I need that because of the following problem. A new JPanel appears appears when I want (either time limit is exceeded or user press the "Submit" button). But in several seconds some element of the old JPanel appears together with the component of the new JPanel. I do not understand why it happens. I thought that it is because I have to other threads which update the window. But the first thread just add the old panel once (so, it should be finished). And in the second thread I have a loop which is broken (so, it also should be finished). Here is my code: private Thread controller = new Thread() { public void run() { // First we set the initial pane (for the selection of partner). SwingUtilities.invokeLater(new Runnable() { public void run() { frame.getContentPane().add(generatePartnerSelectionPanel()); frame.invalidate(); frame.validate(); } }); // Update the pane for the selection of the parnter. for (int i=40; i>0; i=i-1) { final int sec = i; SwingUtilities.invokeLater(new Runnable() { public void run() { timeLeftLabel.setText(sec + " seconds left."); } }); try {Thread.sleep(1000);} catch (InterruptedException e) {} if (partnerSubmitted) {break;} } // For the given user the selection phase is finished (either the time is over or form was submitted). SwingUtilities.invokeLater(new Runnable() { public void run() { frame.getContentPane().add(generateWaitForGamePanel()); frame.invalidate(); frame.validate(); } }); } };

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  • using a While loop to control the value of a keyframe in a timeline in Javafx

    - by dragoknight
    i want to create an animation where the ball will move in one of the 4 sectors of a circle randomly.this will happen 5 times.so,i create a while loop(i<5) and call the random function.i then create an if loop and attach some x and y values according to the random fn value.i then create an timeline object inside the while loop and in the key frame value,i use these x and y values.but when i run the program,what happens is that all the values are being created(x and y values seen through println) but only the last x and y value(for i=5)is being rendered in the screen.the animations for the previous values(1<=i<=4)are not being rendered.Please advise where have i gone wrong? public function run(args:String[]) { var i=0; while(i<5) { var z=gety(); println(z); // var relativeTime:Duration=0s; if(z==1) {xbind=120; ybind=80; } else if(z==2) {xbind=120; ybind=120; } else if(z==3) { xbind=80; ybind=120; } else if(z==4) { xbind=80; ybind=80; } var t:Timeline=Timeline{ //time: bind pos with inverse; repeatCount: Timeline.INDEFINITE autoReverse: true keyFrames: [ KeyFrame{ time: 0s values: [ x => 100.0,y => 100.0]}, KeyFrame{time: 2s values:[x => xbind tween Interpolator.LINEAR, y => ybind tween Interpolator.LINEAR,] }, ] }//end timeline i++; t.play(); Thread.sleep(2000); }//end while }

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  • What is an efficient strategy for multiple threads posting jobs and waiting for response from a single thread?

    - by jakewins
    In java, what is an efficient solution to the following problem: I have multiple threads (10-20 or so) generating jobs ("Job Creators"), and a single thread capable of performing them ("The worker"). Once a job creator has posted a job, it should wait for the job to finish, yielding no result other than "it's done", before it keeps going. For sending the jobs to the worker thread, I think a ring buffer or similar standard fan-in setup would perhaps be a good approach? But for a Job Creator to find out that her job has been done, I'm not so sure.. The job creators could sleep, and the worker interrupt them when done.. Or each job creator could have an atomic boolean that it checks, and that the worker sets. I dunno, neither of those feel very nice. I'd like to do it with as few (none, if possible) locks as absolutely possible. So to be clear: What I'm looking for is speed, not necessarily simplicity. Does anyone have any suggestions? Links to reading about concurrency strategies would also be very welcome!

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  • Can an application affect TCP retransmits

    - by sipwiz
    I'm troubleshooting some communications issues and in the network traces I am occasionally coming across TCP sequence errors. One example I've got is: Server to Client: Seq=3174, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3224, Len=50 Client to Server: Ack=3224 Server to Client: Seq=3274, Len=10 Client to Server: Ack=3224, SLE=3274, SRE=3284 Packets 4 & 5 are recorded in the trace (which is from a router in between the client and server) at almost exactly the same time so they most likely crossed in transit. The TCP session has got out of sync with the client missing the last two transmissions from the server. Those two packets should have been retransmitted but they weren't, the next log in the trace is a RST packet from the Client 24 seconds after packet 6. My question is related to what could be responsible for the failure to retransmit the server data from packets 3 & 5? I would assume that the retransmit would be at the operating system level but is there anyway the application could influence it and stop it being sent? A thread blocking or put to sleep or something like that?

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  • Using shared_ptr to implement RCU (read-copy-update)?

    - by yongsun
    I'm very interested in the user-space RCU (read-copy-update), and trying to simulate one via tr1::shared_ptr, here is the code, while I'm really a newbie in concurrent programming, would some experts help me to review? The basic idea is, reader calls get_reading_copy() to gain the pointer of current protected data (let's say it's generation one, or G1). writer calls get_updating_copy() to gain a copy of the G1 (let's say it's G2), and only one writer is allowed to enter the critical section. After the updating is done, writer calls update() to do a swap, and make the m_data_ptr pointing to data G2. The ongoing readers and the writer now hold the shared_ptr of G1, and either a reader or a writer will eventually deallocate the G1 data. Any new readers would get the pointer to G2, and a new writer would get the copy of G2 (let's say G3). It's possible the G1 is not released yet, so multiple generations of data my co-exists. template <typename T> class rcu_protected { public: typedef T type; typedef std::tr1::shared_ptr<type> rcu_pointer; rcu_protected() : m_data_ptr (new type()) {} rcu_pointer get_reading_copy () { spin_until_eq (m_is_swapping, 0); return m_data_ptr; } rcu_pointer get_updating_copy () { spin_until_eq (m_is_swapping, 0); while (!CAS (m_is_writing, 0, 1)) {/* do sleep for back-off when exceeding maximum retry times */} rcu_pointer new_data_ptr(new type(*m_data_ptr)); // as spin_until_eq does not have memory barrier protection, // we need to place a read barrier to protect the loading of // new_data_ptr not to be re-ordered before its construction _ReadBarrier(); return new_data_ptr; } void update (rcu_pointer new_data_ptr) { while (!CAS (m_is_swapping, 0, 1)) {} m_data_ptr.swap (new_data_ptr); // as spin_until_eq does not have memory barrier protection, // we need to place a write barrier to protect the assignments of // m_is_writing/m_is_swapping be re-ordered bofore the swapping _WriteBarrier(); m_is_writing = 0; m_is_swapping = 0; } private: volatile long m_is_writing; volatile long m_is_swapping; rcu_pointer m_data_ptr; };

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  • For loop index out of range ArgumentOutOfRangeException when multithreading

    - by Lirik
    I'm getting some strange behavior... when I iterate over the dummyText List in the ThreadTest method I get an index out of range exception (ArgumentOutOfRangeException), but if I remove the threads and I just print out the text, then everything works fine. This is my main method: public static Object sync = new Object(); static void Main(string[] args) { ThreadTest(); Console.WriteLine("Press any key to continue."); Console.ReadKey(); } This method throws the exception: private static void ThreadTest() { Console.WriteLine("Running ThreadTest"); Console.WriteLine("Running ThreadTest"); List<String> dummyText = new List<string>() { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"}; for (int i = 0; i < dummyText.Count; i++) { Thread t = new Thread(() => PrintThreadName(dummyText[i])); // <-- Index out of range?!? t.Name = ("Thread " + (i)); t.IsBackground = true; t.Start(); } } private static void PrintThreadName(String text) { Random rand = new Random(DateTime.Now.Millisecond); while (true) { lock (sync) { Console.WriteLine(Thread.CurrentThread.Name + " running " + text); Thread.Sleep(1000+rand.Next(0,2000)); } } } This does not throw the exception: private static void ThreadTest() { Console.WriteLine("Running ThreadTest"); List<String> dummyText = new List<string>() { "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"}; for (int i = 0; i < dummyText.Count; i++) { Console.WriteLine(dummyText[i]); // <-- No exception here } } Does anybody know why this is happening?

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  • PHP curl timing mismatch

    - by JonoB
    I am running a php script that: queries a local database to retrieve an amount executes a curl statement to update an external database with the above amount + x queries the local database again to insert a new row reflecting that the curl statement has been executed. One of the problems that I am having is that the curl statement takes 2-4 seconds to execute, so I have two different users from the same company running the same script at the same time, the execution time of the curl command can cause a mismatch in what should be updated in the external database. This is the because the curl statement has not yet returned from the first user...so the second user is working off incorrect figures. I am not sure of the best options here, but basically I need to prevent two or more curl statements being run at the same time. I thought of storing a value in the database that indicates that the curl statement is being executed at that time, and prevent any other curl statements being run until its completed. Once the first curl statement has been executed, then the database flag is updated and the next one can run. If this field is 'locked', then I could loop through the code and sleep for (5) seconds, and then check again if the flag has been reset. If after (3) loops, then reset the flag automatically (i've never seen the curl take longer than 5 seconds) and continue processing. Are there any other (more elegant) ways of approaching this?

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  • Strange problem with simple multithreading program in Java

    - by Elizabeth
    Hello, I am just starting play with multithreading programming. I would like to my program show alternately character '-' and '+' but it doesn't. My task is to use synchronized keyword. As far I have: class FunnyStringGenerator{ private char c; public FunnyStringGenerator(){ c = '-'; } public synchronized char next(){ if(c == '-'){ c = '+'; } else{ c = '-'; } return c; } } class ThreadToGenerateStr implements Runnable{ FunnyStringGenerator gen; public ThreadToGenerateStr(FunnyStringGenerator fsg){ gen = fsg; } @Override public void run() { for(int i = 0; i < 10; i++){ System.out.print(gen.next()); } } } public class Main{ public static void main(String[] args) throws IOException { FunnyStringGenerator FSG = new FunnyStringGenerator(); ExecutorService exec = Executors.newCachedThreadPool(); for(int i = 0; i < 20; i++){ exec.execute(new ThreadToGenerateStr(FSG)); } } } EDIT: I also testing Thread.sleep in run method instead for loop.

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  • SWT Problem with MouseTrackListener and Shell

    - by Krt_Malta
    Hi! I'm developing an Eclipse plug-in and I have a problem which is reproduced in this small SWT application: public static void main(String[] args) { Display display = new Display(); Shell shell = new Shell(display); Text text = new Text(shell, SWT.MULTI | SWT.WRAP | SWT.READ_ONLY | SWT.V_SCROLL); text.setText("Hello"); shell.setLayout(new FillLayout()); shell.addMouseTrackListener(new MouseTrackListener() { public void mouseEnter(MouseEvent arg0) { System.out.println("mouseEnter"); } public void mouseExit(MouseEvent arg0) { System.out.println("mouseExit"); } public void mouseHover(MouseEvent arg0) { System.out.println("mouseHover"); } }); // Display the window shell.open(); while (!shell.isDisposed()) { if (!display.readAndDispatch()) { display.sleep(); } } display.dispose(); } As you can see I'm creating a shell and putting a Textbox inside it and putting it all across the shell. Then I attach a MouseTrackListener to the shell. The events don't fire (as in when I hover in the shell "mouseHover" is not printed etc). When I remove the Textbox the events fire. Can anyone tell me where the problem lies please? I don't want to attach a listener to the textbox but to the shell. I'll really appreciate the help because I've been trying to trace it for quite some time now. Thanks and regards, Krt_Malta

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  • TransactionRequiredException on OptimisticLockException

    - by João Madureira Pires
    Hi there. I have the following class that generates sequencial Card Numbers. I'm trying to recover from OptimisticLockException, by calling recursively the same method. however, i'm getting TransactionRequiredException. Dows anyone knows how to recover from OptimisticLockException in my case? Thanks a lot in advance @Name("simpleAutoIncrementGenerator") public class SimpleAutoIncrementGenerator extends CardNumberGenerator{ private static final long serialVersionUID = 2869548248468809665L; private int numberOfRetries = 0; @Override public String generateNextNumber(CardInstance cardInstance, EntityManager entityManager) { try{ EntityCard card = (EntityCard)entityManager.find(EntityCard.class, cardInstance.getId()); if(card != null){ String nextNumber = ""; String currentNumber = card.getCurrentCardNumber(); if(currentNumber != null && !currentNumber.isEmpty()){ Long numberToInc = Long.parseLong(currentNumber); numberToInc ++; nextNumber = String.valueOf(numberToInc); card.setCurrentCardNumber(nextNumber); // this is just to cause a OptimisticLock Exception try { Thread.sleep(4000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } entityManager.persist(card); entityManager.flush(); return nextNumber; } } }catch (OptimisticLockException oLE) { System.out.println("\n\n\n\n OptimisticLockException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } }catch (TransactionRequiredException trE) { System.out.println("\n\n\n\n TransactionRequiredException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } }catch (StaleObjectStateException e) { System.out.println("\n\n\n\n StaleObjectStateException \n\n\n\n"); if(numberOfRetries < CentralizedConfig.CARD_NUMBER_GENERATOR_MAX_TRIES){ numberOfRetries ++; return generateNextNumber(cardInstance,entityManager); } } return null; } }

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  • Run a command as cron would but from the command line.

    - by BCS
    I have a script that I'm trying to run from cron. When I run it from bash, it work just fine. However when I let cron do it's thing, I get a: myscript.sh: line 122: syntax error: unexpected end of file What I want is a way to run a command as if it was a cron job, but do it in my shell. As a side note: does anyone know what would be differnt under cron? (the script already has a #!/bin/sh line) To answer my own question: I added this to my crontab: * * * * * bcs for ((i=1; i <= 55; i++)) ; do find ~/.crontemp/ -name '*.run' -exec "{}" ";" ; sleep 1; done` and created this script: #!/bin/sh tmp=$(mktemp ~/.crontemp/cron.XXXXX) mknod $tmp.pipe p mv $tmp $tmp.pre echo $* '>' $tmp.pipe '1>&2' >> $tmp.pre echo rm $tmp.run >> $tmp.pre chmod 700 $tmp.pre mv $tmp.pre $tmp.run cat $tmp.pipe rm $tmp.pipe With that, I can run an arbitrary command with a delay of not more than one second. (And yes, I know there are all kinds of security issue involved in that)

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  • Pymedia video encoding failed

    - by user1474837
    I am using Python 2.5 with Windows XP. I am trying to make a list of pygame images into a video file using this function. I found the function on the internet and edited it. It worked at first, than it stopped working. This is what it printed out: Making video... Formating 114 Frames... starting loop making encoder Frame 1 process 1 Frame 1 process 2 Frame 1 process 2.5 This is the error: Traceback (most recent call last): File "ScreenCapture.py", line 202, in <module> makeVideoUpdated(record_files, video_file) File "ScreenCapture.py", line 151, in makeVideoUpdated d = enc.encode(da) pymedia.video.vcodec.VCodecError: Failed to encode frame( error code is 0 ) This is my code: def makeVideoUpdated(files, outFile, outCodec='mpeg1video', info1=0.1): fw = open(outFile, 'wb') if (fw == None) : print "Cannot open file " + outFile return if outCodec == 'mpeg1video' : bitrate= 2700000 else: bitrate= 9800000 start = time.time() enc = None frame = 1 print "Formating "+str(len(files))+" Frames..." print "starting loop" for img in files: if enc == None: print "making encoder" params= {'type': 0, 'gop_size': 12, 'frame_rate_base': 125, 'max_b_frames': 90, 'height': img.get_height(), 'width': img.get_width(), 'frame_rate': 90, 'deinterlace': 0, 'bitrate': bitrate, 'id': vcodec.getCodecID(outCodec) } enc = vcodec.Encoder(params) # Create VFrame print "Frame "+str(frame)+" process 1" bmpFrame= vcodec.VFrame(vcodec.formats.PIX_FMT_RGB24, img.get_size(), # Covert image to 24bit RGB (pygame.image.tostring(img, "RGB"), None, None) ) print "Frame "+str(frame)+" process 2" # Convert to YUV, then codec da = bmpFrame.convert(vcodec.formats.PIX_FMT_YUV420P) print "Frame "+str(frame)+" process 2.5" d = enc.encode(da) #THIS IS WHERE IT STOPS print "Frame "+str(frame)+" process 3" fw.write(d.data) print "Frame "+str(frame)+" process 4" frame += 1 print "savng file" fw.close() Could somebody tell me why I have this error and possibly how to fix it? The files argument is a list of pygame images, outFile is a path, outCodec is default, and info1 is not used anymore. UPDATE 1 This is the code I used to make that list of pygame images. from PIL import ImageGrab import time, pygame pygame.init() f = [] #This is the list that contains the images fps = 1 for n in range(1, 100): info = ImageGrab.grab() size = info.size mode = info.mode data = info.tostring() info = pygame.image.fromstring(data, size, mode) f.append(info) time.sleep(fps)

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  • static variable lose its value

    - by user542719
    I have helper class with this static variable that is used for passing data between two classes. public class Helper{ public static String paramDriveMod;//this is the static variable in first calss } this variable is used in following second class mathod public void USB_HandleMessage(char []USB_RXBuffer){ int type=USB_RXBuffer[2]; MESSAGES ms=MESSAGES.values()[type]; switch(ms) { case READ_PARAMETER_VALUE: // read parameter values switch(prm){ case PARAMETER_DRIVE_MODE: // paramet drive mode Helper.paramDriveMod =(Integer.toString(((USB_RXBuffer[4]<< 8)&0xff00))); System.out.println(Helper.paramDriveMod+"drive mode is selectd ");//here it shows the value that I need. ..........}}//let say end switch and method and the following is an third class method use the above class method public void buttonSwitch(int value) throws InterruptedException{ boolean bool=true; int c=0; int delay=(int) Math.random(); while(bool){ int param=3; PARAMETERS prm=PARAMETERS.values()[param]; switch(value){ case 0: value=1; while(c<5){ Thread.sleep(delay); protocol.onSending(3,prm.PARAMETER_DRIVE_MODE.ordinal(),dataToRead,dataToRead.length);//read drive mode System.out.println(Helper.paramDriveMod+" drive mode is ..........in wile loop");//here it shows null value }}//let say end switch and method what is the reason that this variable lose its value?

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