Atomic block of code in SwingWorker thread?

Hi,
I am coding a Swing application. It has a SwingWorker thread that can be interrupted by a Progress bar.
Inside the worker thread, there are a few lines of code (not a method) that should be executed all or none. In another word,
if the thread runs in the middle of this block, the thread must finish this block. How can this be accomplished? This block of code has nothing to do with database read/write. The reason for the block of code being atomic is that I need to make sure of data consistency. There are no other thread except for
the main thread(event-dispatch thread) and the worker thread.
Thanks a lot!
David

You need to synchronize your atomic block and the code to interrupt the thread on the same object.

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Is SwingWorker Thread Cancellation Cooperative?

Hello,
Would appreciate any help in understanding this. My understanding is that cancellation of a SwingWorker thread is cooperative. However, that isn't what I'm seeing.
I have code below that will stop the SwingWorker thread even though I have no operations that are interruptable. Note for the test that I have specifically put an infinite loop in doStuff().   When I do the cancellation in the main() routine: worker.cancel(true), I end up in the done() function indicating that doInBackground() exited. It looks like the thread is being killed even in the absence of an interruptable operation. Note if I change to worker.cancel(false), I get the same effect.
class AWorker extends SwingWorker<String, Object> {
void doStuff() {'
System.out.println("Entered doStuff");
    while (true);
@Override
public String doInBackground() {
    //System.out.println("doInBackground started");
    doStuff();
    return "hello";
@Override
protected void done() {
    try {
      System.out.println("done() entered");
      String status = get();
      System.out.println("done(): get = " + status);
    } catch (Exception e) {
      System.out.println("done(): Exception: " + e);
public class InterruptThread {
public static void main(String[] args) throws Exception {
    AWorker worker = new AWorker();
    worker.execute();
    Thread.sleep(5000);
    worker.cancel(true);

Hello,
Would appreciate any help in understanding this. My understanding is that cancellation of a SwingWorker thread is cooperative. However, that isn't what I'm seeing.
I have code below that will stop the SwingWorker thread even though I have no operations that are interruptable. Note for the test that I have specifically put an infinite loop in doStuff().   When I do the cancellation in the main() routine: worker.cancel(true), I end up in the done() function indicating that doInBackground() exited. It looks like the thread is being killed even in the absence of an interruptable operation. Note if I change to worker.cancel(false), I get the same effect.
class AWorker extends SwingWorker<String, Object> {
void doStuff() {'
System.out.println("Entered doStuff");
    while (true);
@Override
public String doInBackground() {
    //System.out.println("doInBackground started");
    doStuff();
    return "hello";
@Override
protected void done() {
    try {
      System.out.println("done() entered");
      String status = get();
      System.out.println("done(): get = " + status);
    } catch (Exception e) {
      System.out.println("done(): Exception: " + e);
public class InterruptThread {
public static void main(String[] args) throws Exception {
    AWorker worker = new AWorker();
    worker.execute();
    Thread.sleep(5000);
    worker.cancel(true);

[Problem reading a file in a static block of code]

Hi all,
I'm trying to use a static block of code in an abstract class (let's say for initialisation). In this block I'm trying to read some lines of text from a file, and some FileNotFoundException are thrown,
java.io.FileNotFoundException: file:/home/tom/workspace/cryptanalysis/data/keys (No such file or directory)
java.io.FileNotFoundException: file:/home/tom/workspace/cryptanalysis/data/french_words (No such file or directory)
but all the paths are valid and the files exist as you can see:
tom@javahouse ~ $ ll /home/tom/workspace/cryptanalysis/data/
total 24K
-rw-r--r-- 1 tom users 151 jan 3 23:26 french_frequences
-rw-r--r-- 1 tom users 2,0K jan 4 17:21 french_texts
-rw-r--r-- 1 tom users 11K jan 4 17:16 french_words
-rw-r--r-- 1 tom users 159 jan 4 17:21 keys
tom@javahouse ~ $ cat /home/tom/workspace/cryptanalysis/data/french_words
LE
DE
UN
ETRE
ET
A
IL
AVOIR
NE
JE
SON
QUE
SE
QUI
CE
DANS
I really don't understand why those exceptions are thrown, if somebody
could help it would be very nice. (It is for a crypto school project)
Thanks in advance. (Sorry for my english 'cause I'm french)
Here is a code snippet :
// Path to this class:
// /home/tom/workspace/cryptanalysis/utils/TextUtils.java
public abstract class TextUtils {
     private static String PATH;
     public static String[] KEYS;
     public static String[] WORDS;
     public static String[] PLAINTEXTS;
     public static float[] FREQUENCES;
      * Init KEYS, WORDS, PLAINTEXTS, FREQUENCES, and PATH,
      * with the files in the data folder.
     static {
          String line;
          PATH = TextUtils.class.getResource("../data/").toString();
          System.out.println(PATH);
          // When PATH is printed, it looks like this /home/tom/workspace/cryptanalysis/data/
          KEYS = FileUtils.readFileContent(PATH + "keys"); // Here is the first exception
          WORDS = FileUtils.readFileContent(PATH + "french_words");// Here is the second
          PLAINTEXTS = FileUtils.readFileContent(PATH + "french_texts");// Here is the third
          FREQUENCES = new float['['];
          try {
               BufferedReader reader = new BufferedReader(new FileReader(PATH + "french_frequences"));// And the fourth
               while(null != (line = reader.readLine()))
                    FREQUENCES[line.charAt(0)] += Float.parseFloat(line.substring(1));
          } catch (Exception e) {e.printStackTrace();}
// Path to this class:
// /home/tom/workspace/cryptanalysis/utils/FileUtils.java
public abstract class FileUtils {
      * Read the content of the file denoted by the given path and
      * return an array of Strings containing each line.
      * @param path
      * @return an array containing all the lines from the file
     public static String[] readFileContent(String path) {
          try {
               String line;
               Vector container = new Vector(100, 100);
               System.out.println(path);
               BufferedReader reader = new BufferedReader(new FileReader(path));
               while(null != (line = reader.readLine()))
                    container.add(line);
               return (String[])container.toArray(new String[container.size()]);
          }catch(Exception e) {e.printStackTrace();return null;}
     ....

vous �tes le type bienvenu
(thats bablefish for "you're welcome dude")Wow! That means "vous �tes bienvenu" means "You are welcome here" (i.e., "welcome at the forum", or whatever), not the proper answer to "Thank you".
The shortest form of "You're welcome" in the sense you intended it is "De rien". [literally, "of nothing"--so it would be something like if you said in English, "It was nothing."]

Any one has sample code of Multi-Thread Embbeded SQL in C ?

We want to write multh-thread code using Embbeded SQL in C.
The Open Client version is 15.7 SP100.
The Sybase Document : "Embedded SQL/C Programmers Guide (Open Client) " said it supports Multiple SQLCAs,
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Any one has sample code of Multi-Thread Embbeded SQL in C ?
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Hi,
I am asking around and will see if anyone has anything. Please note this though:
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Am adding up..
You can set the material status by using this path
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Cancel anonymous SwingWorker thread?

Hello,
A beginner question.
I have a button (A) calling a method, lets call it private void B().
Inside the method B() I have this:
SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() { do some stuff }
Anyway when I click the A button it calls the method b() and it works fine, the worker thread goes off and does what it needs to do.
If I want to implement a Cancel button to cancel the SwingWorker thread started by private void B(), how should I do it?
Thanks :)

Using SwingWorker is rather neat, and surprisingly studious for a beginner. Make sure that you do non-Swing related work in doInBackground() and Swing-related stuff in done(), that mostly what SwingWorker is for.Yes, that is the way I'm using it together with setProgress to update a progress bar.Great. I hadn't even ever noticed the existence of this method! I learn someting new everyday.
So, you're well ahead of me in terms of using the SwingWorker API! ;)
Your problem is definitely with the Java lanuage, not the SwingWorker.
Instead of using a local variable, make worker an attribute (of the class in which method b() is defined). Then in the action listener for the "Cancel" button, you can invoke the worker's cancel(boolean) method.
I'm not quite sure what you mean exactly when you say an attribute. The method b() is defined within the class that displays the Swing GUI:
public class ResyncWindow extends javax.swing.JFrame { } Do you want me to put the worker outside any methods?Yes, like this:
public class ResyncWindow extends javax.swing.JFrame {
    SwingWorker<Void, Void> worker;
    public ResyncWindow() {
        ... // create launchButton, and wire its actionListener to trigger b()
        ... // create cancelButton, and wire its actionListener to trigger cancel()
    private void b() {
        worker = new SwingWorker<Void,Void>() {
            public void doInBackground() {
                while (!isCancelled() { ..do stuff and set progress... }
        worker.execute();
        cancelButton.setEnabled(true);
        launchButton.setEnabled(false);
    private void cancel() {
         if (!worker.cancel()) {
             ... // display error
         cancelButton.setEnabled(false);
         launchButton.setEnabled(true);
}

Block T-code

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How block T-Code authorization.
Advance thanks
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Jack

Dear,
Which T .Code you wnat to block?
You want to block the user authorisation for T.Code then you can do through PFCG T-code. In PFCG authorization tab we neeed to maintain .
SU21 - Authorization object.
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What is the output of this block of codes of C? what about short-circuit true of C
when the user enter 5? i dont have C o r C++ so can anyone help me out, thanks.
int fun (int *x ) { return (*x)++; }
int main() {
int a;
a = 0;
printf("%d\n",a); /* prints the integer a, with newline to the screen */
scanf("%d",&a); /* scans an integer from the user into a */
if ( (a>0) && fun(&a) ) printf("%d",a); /* prints the integer a conditionally */
printf("%d\n",a);

What is the output of this block of codes of C? what
about short-circuit true of C
when the user enter 5? i dont have C o r C++ so can
anyone help me out, thanks.
int fun (int *x ) { return (*x)++; }
int main() {
int a;
a = 0;
printf("%d\n",a); /* prints the integer a, with
h newline to the screen */
scanf("%d",&a); /* scans an integer from the user
r into a */
if ( (a>0) && fun(&a) ) printf("%d",a); /* prints
s the integer a conditionally */
printf("%d\n",a);
}why would 5 cause a short-circuit?

How to write uninterruptable blocks of code in the RUN method of a THREAD?

Hello people,
It is better I explain my problem with example code
public class MyThreadClass implements Runnable
//some definitions
public void run()
//some codes
/*HERE I WANT TO WRITE A CODE WHICH WILL BE RUN AS ORDINARILY
FROM BEGINING TO THE END WITOUT ANY INTERRUPT*/
//some codes
Please help, if you can.
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Syncronized block of code

Hello there ...
Regarding of this topic. I've read that syncronized blocks helps to improve methods perfomance, but what I didn't understand was what do you pass to the sincronized line:
public void method(){
System.out.println("Not syncronized..");
syncronized(this)//what is this?
System.out.println("this is sincronized");
}It supossed to pass a reference of the object?
thanks in advance... any comment it's well recieved.
vanhalt

vanhalt wrote:
Hello there.
Thanks for replies. Your link was very useful... But now I didn't understand this piece of code:
public void method(){
syncronized(objReferenceA){
//use non-shared resources
syncronized(objReferenceB){
}regarding this piece of code it's supposed that I'm obtaining the locks for the objA and objB ? ... Yes. Note that this particular code is only taking one lock at a time. It gets lock A, then releases it, then does some work, then gets lock B then releases it.
and what happens with the lines of code that are not sincronized ? I mean other threads can access it ?..When a thread comes to one of those blocks, it will have to stop and wait if some other thread already has the lock that it's trying to obtain. If the two threads are obtaining two different locks (for example if their objReferenceA variables point to different objects) then both can execute concurrently.

How can we pass argument to static block of code????

hi ,
My question is we can use static initialization block for having functionality like constructors for initializing static variable ,but we cannot pass arguments to static initialization block then how can I create functionality like parametrized constructors.Whats the alternative shall I use a static method to perform this functionality,since all methods in given class are static and
there is no need of creating instance of class.

jduprez wrote:
Hello Jussi,Salut Jérôme
That's probably a more maintenable design.
However what do you base your remark on - I'm struck by the word obviously?
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In the OP's case, the "state" on which those methods operate is apparently fixed, presumably at the beginning of the program, so what's wrong with all this staticness?
I can list:
- threading issues (a non-issue after some initialization phase), that you wouldn't have with immutable instances
- harder unit-testing (that's not an OO design problem, more a methodology problem)
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Now we just need to have the OP explain his situation a bit better.

I want to know why it's happening me this error: Object synchronization method was called from an unsynchronized block of code.

I'm developing a Smart Array (it's a request I cannot use a List of int that I know it's easier because I made both codes). I have done this class and below is the example of how I use it. The error is often in this line (153 from class):
// Ensure that the lock is released.
Monitor.Exit(array);
If I use a List nothing wrong happens just when I translate to an array. Thanks for your help.
SmartArray3.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
namespace SmartArray
class SmartArray3
private int[] array;
private int size = 0;
private int count = 0;
public SmartArray3()
Resize(1);
public SmartArray3(int size)
this.size = size;
array = new int[this.size];
public bool Resize(int size)
try
if (array == null)
array = new int[size];
else
Array.Resize(ref array, size);
this.size++;
return true;
catch
return false;
private void add(int value)
try
if (array == null)
this.size = 1;
Resize(this.size);
array[0] = value;
this.count++;
else
if (this.count == (this.size - 1))
this.size *= 2;
this.Resize(this.size);
if ((this.count - 1) < 0)
array[0] = value;
else
array[this.count - 1] = value;
this.count++;
catch (Exception ex)
Console.Write(ex.ToString());
throw new System.IndexOutOfRangeException("Index out of Range.");
// Lock the array and add an element.
public void Add(int value)
// Request the lock, and block until it is obtained.
Monitor.Enter(array);
try
if (array == null)
this.size = 1;
Resize(this.size);
array[0] = value;
this.count++;
else
if (this.count == (this.size - 1))
this.size *= 2;
this.Resize(this.size);
if ((this.count - 1) < 0)
array[0] = value;
else
array[this.count - 1] = value;
this.count++;
finally
// Ensure that the lock is released.
Monitor.Exit(array);
// Try to add an element to the List: Add the element to the List
// only if the lock is immediately available.
public bool TryAdd(int value)
// Request the lock.
if (Monitor.TryEnter(array))
try
if (array == null)
this.size = 1;
Resize(this.size);
array[0] = value;
this.count++;
else
if (this.count == (this.size - 1))
this.size *= 2;
this.Resize(this.size);
if ((this.count - 1) < 0)
array[0] = value;
else
array[this.count - 1] = value;
this.count++;
finally
// Ensure that the lock is released.
Monitor.Exit(array);
return true;
else
return false;
public int Get(int index)
try
return array[index];
catch (IndexOutOfRangeException ex)
throw new System.IndexOutOfRangeException("Index out of range");
Code for called the Class:
private static int threadsRunning = 0;
private SmartArray3 sa = new SmartArray3();
private List<double> times;
private static string[] titles ={
"Add ", "Add failed ", "TryAdd succeeded ", "TryAdd failed "};
private static int[][] results = new int[3][];
//Event to Create Threads
private void newTest()
for (int i = 0; i < 3; i++)
Thread t = new Thread(ThreadProc);
t.Start(i);
Interlocked.Increment(ref threadsRunning);
private void ThreadProc(object state)
times = new List<double>();
DateTime finish = DateTime.Now.AddSeconds(10);
Random rand = new Random();
int[] result = { 0, 0, 0, 0};
int threadNum = (int)state;
while (DateTime.Now < finish)
Stopwatch sw = Stopwatch.StartNew();
int what = rand.Next(250);
int how = rand.Next(25);
if (how < 16)
try
sa.Add(what);
result[(int)ThreadResultIndex.AddCt] += 1;
times.Add(sw.Elapsed.TotalMilliseconds);
catch
result[(int)ThreadResultIndex.AddFailCt] += 1;
else
if (sa.TryAdd(what))
result[(int)ThreadResultIndex.TryAddSucceedCt] += 1;
else
result[(int)ThreadResultIndex.TryAddFailCt] += 1;
sw.Stop();
results[threadNum] = result;
if (0 == Interlocked.Decrement(ref threadsRunning))
StringBuilder sb = new StringBuilder(
" Thread 1 Thread 2 Thread 3 Total\n");
for (int row = 0; row < 4; row++)
int total = 0;
sb.Append(titles[row]);
for (int col = 0; col < 3; col++)
sb.Append(String.Format("{0,4} ", results[col][row]));
total += results[col][row];
sb.AppendLine(String.Format("{0,4} ", total));
Console.WriteLine(sb.ToString());
private enum ThreadResultIndex
AddCt,
AddFailCt,
TryAddSucceedCt,
TryAddFailCt
Federico Navarrete

The array that you're calling Monitor.Enter under is not always the same array that you call Monitor.Exit on. When you resize an array using Array.Resize, you pass the variable in as a reference parameter (ref). The method then creates a
new array object and assigns it to the array variable. Then, when you leave the synchronization block after resizing the array, your Monitor.Exit uses the new array rather than the one it originally entered
and... boom.
Instead of locking on the array itself, create a new private readonly field of type Object called "lock" within the SmartArray class and use that to lock on. It doesn't
need to be readonly, but the keyword will prevent you from accidentally introducing this issue again.

Close a blocking wait thrad by another thread

Hi all
I have a lookup method which makes a blocking wait and I want to close this lookup if the content not available for 10 seconds.
What I have done is put this lookup in a thread(LookupThread) and used separate thread(TimeCheckThread) for calculate the elapsed time.
This is my idea
public class LookupThread extends Thread
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    boolean closed = false;
    public TimeCheckThread getTimeChecker()
        return new TimeCheckThread();
    public void run()
        lookMethod(); // this is the blocking wait
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        long startTime = cal.getTimeInMillis();
        public void run()
            // strted looking for elapsed time
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        v.getTimeChecker().start();
        v.start();
}The problem is closing of thread is deprecated.
LookupThread.super.stop();So any idea to handle those blocking wait situations and assign a return time other than this approach?

WirajR wrote:
Also TimeCheckThread eats of CPU time for 10 seconds use a java.util.Timer instead
>Also TimeCheckThread eats of CPU time for 10 seconds use a java.util.Timer instead
Hi
I think this is the most suit to my requirement. Totally different way, but acceptable.
To EJP
Ur solution seems great to replace following code segment
public class TimeCheckThread extends Thread
        long startTime = cal.getTimeInMillis();
        public void run()
            // strted looking for elapsed time
            while(true)
                cal = Calendar.getInstance();
                if(cal.getTimeInMillis()-startTime > 10000 & !closed)
                    // if 10 seconds elapsed close the thread which makes the blocking wait
                    LookupThread.super.stop();
                    closed = true;
                    // to exit from time check thread
                    break;
    }like following
public class TimeCheckThread extends Thread
       public void run()
                    TimeCheckThread.sleep(10000);
                    LookupThread.super.stop();
}To Peter__Lawrey
Why don't you make the blocking lookup block for only 10 seconds?Any idea to implement such blocking lookup block?
My blocking operation is a looking for RTP video stream. It waits until server sends the video

Atomic block of code in SwingWorker thread?

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