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SwingWorker in try/catch

When I do this:

try {
outputStream = new PrintWriter(new FileWriter("myfile.txt");
outputStream.println("execute"); 
new ProgressTask().execute();
outputStream.close();
} 
catch (IOException e) {
e.printStackTrace();
}

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ProgressTask.doInBackground() is not called. But when I move the call to execute() outside the try/catch:

try {
outputStream = new PrintWriter(new FileWriter("myfile.txt");
outputStream.println("execute"); 
} 
catch (IOException e) {
e.printStackTrace();
}
new ProgressTask().execute();
outputStream.close();

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it is called. Why?
No exception is being thrown, so it is making it to new ProgressTask().execute(); in both cases.

private class ProgressTask extends SwingWorker<Void, Void> {
		
public Void doInBackground() {
	try {
		System.out.println("Sleeping for two secs...");
		Thread.sleep(2000);
	} catch (InterruptedException e) {
		/* ignore */
	}
	return null;
}

public void done() {
	jProgressBar.setIndeterminate(false);
}
}

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0
allelopath
Asked:
allelopath
4 Solutions
 
CEHJCommented:
Can you give more complete code context please? Preferably something that's runnable that demos the problem
0
 
for_yanCommented:
How can you have outputStream.close() not within the try/catch loop in the second case - wouldn't compiler caomplain?
0
 
dpearsonCommented:
This can't be the actual code you're running since this line:

outputStream = new PrintWriter(new FileWriter("myfile.txt");

clearly won't compile (it's in both examples and it missing a closing brace).

The only difference in the execution path for your two examples depends on whether there's an exception thrown or not.  So:
1) Either it is throwing an exception and you're just not seeing the output from the exception for some reason
or
2) This isn't the key part of the code and something else is causing the problem.

Doug
0
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objectsCommented:
you don't need a SwingWorker to achieve that
thats what a Swing timer is for, far simpler
0
 
objectsCommented:
All you need is this:

               Timer timer = new Timer(2000, new ActionListener() {
                  public void actionPerformed(ActionEvent e) {
                        setProgressIndeterminate(true);
               });
               timer.setRepeats(false);
               timer.start();

And having it inside the try/catch will mean it will not get called if an exception is thrown opening/writing the file
0
 
allelopathAuthor Commented:
Thanks for the responses. Allow me to refine the question to this:
Is there something intrinsically incorrect with calling ProgressTask().execute(); from within a try/catch?
0
 
dpearsonCommented:

Is there something intrinsically incorrect with calling ProgressTask().execute(); from within a try/catch?]

No - it's fine to call any code inside a try {} catch {} block.

Indeed most production applications run all code inside a top level try...catch block, so an exception which propagates to the top level doesn't shutdown the application.

Doug
0

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