Re: HashMap.keySet().iterator() and threads

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#7373

From: Torsten Welches
Date: Mon, 25 Jun 2001 09:55

25 lines
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"Petar Banicevic" <petar_b@usa.net> wrote:

>while (localStack.keySet().iterator().hasNext()) {
> String fileName=(String)localStack.keySet().iterator().next();
>}
>
>Now, what would happen if somebody else, out of this thread, 
>adds/removes a few lines in localStack while this loop is >running. LocalStack is HashMap.

a java.util.ConcurrentModificationException would be thrown.

BTW - you code does probably not what you expect it to do. 
In your while body you get a *new* iterator each time and call 
next on that. You would end up getting the first item all the 
time.

I guess that's what you want instead:

Iterator it = localStack.keySet().iterator();
while (it.hasNext()) {
  String fileName=(String)it.next();  
}

Torsten

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