About visibility of variables in concurrency

Hi,
I have a class that implements Runnable, and it has a constructor. As we know to ensure the change visibility of variables in different threads we need to use the "volatile" key word.
So if I do not use "volatile," and contruct the object in the main thread, and then access and modify them in the run() method, could there be any problem? (after construction the run() method is the only place these variables are accessed and modified)
Thanks!

808239 wrote:
Hi,
I have a class that implements Runnable, and it has a constructor. As we know to ensure the change visibility of variables in different threads we need to use the "volatile" key word.
Not true.
First, variables' visibility is unaffected by multithreading. Presumably you're talking about the variables' values.
Second, volatile is not the only way. Making sure all access to those variables occurs in synchronized blocks or methods also ensure that threads see each others' updates. Or you could use the classes in java.until.concurrent.atomic. Which one is appropriate depends on your particular needs, of course.
So if I do not use "volatile," and contruct the object in the main thread, and then access and modify them in the run() method, could there be any problem? (after construction the run() method is the only place these variables are accessed and modified)If there's a shared variable, and you don't mark it volatile or sync all access to it, then, yes, you don't know when or even if one thread will see another thread's write of that variable.
However, it sounds like you're saying only one thread is even using these variables. If so, this is not an issue. If you're worried about a child thread seeing the values that the parent set before start()ing the child, it's not a problem. Writes that occur before starting a thread have a "happens-before" relationship with all accesses in that new thread.
Edited by: jverd on Mar 9, 2011 2:36 AM

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angeshwar wrote:
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� {�

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Basically I want to know if declaring
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About visibility of variables in concurrency

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