Concurrency Questions

["Dale Bronk - Windscape" <dbronk@windscape.com>]

Hello,

 

I have two questions.  Please assume multiprocessor machines with each thread running on separate cpu's.  Also, if you can point me to any reference that backs your opinion/fact would be great.  Am I safe on both of the following?

 

1.  Lets say I have the following code:

 

public class MyTest extends Thread

{

    static int i = 0;

 

    // Please not NO sync's

    run()

    {

        i++;

    }

}

 

Now let's say that I spawn 2 of these and they are on different cpu's and they both execute i++ at the same time.  Is there EVER a chance that the result of i can EVER be 1 or will it always be 2.

 

 

2.  Now here is another code snippet:

 

static ArrayList myStaticList = null;

public ArrayList getList(boolean shouldRefresh)

{

    if (shouldRefresh)

    {

        // Not only sync on refreshing, not getting

        synchronized (someLockObject)

        {

            ArrayList newList = new ArrayList();

            //  Code here to get new list from database and fill newList

            myStaticList = newList;

        }

    }

    return myStaticList;

}

 

My question is that let's say that one thread (different cpu) is executing return myStaticList at the same time as another thread is executing myStaticList = newList.  Is it possible that the return myStaticList will EVER return a half/limbo state object or worse yet a Dr. Watson or something?

 

Help is wanted and appreciated.

 

Thanks,

Dale