Re: ArrayList - Reading and writing
Jimmie Tyrrell wrote:
Got a Java-y question:
I have a loop that executes periodically. The loop iterates over an
Array List, and processes each item.
Randomly, a UDP socket will receive some data, which is then appended
to the Array List.
The problem, naturally, is that my Iterator will throw an exception if
data is received while I'm Iterating over the ArrayList.
Catching the exception is okay - but it occurs while Iterating. I'd
prefer the Iteration process to go untouched, and instead maybe
receive the Exception while _writing_ the data. I could then cache
it, or simply ignore it, whatever.
Any suggestions on how to achieve this? Need to see some code to
understand the problem?
As some others have pointed out, you need to synchronize the access to
the list.
Now, if it turns out that your UDP handler blocks too long because of
the iteration, you might consider having all the UDP code put the
results into a BlockingQueue (LinkedBlockingQueue or ArrayBlockingQueue,
depending).
Then you can replace all access to the ArrayList with a getter, and the
getter could first drain the blocking queue into the array list before
returning it. That way, you don't need explicit synchronization between
the UDP handling code and the iterating code, the BlockingQueue does it
for you.
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