Re: Synchronization with threads

Daniel Pitts <>
Fri, 08 Feb 2008 07:52:30 -0800
Kevin McMurtrie wrote:

In article <47ac73d4$0$14886$>,
 Daniel Pitts <> wrote: wrote:


I have a class which is not a thread which executes the following
public void myFunc() {
MyMainThread thread = new MyMainThread();

A thread creates many subthreads which role is to fill in the
ArrayList (defined for thread). Next, I would like to pass this
arrayList to myFunc in the moment when all subthreads have finished
its job (so that I am sure that arraylist is complete) and immediately
start exec method.

I have two problems:
- how to pass this arrayList from thread (can I simply use method from
thread to return it? will the thread be still active?)
- how can I suspend an execution of myFunc() till the mainThread
finish creating arrayList?

Would be very grateful for effective solutions of these problems.

Regards, Mark

this sounds like a bad idea, unless you make sure your using proper

I suggest looking into the standard ExecutorService and
CompletionService classes.

There's nothing wrong with that. The ArrayList can be accessed if it's
final and the Thread/Runnable is an anonymous inner class. It can also
be accessed if the array is a field of the class. It can be passed in
the constructor for a Thread subclass. Many options.

I didn't say the array wasn't accessible.

Each thread will have to synchronize on a common object, probably the
ArrayList itself, while working on it. Call join() on each Thread to
block until it completes.

That would be the way to do it with his current approach, but I was
suggesting he look into a much cleaner, more efficient, and
easier-to-get-correct solution.

Daniel Pitts' Tech Blog: <>

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