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vivek shankare gowda
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Hi all..
I have a requirement..there are 4 people and each person hold a color balloon.. I need to ask them question at once.. But I need to print their answer only after 4 persons replied..

I created 4 threads to read answers..using thread names.. How I can store those answers and print after all threads excecutes..
 
Piet Souris
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hi Vivek,

well, if your program runs on the EDT, then I suggest you use 4 Swingworkers, and retrieve the answers in the 'done()' method.
This 'done()' method runs on the EDT as well, so you would not get any synchronisation problem here.

If you are not running from the EDT, then one possibility is: create, say, an ArrayLIst<String> (an Array would do fine as well),
start four threads, each writing to the arraylist once it has an answer. But for this writing, synchronize on this arraylist.
Then, for your main thread, join the four threads. You know then when there are four answers.

And then you could use executors, but that would be a bit overkill in this case.

Greetz,
Piet
 
vivek shankare gowda
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Hi Piet Souris,

Thanks for your reply. I used synchronized arraylist and stored values in the list. But I do not know how to use executors to print the answers once all threads are executed. Can you help me how I can iterate the list to print the answers
 
Piet Souris
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Well,

suppose your threads are: t1, t2, t3, t4, and that you've just started all of them.

Then you could do something like:

This is a very basic scheme, and forget that I mentioned the term 'executor'.
If you want to know more about threads, and there is plenty more to know,
have a look at the Concurrency tutorial from Oracle:
http://docs.oracle.com/javase/tutorial/essential/concurrency/index.html

Last remark: don't use this scheme if you are running your main thread in the
EDT (i.e. if you use some GUI program with windows and buttons and JPanels and so on
that runs from the so called 'Event Dispatch Thread'), or you will encounter a freezing GUI,
if t1, t2, t3 and t4 take more than a fraction of a second to finish.

Greetz,
Piet
 
Bin Smith
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Eclipse IDE Java
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It may look like this demo:
 
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