What is the best way to wait for the completion of all workers in a thread pool?

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Imagine I have following code:

final ExecutorService threadPool = Executors.newFixedThreadPool(
    NUMBER_OF_WORKERS);

for (int i=0; i < NUMBER_OF_WORKERS; i++)
{
  final Worker worker = new BirthWorker(...);
  threadPool.execute(worker);
}

Now I need a piece of code, which waits, until all workers have completed their work.

Options I'm aware of:

1. while (!threadPool.isTerminated()) {}


2. 
   

   Modify the code like that:

   
   

   final List futures = new ArrayList(NUMBER_OF_WORKERS); final ExecutorService threadPool = Executors.newFixedThreadPool(NUMBER_OF_WORKERS);

   
   

   for (int i=0; i < NUMBER_OF_WORKERS; i++) { final Worker worker = new Worker(...); futures.add(threadPool.submit(worker)); }

   
   

   for (final Future future : futures) { future.get(); }

   
   

   // When we arrive here, all workers are guaranteed to have completed their work.

   
   

What is the best practice to wait for the completion of all workers?

asked 13 secs ago

Dmitri Pisarenko

1,282

What is the best way to wait for the completion of all workers in a thread pool?