Question

Here is my code snippet.

ExecutorService executor = Executors.newFixedThreadPool(ThreadPoolSize);
while(conditionTrue)
{
ClassImplementingRunnable c = new ClassImplementingRunnable();
executor.submit(c);
}

Now after this is do

executor.shutdown();

What i want to achieve here is that i want to wait for all the threads in the threadpool to have finished the execution and then i want to shutdown the executor.

But i guess this is not what is happening here. The main thread seems to be executing shutdown and it just shuts down everything.

Before when my threadpool size was 2, i did the following and it seemed to work.

ClassImplementingRunnable c1 = new ClassImplementingRunnable();
executor.submit(c1);
ClassImplementingRunnable c2 = new ClassImplementingRunnable();
executor.submit(c2);
Future f1 = executor.submit(c1);
Future f2 = executor.submit(c2);
while(!f1.done || !f2.done)
{}
executor.submit();

How do i do this for a greater number of threads in the threadpool?
Thanks.

Answer 1

You generally use the following idiom:

executor.shutdown();
executor.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);

• shutdown just says that the executor won’t accept new jobs.
• awaitTermination waits until all the tasks that have already been submitted finish what they are doing (or until the timeout is reached – which won’t happen with Integer.MAX_VALUE – you might want to use a lower value).