title: SimpleAsyncTaskExecutor not releasing threads
body: <p>I am running several spring batch partitioning jobs from within the same JVM instance. Each is configured to use 3 threads but every time a new job starts I see in the logs that <code>SimpleAsyncTaskExecutor</code> keeps increasing its thread number.</p>
  
  <p>so first jobs shows:</p>
  
  <blockquote>
    <p>09:53:02.370 [SimpleAsyncTaskExecutor-1] INFO...
    <br>09:53:02.370 [SimpleAsyncTaskExecutor-2] INFO...</p>
  </blockquote>
  
  <p>and next jobs shows:</p>
  
  <blockquote>
    <p>09:53:02.370 [SimpleAsyncTaskExecutor-3] INFO...
    <br>09:53:02.370 [SimpleAsyncTaskExecutor-4] INFO...</p>
  </blockquote>
  
  <p>I would have expected each new job to use threads 1 and 2 and not create new ones...I am shutting down the job each time but can post code if needed.</p>