public void shutdown(){
  if (parallelExecutor != null && !parallelExecutor.isShutdown())   ExecutorUtil.shutdownAndAwaitTermination(parallelExecutor);
}

public void shutdown ( ) { if ( parallelExecutor != null && ! parallelExecutor . isShutdown ( ) ) ExecutorUtil . shutdownAndAwaitTermination ( parallelExecutor ) ; }
method to ensure shutting down of the threadpool executor .
