code: protected ScheduledExecutorService createExecutor(int poolSize, ThreadFactory threadFactory,
              RejectedExecutionHandler rejectedExecutionHandler) {
          return new ScheduledThreadPoolExecutor(poolSize, threadFactory, rejectedExecutionHandler);
      }
docs: Create a new {@link ScheduledExecutorService} instance.
  <p>
  The default implementation creates a {@link ScheduledThreadPoolExecutor}.
  Can be overridden in subclasses to provide custom
  
  @param poolSize the specified pool size
  @param threadFactory the ThreadFactory to use
  @param rejectedExecutionHandler the RejectedExecutionHandler to use
  @return a new ScheduledExecutorService instance
  {@link ScheduledExecutorService} instances.
  @see #afterPropertiesSet()
  @see java.util.concurrent.ScheduledThreadPoolExecutor