Creates a thread pool that can schedule commands to run after a given delay, or to execute periodically.

Parameters:

corePoolSize		the number of threads to keep in the pool, even if they are idle
threadFactory		the factory to use when the executor creates a new thread

Returns:  a newly created scheduled thread pool

Exceptions:

IllegalArgumentException		if corePoolSize < 0
NullPointerException		if threadFactory is null