Touring Additional Utility APIs - Beginning Java 7 - page 544

Note The java.util.concurrent.ScheduledExecutorService inter-
face extends ExecutorService and describes an executor that lets you schedule
tasks to run once or to execute periodically after a given delay.

Although you could create your own Executor , ExecutorService , and
ScheduledExecutorService implementations (such as class DirectEx-
ecutor implements Executor { public void execute(Runnable
r) { r.run(); } } —runexecutordirectlyonthecallingthread),theconcurrency
utilities offer a simpler alternative: java.util.concurrent.Executors .

Tip If you intend to create your own ExecutorService implementations,

you will find it helpful to work with the

and

java.util.concurrent.AbstractExecutorService

java.util.concurrent.FutureTask classes.

The Executors utility class declares several class methods that return instances
ofvarious ExecutorService and ScheduledExecutorService implementa-
tions(andotherkindsofinstances).Thisclass's static methodsaccomplishthefol-
lowing tasks:
• Create and return an ExecutorService instance that is configured with
commonly used configuration settings.
• Create and return a ScheduledExecutorService instance that is con-
figured with commonly used configuration settings.
• Create and return a “wrapped” ExecutorService or ScheduledEx-
ecutorService instance that disables reconfiguration of the executor ser-
vice by making implementation-specific methods inaccessible.
• Createandreturna java.util.concurrent.ThreadFactory instance
for creating new threads.
• Create and return a Callable instance out of other closure-like forms so
thatitcanbeusedinexecutionmethodsrequiring Callable arguments(e.g.,
ExecutorService 's submit(Callable) method). (Check out Wikipe-
dia's “Closure (computer science)” entry [ http://en.wikipedia.org/
wiki/Closure_(computer_science) ] to learn about closures.)
For example, static ExecutorService newFixedThreadPool(int
nThreads) createsathreadpoolthatreusesafixednumberofthreadsoperatingoffa
sharedunboundedqueue.Atmost, nThreads threadsareactivelyprocessingtasks.If