Scheduled thread pool is an extension of the basic thread pool of the Executor framework that allows you to schedule the execution of tasks to be executed after a period of time. It's implemented by the ScheduledThreadPoolExecutor class, and it permits the execution of the following two kinds of tasks:

• Delayed tasks: These kinds of tasks are executed only once after a period of time
• Periodic tasks: These kinds of tasks are executed after a delay and then periodically, every so often

Delayed tasks can execute both Callable and Runnable objects, but periodic tasks can only execute Runnable objects. All the tasks executed by a scheduled pool are an implementation of the RunnableScheduledFuture interface. In this recipe, you will learn how to implement your own implementation of the RunnableScheduledFuture interface to execute both delayed and periodic tasks.