Executor Framework

The previous lesson covered thread pools and how reusing a fixed set of worker threads beats spawning a new Thread for every task. This lesson covers the API used to talk to a pool: the Executor interface, its richer cousin ExecutorService, the Executors factory class, and the lifecycle methods (shutdown, shutdownNow, awaitTermination) that decide when the program is allowed to exit. We'll build an order-confirmation pipeline for an online store, submit tasks to a pool, shut it down cleanly during a deployment, and look at what happens when the shutdown step is skipped.

The running example uses Runnable tasks so the API stays in focus.