Getting Data from Tasks - The Callable and Future Interfaces

In Chapter 3, Managing Lots of Threads - Executors, and Chapter 4, Getting the Most from Executors, we introduced the Executor framework to improve the performance of concurrent applications and showed you how to implement advanced characteristics to adapt this framework to your needs. In these chapters, all the tasks executed by the executor were based on the Runnable interface and its run() method that doesn't return a value. However, the Executor framework allows us to execute other kinds of tasks that return a result based on the Callable and Future interfaces. Callable is a functional interface which defines the method call(). The method call() may throw a checked Exception which is different to the Runnable interface. The result of a Callable interface process is wrapped by the Future interface. The Future...