Practice with thread pools

They have the difficulties backwards on this set of tasks. The first two are easy (they literally tell you every step of the process). The last one is hard. I've been googling for a bit and I still have no idea how to even approach this. I thought maybe enclosing the method call in a try/catch with InterruptedException but it just says that it never throws that type of exception. I tried putting the Runnable objects in an arraylist so that i could iterate through them after the shutdownnow method to find out which ones were interrupted, but that's not working either.

1.创建ExecutorService实例，并用submit方法添加任务。或者创建ThreadPoolExecutor实例，用prestartAllCoreThreads启动核心线程。 2.shutdown()会关闭executor，但是已经添加的任务会被完成。shutdownNow()会立即关闭executor并且返回已经添加但是没有完成的任务。

shutdownNow() returns list...

Task3: The example output conflicts with validation. Do not remove square brackets when printing Runnable

for "Introducing ThreadPoolExecutor" check link: https://stackoverflow.com/questions/17659510/core-pool-size-vs-maximum-pool-size-in-threadpoolexecutor