About Question enthuware.ocpjp.v11.2.3637 :

[gadsgadsx]

Won't the es.shutdown() force the last thread (5 thread) to finish?

[exclusivewild]

In Java, the behavior of es.shutdown() (where es is an instance of ExecutorService) does not forcefully terminate currently running tasks. Instead, it initiates an orderly shutdown of the ExecutorService in which previously submitted tasks are executed, but no new tasks will be accepted.