=== shutdown(): lets running AND already-queued tasks finish ===
task-0: started
task-1: started
main: called shutdown() - isShutdown=true, isTerminated=false
task-0: finished normally
task-2: started
task-1: finished normally
task-3: started
task-3: finished normally
task-4: started
task-2: finished normally
task-5: started
task-4: finished normally
task-5: finished normally
main: awaitTermination returned true - all 6 tasks ran to completion, none were skipped

=== shutdownNow(): interrupts running tasks, abandons queued ones ===
task-0: started
task-1: started
main: called shutdownNow() - 4 queued tasks abandoned, never started
task-1: interrupted, exiting early
task-0: interrupted, exiting early
main: awaitTermination returned true - the 2 running tasks were interrupted mid-sleep, not allowed to finish
done