The output order is due to the asynchronous nature of the tasks. The line “Patrick’s Komputer: hey hey” is printed immediately because it’s a synchronous operation. The other lines are printed later by an asynchronous task that was queued to run after the synchronous operations. This task prints “Patrick’s Komputer: howdy!”, waits for 2 seconds, and then prints “Patrick’s Komputer: done!”. So, the output order is not the same as the order in the code.
drop(spawner) in the code signals to the Executor that no more tasks will be added to the queue. When it is removed, the Executor might keep waiting for more tasks even after all tasks have been executed. This leads to the program not terminating.