You may have noticed the class
in the previous diagram.
Streams of that class write objects to a
destination such as a disk file.
ObjectInputStream streams read objects from
So far in our programs objects have existed only in
main memory and lasted only as long the program that
created them was running.
When the program stopped running (or earlier),
they were garbage collected.
ObjectOutputStream an object can
be written to disk and will remain there even after
the program stops.
This is the topic of object serialization,
an advanced topic not yet covered in these notes.