— Scott McNealy, Sun Microsystems Chairman, President and ceo

What happens if two objects in 
the object graph are the same object? 
Like, if you have two different Cat 
objects in the Kennel, but both Cats 
have a reference to the same Owner 
object. Does the Owner get saved 
twice? I’m hoping not.
A: 
Excellent question! Serialization 
is smart enough to know when two 
objects in the graph are the same. In 
that case, only one of the objects is 
saved, and during deserialization, any 
references to that single object are 
restored. 
serialized 
objects
there are no
Dumb Questions

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serialization 
and
file I/O
you are here
4
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Deserialization: restoring an object
The whole point of serializing an object is so that you can 
restore it back to its original state at some later date, in a 
different ‘run’ of the JVM (which might not even be the same 
JVM that was running at the time the object was serialized). 
Deserialization is a lot like serialization in reverse.
FileInputStream fileStream = new FileInputStream(“MyGame.ser”);
Make a FileInputStream object. The FileInputStream 
knows how to connect to an existing file.
1
Make a FileInputStream
Object one = os.readObject();
Object two = os.readObject();
Object three = os.readObject();
3
read the objects
os.close();
5
Close the ObjectInputStream
Closing the stream at the top closes the ones 
underneath, so the FileInputStream (and the 
file) will close automatically.
If the file “MyGame.ser” doesn’t 
exist, you’ll get an exception.
ObjectInputStream os = new ObjectInputStream(fileStream);