— Scott McNealy, Sun Microsystems Chairman, President and ceo

part is, it happens automatically!
Dog
foof
Dog
barf
C
oll
a
r 
ob
jec
t
S
t
rin
g
o
bjec
t 
Do
g[
] 
a
rr
a
y
o
b
j
e
c
t
int
String
name
Collar
col
D
o
g 
o
b
j
ect
size
“Fido”
C
oll
a
r 
ob
jec
t
S
t
rin
g
o
bjec
t 
int
String
name
Collar
col
D
o
g 
o
b
j
ect
size
“Spike”
This Kennel object has a reference to a Dog [] array object. The 
Dog [] holds references to two Dog objects. Each Dog object holds 
a reference to a String and a Collar object. The String objects 
have a collection of characters and the Collar objects have an int.
When you save the Kennel, all of this is saved!
Ken
n
e
l
obj
e
c
t
Dog [ ]
dogs
Serialization saves the 
entire 
object graph
. 
All objects referenced 
by instance variables, 
starting with the 
object being serialized.
serialized 
objects
Everything has to 
be saved in order to 
restore the 
Kennel back 
to this state. 

---

serialization 
and
file I/O
you are here
4
437
If you want your class to be serializable, 
implement 
Serializable
The Serializable interface is known as a marker or tag interface, 
because the interface doesn’t have any methods to implement. Its 
sole purpose is to announce that the class implementing it is, well, 
serializable. In other words, objects of that type are saveable through 
the serialization mechanism. If any superclass of a class is serializable, 
the subclass is automatically serializable even if the subclass doesn’t 
explicitly declare implements Serializable. (This is how interfaces always 
work. If your superclass “IS-A” Serializable, you are too).