Extending a class that implements java.io.Serializable interface

[Siphiwe Madi]

Hi All,

- Can anyone please let me know in simple terms, the meaning of a Serializable class and what does it imply for that class (which implements java.io.Serializable)?

- And when extending a class that implements Serializable - is it necessary to also state on the class-definition of the extending class that it implements Serializable?

e.g
1. class Parent extends java.lang.Object implements Serializable

2. class Child extends Parent

is line 2 enough

or should it read:
3. class Child extends Parent implements Serializable.

Thanks
Siphiwe M
SCJP 1.5 (aspirant)

[Yogvinder Singh Ghotra]

Serializable is a marker interface.

It implies that the class can be serialized and it's state can be stored on to the disk in a file.

when we extend a class that implements serializable we need not specify it again. this behavior is as per standard behavior of java.

Correct me if i am wrong.

[Lucky J Verma]

Serializable Class means
its objects can be serialized/persisted/saved.
As object is defined by its state which is turn is defined by its instance variables Value .
So Object and its State is saved on disk like any other file.
and later can be retireved.
eg
Before saving, Box class had an object b1( variables values ht=10 wt=70)
So with Serializable interface ,we can saved this object b1 ,with vales,later retrive same values.

2. No when super class implementing Serilizable,Chld class automatically implements Serializable.so need not explicit 'implements'

[Burkhard Hassel]

Howdy,

Welcome to the Ranch, Siphiwe!





this:

class Madi implements java.io.Serializable{
}
 
class Siphiwe extends Madi{
}
 
class Main {
public static void main(String[] args){
Siphiwe siphiwe = new Siphiwe();
System.out.println("siphiwe instance of Serializable ?");
if(siphiwe instanceof java.io.Serializable)
System.out.println("yes");
else 
System.out.println("no");
}
}

prints:
siphiwe instance of Serializable ?
yes


Some developers also would include the "implements Serializable" to the extending class, but only for clarity of the code.
But it's true, all extending classes implement all interfaces of the superclass automatically.

The javadoc tool also would include the fact that Siphiwe implements Serializable into the generated documentation.

Yours,
Bu.

[Siphiwe Madi]

Hi,

Thanks for the clarity. Now I understand.

Regards,
Siphiwe M