Newbie - I don't understand interface Serializable

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zalek - 28 Jun 2008 17:23 GMT

The interface Serializable does not have any methods or variables.
If I create a subclass of an Object class - is this class
Serializable?
For example, let say I define:

public class A extends Object{
int a;
}

Now make the following definition:

public class A extends Object implements Serializable{
int a;
}

What makes the 2nd definition Serializable?

Thanks,

Zalek

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Lasse Reichstein Nielsen - 28 Jun 2008 17:32 GMT

> The interface Serializable does not have any methods or variables.

Correct. It's a "marker interface" which merely marks the class as being
intended for serialization. The serialization code checks for the marker,
and refuses to serialize something without it - not because it couldn't,
but just because it won't - serializing and derserializing something not
build for it could cause unexpected trouble.

Today it would probably have been implemented as an inherited
annotation.

> If I create a subclass of an Object class - is this class
> Serializable?

If it implements the Serializable interface.

> For example, let say I define:
>
> public class A extends Object{
> int a;
> }

Yes, that class isn't serializable. No need to write the "extends Object".
The class will automatically extend Object if no other superclass is
given.

> Now make the following definition:
>
[quoted text clipped - 3 lines]
>
> What makes the 2nd definition Serializable?

That it implements the interface! That means that the default
serialization code will accept to serialize and deserialize objects
of that class.

/L

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Lasse Reichstein Nielsen
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Mark Space - 28 Jun 2008 19:01 GMT

> The interface Serializable does not have any methods or variables.
> If I create a subclass of an Object class - is this class
> Serializable?

Lasse gave you some really good answers to your questions. Here's a
decent how-to on serialization from Sun. It explains further how
serialization actually works and gives some guidelines how to use it.

<http://java.sun.com/developer/technicalArticles/Programming/serialization/>

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Mike Schilling - 29 Jun 2008 04:16 GMT

>> The interface Serializable does not have any methods or variables.
>> If I create a subclass of an Object class - is this class
[quoted text clipped - 6 lines]
>
> <http://java.sun.com/developer/technicalArticles/Programming/serialization/>

And her is everything you'd ever want to know about serialization:
http://java.sun.com/j2se/1.3/docs/guide/serialization/spec/serialTOC.doc.html

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Arne Vajhøj - 29 Jun 2008 04:38 GMT

>>> The interface Serializable does not have any methods or variables.
>>> If I create a subclass of an Object class - is this class
[quoted text clipped - 9 lines]
> And her is everything you'd ever want to know about serialization:
> http://java.sun.com/j2se/1.3/docs/guide/serialization/spec/serialTOC.doc.html

I don't think it has changed, but:

http://java.sun.com/javase/6/docs/platform/serialization/spec/serialTOC.html

Arne

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Roedy Green - 29 Jun 2008 02:29 GMT

On Sat, 28 Jun 2008 09:23:07 -0700 (PDT), zalek
<zalekbloom@hotmail.com> wrote, quoted or indirectly quoted someone
who said :

>The interface Serializable does not have any methods or variables.
>If I create a subclass of an Object class - is this class
>Serializable?
>For example, let say I define:

it is just marker to indicate you have thought through the class to do
the transients etc. needed to make it serialisable.

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Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com

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Newbie - I don't understand interface Serializable

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