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Null Interface

 
Prashanth Paul
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Hi All ,
I am curious know something about the Null interface . What are they ? Can Cloneable , Serializable be called as Null interfaces ? Please let me know.
Thanks.
 
Valentin Crettaz
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...
A null interface is an interface with no method declaration. I don't really like this term since "null" has a special meaning in Java. I would prefer calling such an interface an "empty interface" or better a "tag interface" but not a "null interface". Maybe someone else has an idea as to why such interfaces have been called "null interfaces".
I don't know who invented that but "null interface" does not exist in the official Java terminology.
[ December 10, 2002: Message edited by: Valentin Crettaz ]
 
Manish Hatwalne
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Aren't they called Marker Interfaces?
- Manish
 
Valentin Crettaz
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Marker and Tag are synonym in my opinion.
Wiki provides some good explanations:
Tag Interface
Marker Interface
 
Gustavo Adolpho Bonesso
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Would somebody give some examples of null interfaces ?
 
shweta mathur
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RandomAccess Interface implemented by Vector class & ArrayList is a Marker Interface
 
Ashik Uzzaman
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Marker interface, also known as Tag interface, are like directives to the compiler without any method declaration. It is implemented in a class so that other java codes and JVM can test an object of it with "instanceof interface". java.io.Serializable, java.lang.Cloneable, java.util.EventListener, java.util.RandomAccess are marker interfaces from J2SE API that I can recall quickly.

To support with an example from the J2SE API Documentation, you'll see that Serializable is a marker interface, in its comment its written that All subtypes of a serializable class are themselves serializable.

BTW shewta, ArrayList is a concrete final class, its not an interface rather an implementation of RandomAccess marker interface.

Regards,
 
Pradeep bhatt
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BTW shewta, ArrayList is a concrete final class, its not an interface rather an implementation of RandomAccess marker interface.


ArrayList is not a final class.
 
Tony Morris
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An interface containing no methods (a tag/marker interface) is poor form, however, the core API has done it, and many other, more disastrous, atrocities. You need not be so concerned with it.
 
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