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javainheritanceinterface
JohnH
JohnH

Reputation: 150

Java interface types basic question

I have a basic question with Java interfaces.

Say if I have a interface IA and interface IB extends IA

now, 

class CK implements IB,
class CL implements IB,
class CM implements IB,

... etc

void foo(IA iFace) {
// I know how to check if iFace is of type CK/CL/CM ...

// Is it possible to check if iFace is of type IB ?

}

Hope my question is clear.

Thanks for any replies.

Upvotes: 0

Views: 507

Answers (3)

Richard Tagger
Richard Tagger

Reputation: 55

Use instanceof as follows:

if(ObjectA instanceof ObjectB)
{
     //hooray, it is
}

Bear in mind that if B extends A, and you have K, L, M implementing B, they are an instance of B and A.

When you extend a class, you inherit from it and everything it has inherited from.

Upvotes: 0

Peter
Peter

Reputation: 1013

you can use the instanceof keyword

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1500515

You can check using instanceof:

if (iFace instanceof CK)

etc

... but it's generally a sign that your design has gone wrong, if you have to handle things differently. The idea of the interface should be that you can treat them all the same way, and let the implementations behave differently in an appropriate way.

It doesn't always work out that way, so sometimes instanceof is the best you can do, but that should be a rarity.

Upvotes: 9

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