Problem with Classes and Interfaces

[jishnu dasgupta]

I have come across a problem while going though K&B book on EJB 2.0...It actually requires some knowledge of java to figure out..
I am not quoting the actual problem, although it is something like this.....I have the following classes and interfaces....

class A
{
    public void myMethod()
    {
    }
}

interface B extends C
{
     public void myMethod();
}
interface C
{
    //has some methods
}

The trick is to ensure that both A and B need to have the same method signatures, but i am not allowed to make A implements B
I though that may be I could try out with something like this as

class D extends A implements B
{
} 

as this would check whether the method declared by B is implemented by A, but then again, B extends C, and i need to provide implementation for C, whose methods i am not aware Of.

Can you please suggest some way in which i can ensure That the method definition in A matches the method declartion in B??

P.S: just to give a background, this concerns itself with component interfaces and bean classes

[Wouter Oet]

Why isn't A allowed to implement B?

[jishnu dasgupta]

Wouter,

From my example point of view if A implemnets B, then A has to implement C as well, whos methods A is neither aware of, nor required to implement.

From the actual problem point of view, A is a bean class and B is a component interface and C is an EJBObject. The spec requires that A should not implement B. If we do know the methods in EJBObject and we do provide the their implementation in A, then it would mean that the client would be able to directly communicate with the bean class, through the EJBObject methhods that the bean class defines, which again is a violation of Bean architecture.

[jishnu dasgupta]

Is there a solution???

[Matthew Brown]

Sounds like you possibly want something like this:

interface C {
   ...
}

// this interface contains the additional methods you want in B and A
interface D {
   public void myMethod();
}

interface B extends C, D {}

class A implements D {
    public void myMethod() {  
        ...
    }  
}

[Mak Smash]

Hi,

If you implement an interface B and that interface extends to another interface C that time you must have to implement method of both the interface otherwise compiler wont allow...

If you dont know what methods interface C has... you can find using javap -p InterfaceName... This will show you all the methods inside that interface...

[jishnu dasgupta]

Matthew Brown wrote:Sounds like you possibly want something like this:

interface C {
   ...
}

// this interface contains the additional methods you want in B and A
interface D {
   public void myMethod();
}

interface B extends C, D {}

class A implements D {
    public void myMethod() {  
        ...
    }  
}

Agreed!!!...Thanks a lot. Really was very simple

[jishnu dasgupta]

Mak Smash wrote:Hi,

If you implement an interface B and that interface extends to another interface C that time you must have to implement method of both the interface otherwise compiler wont allow...

If you dont know what methods interface C has... you can find using javap -p InterfaceName... This will show you all the methods inside that interface...

Yes I can, but that option is not viable due to some design issues.