Implementing an interface with generic type methods

Thread view:

Mize-ze - 13 Nov 2006 11:07 GMT

I want to create an interface with two methods

The classes that will implement this interface will sometimes need the
methods with different arguments and return types. how can this be
done? what is the simpliest solution? I realize that it can be two
different interfaces but that is really not good with my design.

An example of what I want will make it clearer:

public interface MyInterface
{
public ??? foo(??? arg)
public ??? bar(??? arg)
}

public classA implements MyInterface
{
public String foo(String arg);
public String bar(String arg);
}

public classB implements MyInterface
{
public int foo(Object arg);
public String bar(Object arg);
}

Thanks.

Reply to this Message

Eelco - 13 Nov 2006 11:42 GMT

You can do it like this:

> public interface MyInterface
> {
[quoted text clipped - 11 lines]
> public String bar(Object arg);
> }

This way you have a common interface with no abstract methods
specified.

Hope this helps.

Best regards,
Eelco

Reply to this Message

Mize-ze - 13 Nov 2006 12:03 GMT

Thanks Eelco,
I Guess that will work but what the point of doing it?

> You can do it like this:
>
[quoted text clipped - 21 lines]
> Best regards,
> Eelco

Reply to this Message

Mark Jeffcoat - 13 Nov 2006 15:08 GMT

> Thanks Eelco,
> I Guess that will work but what the point of doing it?

Please don't top post.

You have to tell us what the point of doing it is if
you want a useful answer.

Pending that, you may have set up a situation that Java's
type system doesn't handle particularly gracefully, and
you'll have to define the interface's methods to accept
and return Object. Most of the time I see that, though,
there's a better way--more idiomatic, at least.

Signature

Mark Jeffcoat
Austin, TX

Reply to this Message

Ingo R. Homann - 13 Nov 2006 12:22 GMT

Hi,

> An example of what I want will make it clearer:
>
[quoted text clipped - 15 lines]
> public String bar(Object arg);
> }

Whats wrong with:

public interface MyInterface<FooParam,FooReturn,BarParam,BarReturn> {
public FooReturn foo(FooParam arg);
public BarReturn bar(BarParam arg);
}

public classA implements MyInterface<String,String,String,String>
{
public String foo(String arg){...}
public String bar(String arg){...}
}

public classB implements MyInterface<Object,Integer,Object,String>
{
public Integer foo(Object arg){...}
public String bar(Object arg){...}
}

Ciao,
Ingo

Reply to this Message

Mize-ze - 16 Nov 2006 13:02 GMT

Ingo,
Excactly what I wanted

Thanks

> Hi,
>
[quoted text clipped - 39 lines]
> Ciao,
> Ingo

Reply to this Message

Implementing an interface with generic type methods

Free Magazines