Re: Interface Method with Interface Parameter

From:
Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 01 Nov 2007 18:19:02 -0700
Message-ID:
<3fKdnQwr04gQ5rfanZ2dnUVZ_uevnZ2d@wavecable.com>
Owen Jacobson wrote:

On Nov 1, 2:24 pm, Edward.Sht...@gmail.com wrote:

I must be breaking some rule of Object-Oriented Programming, but I
can't figure out how else to do it.

I have an interface, let's call it Formatter();

public interface Formatter {
   public void format(Item item);

}

pretty self explanantory.

Problem is that I want Item itself to be an interface because
implementors of Formatter will want to deal with their more specific
types if Item's. So I am forced to classcast to those more specific
types of Item's in the implementing classes of Formatter, which sends
up a red flag to me.

How else can I do this?


Generics might help here:

public interface Formatter<T> {
  public void format (T value);
}

However, I suspect you have a deeper design problem that this will
merely move around. Do you actually need all formatters for distinct,
non-overlapping value types to share a common interface? Why? Expand
a bit on how you're planning on using this and maybe there's a better
way :)

-O


I agree, Generics should help with the current design, but what is your
goal*? Can you just put a "format" method on the Item interface?

* Goal as defined by "I want to provide X for the end user"

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