Re: hierarchy of interface/implementations.

From:
Lew <lew@lewscanon.com>
Newsgroups:
comp.lang.java.programmer
Date:
Tue, 24 Mar 2009 15:08:25 -0700 (PDT)
Message-ID:
<68c71d62-368d-4bf0-9ec7-cc1c2b6da1dc@z9g2000yqi.googlegroups.com>
On Mar 24, 5:29 pm, horo...@gmail.com wrote:

I had a quick question about implementing interfaces and storing those
implementations..

suppose I have a implementation that I defined:

package mycom;

public interface MyInterface
{
     public void mymethod();

}

and I put it in file:

mycom/MyInterface.java

and I want to have several different implementations defined for it,
that I want to stick under:

mycom/MyInterface/Implentation1.java
mycom/MyInterface/Implentation2.java
mycom/MyInterface/Implentation3.java

Can you do this? when I go to make my Implementation1, I say:

package mycom.MyInterface;

I get a conflict, apparently with the interface. But this seems the
logical way to structure things. My workaround is to make a directory:

mycom/MyInterfaceImpl

and stuff all implementations there, but this IMO is a hack and I'm
hoping that there are other ways around this (that make sense, camel
case promotes spelling errors, isn't compiler checkable, etc.)


Drop the upper-case letters to lower-case in the package name. That's
more conventional, and will avoid a conflict with type names, which by
convention must have upper-case letters in them.

Forget directories - think in terms of packages and types, then work
out the directories after the fact.

You have more flexibility with names if you have a two-level domain
followed by functional package names.

One-level domain (per your example):

  mycom.MyInterface
  mycom.impl.Implentation1
  mycom.impl.Implentation2
etc.

"MyInterface", "impl" and "ImplementationN" are far too general and
semantically useless names to really show the power, though.

Two-level domain, e.g., lewscanon.com, for a product known as "Killer
App":

 com.lewscanon.killerapp.Potable;
 com.lewscanon.killerapp.potable.Water;
 com.lewscanon.killerapp.potable.Juice;
 com.lewscanon.killerapp.potable.Whiskey;

Another way, more structurally bound to the code:

 com.lewscanon.killerapp.potable.Potable;
 com.lewscanon.killerapp.potable.impl.Water;
 com.lewscanon.killerapp.potable.impl.Juice;
 com.lewscanon.killerapp.potable.impl.Whiskey;

And the way I usually prefer:

 com.lewscanon.killerapp.potable.Potable;
 com.lewscanon.killerapp.potable.Water;
 com.lewscanon.killerapp.potable.Juice;
 com.lewscanon.killerapp.potable.Whiskey;

--
Lew

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