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NNTP-Posting-Date: Fri, 08 Apr 2011 00:37:49 -0500
Date: Thu, 07 Apr 2011 22:37:57 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Why only public methods on interfaces?
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On 4/7/2011 10:01 PM, Owen Jacobson wrote:
> On 2011-04-08 00:49:02 -0400, Patricia Shanahan said:
>
>> On 4/7/2011 5:09 PM, kramer31 wrote:
>>> Could someone please explain to me the rational behind only allowing
>>> public methods on interfaces? In my mind, protection and interfaces
>>> are two independent if perhaps somewhat related concepts.
>>
>> I think the original Java design underestimated the extreme usefulness
>> of Java interfaces. At the time one of their uses, representing the
>> public face of a package, was assumed to be the only possible use.
>>
>> I've wanted to use intra-package interfaces, containing only default
>> access methods. There is an unpleasant choice between making something
>> that should be an interface into an abstract class or having public
>> methods that are supposed to only be used within one package.
>
> As Stefan pointed out, interfaces themselves don't have to be public.
> This is legal:
>
> package com.example;
>
> interface SomeInternalAbstraction {
> public void flog(Horse horse);
> }
>
> -o
>

Yes, but then the implementing methods do have to be public, which is
undesirable if they should not be used outside the package.

Patricia