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From: Owen Jacobson <angrybaldguy@gmail.com>
Newsgroups: comp.lang.java.programmer
Message-ID: <2011040801014026003-angrybaldguy@gmailcom>
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Subject: Re: Why only public methods on interfaces?
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NNTP-Posting-Date: Fri, 08 Apr 2011 05:01:40 UTC
Date: Fri, 8 Apr 2011 01:01:40 -0400
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:2980

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