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From: Arved Sandstrom <asandstrom3minus1@eastlink.ca>
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Newsgroups: comp.lang.java.programmer
Subject: Re: "Program to an interface" - When to break a design pattern
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Date: Fri, 06 May 2011 17:30:14 -0300
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:3712

On 11-05-06 11:03 AM, Patricia Shanahan wrote:
> On 5/6/2011 3:24 AM, Arved Sandstrom wrote:
> ...
>> As far as your nuance is concerned, I'm interested (the _OP_ is
>> interested) in providing a map with predictable insertion order. Map
>> does not satisfy that; LinkedHashMap does. If I return Map then I am
>> making a mistake.
> ...
> 
> I think this is the key point.
> 
> Compare the following two rules:
> 
> 1. Program to an interface.
> 
> 2. Program to the least specific type that meets the requirements, with
> preference for interfaces.
> 
> Much of the time, the two rules give the same result. They differ in
> cases like this one, where there is no interface that meets the
> requirements. The second rule also helps with deciding which interface
> to use. If you only need a Set, don't specify a SortedSet.
> 
> Patricia

I agree wholeheartedly. #2 is the real rule. Prefer interfaces. In some
cases even consider writing your own interface and some adapters so that
a bunch of calling code sees an interface. But from time to time the
least specific type that meets the requirements is a concrete class.

AHS