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NNTP-Posting-Date: Fri, 06 May 2011 09:03:50 -0500
Date: Fri, 06 May 2011 07:03:37 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: "Program to an interface" - When to break a design pattern
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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