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Newsgroups: comp.lang.java.programmer
From: Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at>
Subject: Re: Style Police (a rant)
References: <j39fdc$1hi$1@dont-email.me> <j3akb0$61g$1@news.albasani.net> <MPG.28d509bfb828d36d9896ad@202.177.16.121> <slrnj6mj4j.6gl.avl@gamma.logic.tuwien.ac.at> <d056de37-3406-4ea1-950e-cd762fa35b6b@glegroupsg2000goo.googlegroups.com> <slrnj6pg53.6gl.avl@gamma.logic.tuwien.ac.at> <c49eeaae-647b-423e-820c-86221b6b9f21@glegroupsg2000goo.googlegroups.com> <slrnj6qh8n.6gl.avl@gamma.logic.tuwien.ac.at> <MPG.28d7673e2cb655989896bb@202.177.16.121>
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Date: 17 Sep 2011 19:56:21 GMT
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:8109

Wanja Gayk <brixomatic@yahoo.com> wrote:
> avl@gamma.logic.tuwien.ac.at says...
>> While a *non*-final List<String> typed variable could later be
>> assigned an instance of LinkedList<String>, a final can't.
>> It hardly ever hurts to have a final variable carry the most
>> specific subtype.
> final x = new Vector<String>();
> Enumeration e = x.elements();

> [ later someone changes it to ]

> final x = new LinkedList<String>();
> Enumeration e = x.elements(); <<- and breaks this and [...]

I think it's even a bonus that this would no longer compile.
On the other hand:

  final List<String> l = new Vector<String>();
  [...]
  // I know, I initialized l with a Vector just before:
  Vector<String> vec=(Vector<String>)l; // compiler cannot check
  Enumeration e = vec.elements();

wouldn't crash until Runtime, if l's initializer were changed to
LinkedList lateron...

> Abstraction is the whole point of declaring interfaces, you don't want 
> your code to be brittle.

But inconsequent abstraction is even much worse than just
forgetting about it altogether.

PS: Obviously, one cannot just idly change the initializer of a variable
  and expect it all to work. Not even without the currently discussed
  feature.