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Groups > comp.lang.java.programmer > #12543

Re: Aspect questions?

From Novice <novice@example..com>
Newsgroups comp.lang.java.programmer
Subject Re: Aspect questions?
Date 2012-02-29 21:31 +0000
Organization Your Company
Message-ID <XnsA008A84123C55jpnasty@94.75.214.39> (permalink)
References (17 earlier) <jigom7$e1d$1@news.albasani.net> <XnsA006B6A5992DDjpnasty@94.75.214.39> <jihabg$3oo$1@news.albasani.net> <XnsA008660779DFEjpnasty@94.75.214.39> <jilopr$lof$1@news.albasani.net>

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Lew <noone@lewscanon.com> wrote in news:jilopr$lof$1@news.albasani.net:

> Novice wrote:
>> And I need to look at List
>                              <E>
>> and ArrayList
>                 <E>
>> in more detail too. I've already
>> glanced at them and expect to start a thread on Interfaces [sic] soon
>> so that I can hash out some of my conceptions and misconceptions
>> about interfaces vs. classes. It might take a couple of days because
>> I've got some other things that I need to do first....
> 
> I favor a style of programming I call "type-based programming" that
> relies on interfaces and generics.
> 
> Since you say you write comments first, this should be natural for
> you. 
> 
> An interface is like a compilable comment that specifies what classes
> are supposed to accomplish. Classes are specific implementations of
> what their interfaces promise.
> 
> In general, per the advice of /Effective Java/ (2nd ed.) by Joshua
> Bloch* and other wise people, you should declare variables, return
> types, etc., as the most general (closest to interface) type that
> promises what you need. 
> 
> If all your list needs is what's promised by 'List<E>', you declare
> the type as the interface type. If it needs additional methods or
> attributes declared by 'ArrayList<E>' but not in the interface, you
> use the more specific type. If you don't even need the "listiness" but
> just that it's a collection, declare the type 'Collection<E>'.
> 
> When you design a program, design it in terms of interfaces. Defer 
> implementations as far as makes sense. This lets you focus on _what_
> the program should do rather than _how_.
> 
> I frequently write interfaces even when I'm only writing one
> implementing class. 
> 
> So taking lists as the example:
> 
>   List<String> options = new ArrayList<>();
> 
> I declared the 'options' variable as a 'List<String>', not as an 
> 'ArrayList<String>'. If I discover that the array-backed list wasn't
> giving me the performance or other implementation-specific behavior I
> need, but a linked list does, I can refactor more easily:
> 
>   List<String> options = new LinkedList<>();
> 
> The rest of the program, depending only on the "list"ness and not the 
> "array"ness, is unharmed.
> 
> (What performance differences are there? Excellent question! Pop quiz
> - please answer this post with your answer - where would you find out
> about performance characteristics of 'ArrayList<E>' and
> 'LinkedList<E>'?) 
> 
> Summary:
> Interface: what to do
> Class:     how to do it
> 

I need to understand what you've said a bit better before I try the pop 
quiz ;-) 

It makes perfect sense to me to figure out what a program needs to do 
before you worry about how it gets done. You've got to design a house - how 
many bedrooms, how many bathrooms, what style of house (ranch or bungalow 
or apartment building), etc. etc. - before you choose the exact fixtures. 

But when you talked about designing interfaces, I assumed you meant NEW 
interfaces. Your examples seem to be about selecting which of the existing 
interfaces - which kind of lists - you wanted. But those kinds already 
exist so you're really just choosing them, not inventing new ones to do new 
things. It would be helpful to me if you also talked about new interfaces 
and how those come about at design time.

By the way, I completely see your point in the examples. I have already 
benefited from the same by using Collections. I use more Sets than Lists 
and I will often start with a HashSet but if I start using it and find it 
doesn't have things in the order I wanted, it's a trivial thing to change 
it to another ordering by choosing a TreeSet or LinkedHashSet. That is 
REALLY convenient. 

Now that I think about it, I suppose I know enough to tackle the pop quiz 
after all. 

I have the feeling that I'm supposed to answer with something like "the 
API" or maybe based on something you said in one of your posts. Well, I'm 
going to "over-answer" the question and say this: 

I know that the API or the various Java Tutorials (like the one on 
Collections) often gives clues about performance and tells you explicitly, 
for example, that a HashSet normally performs best and a TreeSet worst with 
a LinkedHashSet typically performing almost as well as a HashSet. So that's 
obviously a good place to start. 

But you can obviously go a lot further. Various options come to mind:
- Simply try executing a few different implementations. This is worthwhile 
especially if it is a matter of changing just one line of code to get an 
alternate implementation. It might be completely impractical if we're 
talking about developing hundreds or thousands of lines of code to get 
another implementation. 
- Ask other people. If you have doubts about a given approach, ask on 
newsgroups like this one what their experience has been. The veterans here 
can probably tell you from personal experience that Approach A is awful and 
Approach B is much better and Approach C is even better.
- Fire up your debugger and try tracing through your implementation to see 
how efficient it seems. You can sometimes find bottlenecks that way that 
convince you to try a different approach.
- Performance tools. I have very little experience with these but I've 
heard whispers that there are tools you can apply to get real numbers as 
your program runs so that you can see if it is a pig. I expect the better 
tools in this category will even suggest changes to your code (or 
environment) to improve performance and maybe even make those changes for 
you. 
- Benchmarking. Set up your own benchmark to compare different 
implementations that solve a problem. Potentially lots of work involved but 
might be necessary if all else fails.

Okay, back to you.... ;-)
-- 
Novice

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Aspect questions? Novice <novice@example..com> - 2012-02-24 20:10 +0000
  Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-24 13:05 -0800
    Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 05:47 +0000
      Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-24 23:40 -0800
        Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 17:02 +0000
          Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-25 12:08 -0800
            Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 22:12 +0000
              Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-25 14:27 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 23:29 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 18:33 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 14:38 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 10:49 -0500
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 10:53 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 18:17 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-25 16:01 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 17:22 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 12:25 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 21:08 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 18:33 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 17:05 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 20:18 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 21:29 -0800
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-27 05:44 -0400
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 21:37 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-28 00:04 -0800
                Re: Aspect questions? Patricia Shanahan <pats@acm.org> - 2012-02-28 01:39 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 14:54 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-28 17:24 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 04:53 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:08 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 05:12 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 21:38 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 17:27 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-27 12:22 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 22:50 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-27 17:24 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 15:00 +0000
                Re: Aspect questions? Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-02-29 09:14 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-29 09:55 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 21:31 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-29 23:06 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-02 04:33 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-04 23:00 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-04 17:07 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-05 15:33 +0000
                JavaDoc linking (Was: Aspect questions?) Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-05 08:38 -0800
                Re: JavaDoc linking (Was: Aspect questions?) Novice <novice@example..com> - 2012-03-05 17:40 +0000
                Re: JavaDoc linking (Was: Aspect questions?) Patricia Shanahan <pats@acm.org> - 2012-03-05 21:25 -0800
                Re: JavaDoc linking (Was: Aspect questions?) Arne Vajhøj <arne@vajhoej.dk> - 2012-03-06 17:23 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-05 23:45 -0800
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-03-06 06:03 -0400
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-06 21:05 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:11 -0500
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:09 -0500
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-26 23:43 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 05:20 +0000
                Re: Aspect questions? Patricia Shanahan <pats@acm.org> - 2012-02-26 21:32 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 17:36 +0000
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 13:18 -0500
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 14:05 -0500
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 14:33 -0500
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 14:53 -0500
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 15:16 -0500
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-27 17:57 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 22:59 +0000
                Re: Aspect questions? Jeff Higgins <jeff@invalid.invalid> - 2012-02-28 05:50 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 15:03 +0000
                Re: Aspect questions? Patricia Shanahan <pats@acm.org> - 2012-02-27 13:17 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 22:55 +0000
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-27 05:58 -0400
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 18:14 +0000
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-28 00:12 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-28 02:04 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 21:22 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 15:11 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:14 -0500
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-28 23:09 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 15:25 +0000
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-01 00:22 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-01 01:44 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-29 23:24 -0800
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-01 21:19 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-02 01:52 +0000
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-03 01:39 +0000
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-05 15:38 +0000
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-05 22:50 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-05 23:46 -0800
                Re: Aspect questions? Patricia Shanahan <pats@acm.org> - 2012-03-06 08:14 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-06 21:23 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-08 20:10 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-02 01:49 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-01 22:38 -0800
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-03-02 06:05 -0400
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-02 14:25 +0000
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-03-02 18:10 -0400
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-02 14:12 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-02 08:57 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-05 15:57 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-05 23:48 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-03-07 20:33 +0000
                Re: Aspect questions? Lew <lewbloch@gmail.com> - 2012-03-07 13:09 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:20 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-03-02 14:28 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:16 -0500
                Re: Aspect questions? markspace <-@.> - 2012-02-26 10:10 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 20:52 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 13:48 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 13:47 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 18:40 -0500
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 18:36 -0500
                Re: Aspect questions? markspace <-@.> - 2012-02-26 16:04 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 19:38 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 17:09 -0800
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-26 20:08 -0400
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 19:43 -0500
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-27 22:03 -0400
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 21:18 -0500
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 13:43 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 01:11 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 21:49 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-27 18:37 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-27 12:28 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-28 00:55 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-27 17:37 -0800
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 15:57 +0000
                Re: Aspect questions? Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-02-28 03:21 -0600
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-28 09:19 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-27 21:12 -0500
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-28 05:59 -0400
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-28 17:27 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-29 16:07 +0000
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-03-02 17:26 -0500
              Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 18:22 -0500
                Re: Aspect questions? markspace <-@.> - 2012-02-25 20:22 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-25 22:20 -0800
                Re: Aspect questions? markspace <-@.> - 2012-02-26 00:04 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 00:21 -0800
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 00:33 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 10:43 -0500
                Re: Aspect questions? Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-26 11:18 +0000
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-26 11:04 -0400
                Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-26 10:22 -0400
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 21:04 +0000
                Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-26 14:01 -0800
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 18:46 -0500
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 09:50 -0500
                Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 10:38 -0500
                Re: Aspect questions? Novice <novice@example..com> - 2012-02-26 20:49 +0000
      Re: Aspect questions? jlp <jlp@jlp.com> - 2012-02-25 09:47 +0100
        Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 17:03 +0000
          Re: Aspect questions? jlp <jlp@jlp.com> - 2012-02-25 20:02 +0100
      Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-25 10:20 -0400
        Re: Aspect questions? markspace <-@.> - 2012-02-25 08:18 -0800
          Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 12:04 -0500
        Re: Aspect questions? Novice <novice@example..com> - 2012-02-25 17:17 +0000
          Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-25 18:40 -0400
          Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 18:18 -0500
      Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 09:21 -0500
      Re: Aspect questions? Roedy Green <see_website@mindprod.com.invalid> - 2012-02-25 14:35 -0800
  Re: Aspect questions? markspace <-@.> - 2012-02-24 14:30 -0800
    Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-24 19:47 -0500
      Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-24 20:52 -0800
        Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-25 09:31 -0500
        Re: Aspect questions? Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-02-25 11:05 -0400
          Re: Aspect questions? Lew <noone@lewscanon.com> - 2012-02-25 12:20 -0800
  Re: Aspect questions? Arne Vajhøj <arne@vajhoej.dk> - 2012-02-24 19:00 -0500
  Re: Aspect questions? Tom Anderson <twic@urchin.earth.li> - 2012-02-25 00:22 +0000

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