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Groups > comp.lang.java.programmer > #22254
| Newsgroups | comp.lang.java.programmer |
|---|---|
| Date | 2013-02-09 11:10 -0800 |
| References | <3c0d69c3-591d-4d99-8c13-30a0fd1684b3@googlegroups.com> <510db1c3$0$282$14726298@news.sunsite.dk> <510ea3f6$0$9502$9b4e6d93@newsspool1.arcor-online.net> <5115d723$0$295$14726298@news.sunsite.dk> |
| Message-ID | <6eb80ab4-30fb-4137-b7e0-1dcca2ca7fbc@googlegroups.com> (permalink) |
| Subject | Re: Design Patterns |
| From | Lew <lewbloch@gmail.com> |
Arne Vajhøj wrote:
> A plain nested class does not have access to the local
> variables.
>
> If that is not needed then fine.
>
> If that is needed then it has to be either a local
> or anonymous class.
Nitpick: or inner class.
> And local classes are very rare in the real world.
Sort of. Named local classes are indeed rare. Anonymous local classes
are rather common.
public List<File> getFiles()
{
final FileFilter filter = new FileFilter()
{
@Override boolean accept(File f) { return f.isDirectory(); }
};
// instance of an anonymous local class implementing FileFilter
...
}
This is good Java idiom because the 'FileFilter' instance is GCable when
done. It hasn't got state so its cost is virtually nil. So the local class
feature gives you good control of a program's memory requirements.
In less educated programmers' code I've seen such implementors scoped at
instance or even (gasp) static member level. And then people wonder at the
heap requirements.
Java has a funky and nuanced type structure. If you take advantage of
the nuances you get a lot in return.
It helps to use JLS (Java Language Specification) terminology in its
exact, narrowest framing. Really. Some call all nested classes "inner"
classes. Nope. And anonymous classes can be member or local types. It's
all about scope and context.
The JLS has a detailed treatment, and somewhere out there floats a
brilliant infographic going back to 1.2-ish days, but here's a brief
taxonomy.
top level * {public, package},
nested {static, inner {member, local}} * {any access}
This is off the top of my head, so any corrections welcomed.
There's a lovely corner case involving
public class Containing
{
private void doSomething() {...}
public class Within extends Containing
{
// @Override // ?
public void doSomething()
{
Containing.this.doSomething();
// super.doSomething(); // ?
...
}
}
}
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Design Patterns dougmmika@gmail.com - 2013-02-02 16:17 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 19:39 -0500
Re: Design Patterns Marcel Müller <news.5.maazl@spamgourmet.org> - 2013-02-03 18:52 +0100
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-03 14:23 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:57 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 11:10 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-09 19:36 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:44 -0800
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-09 23:47 -0800
Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-10 12:28 -0500
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:35 -0500
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-10 13:36 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-10 23:12 -0800
Re: Design Patterns "John B. Matthews" <nospam@nospam.invalid> - 2013-02-09 19:45 -0500
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-02 20:17 -0500
Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 19:43 -0800
Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-02 20:54 -0800
Re: Design Patterns Doug Mika <dougmmika@gmail.com> - 2013-02-02 21:11 -0800
Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-03 08:24 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:41 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-02 21:57 -0800
Re: Design Patterns Roedy Green <see_website@mindprod.com.invalid> - 2013-02-03 06:38 -0800
Re: Design Patterns Joerg Meier <joergmmeier@arcor.de> - 2013-02-04 17:06 +0100
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 12:38 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:31 -0500
Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-04 21:03 -0800
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-04 21:25 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:54 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 17:51 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:54 -0500
Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-05 09:43 +0000
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:03 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:09 -0500
Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 13:56 -0800
Re: Design Patterns markspace <markspace@nospam.nospam> - 2013-02-05 14:30 -0800
Re: Design Patterns Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-05 14:33 -0800
Re: Design Patterns lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-06 09:03 +0000
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:07 -0500
Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 09:10 -0500
Re: Design Patterns Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-05 13:20 -0500
Re: Design Patterns Lew <lewbloch@gmail.com> - 2013-02-05 13:10 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:11 -0500
Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-05 09:53 -0800
Re: Design Patterns Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-05 20:17 -0400
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 19:50 -0500
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 20:34 -0500
Re: Design Patterns Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-02-06 08:40 -0800
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:38 -0500
Re: Design Patterns Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 21:41 -0500
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