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Groups > comp.lang.java.programmer > #2906
| From | Tom Anderson <twic@urchin.earth.li> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: calling own methods from constructor |
| Date | 2011-04-06 23:06 +0100 |
| Organization | Stack Usenet News Service |
| Message-ID | <alpine.DEB.2.00.1104062255160.1512@urchin.earth.li> (permalink) |
| References | <slrnippkd9.phi.avl@gamma.logic.tuwien.ac.at> |
On Wed, 6 Apr 2011, Andreas Leitgeb wrote:
> Is there any *good* use of having the constructor call a method that
> actually *can* be overridden in a subclass? I mean, are there
> (non-anti)patterns of explicitly allowing subclasses to hook into
> base-class's construction?
public abstract class Library {
private List<Document> documents;
protected Library() {
documents = new ArrayList<Document>();
Collection<String> titles = listDocuments();
for (String title: titles) {
Document doc = loadDocument(title);
// do other preparatory stuff with the document
documents.add(doc);
}
}
protected abstract Collection<String> listDocuments();
protected abstract Document loadDocument(String title);
}
public class FilesystemLibrary extends Library {
// ...
}
public class WebDavLibrary extends Library {
// ...
}
public class JCRLibrary extends Library {
// ...
}
What are the alternatives?
The obvious one is for the subclass constructor to prepare all the objects
and pass them upward; i think that is likely to lead to a lot of
duplication of effort.
The almost as obvious one is to push the abstract methods out into a
separate interface - DocumentStore, say - and have the subclass
constructor pass up an instance of that.
You could also push the repeated logic out into some sort of factory or
helper, and have the subclasses call that, rather than relying on code in
the supeclass, but that is repetitive, and does nothing to establish
invariants in the superclass.
tom
--
Science which is distinguishable from magic is insufficiently advanced
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calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-06 20:48 +0000
Re: calling own methods from constructor Tom Anderson <twic@urchin.earth.li> - 2011-04-06 23:06 +0100
Re: calling own methods from constructor Lew <noone@lewscanon.com> - 2011-04-06 18:24 -0400
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 08:44 +0000
Re: calling own methods from constructor Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 04:14 -0700
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 12:32 +0000
Re: calling own methods from constructor Robert Klemme <shortcutter@googlemail.com> - 2011-04-07 05:55 -0700
Re: calling own methods from constructor Lew <lew@lewscanon.com> - 2011-04-07 08:10 -0700
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 20:31 +0000
Re: calling own methods from constructor Lew <lew@lewscanon.com> - 2011-04-07 14:10 -0700
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 22:15 +0000
Re: calling own methods from constructor Lew <noone@lewscanon.com> - 2011-04-07 21:22 -0400
Re: calling own methods from constructor Tom Anderson <twic@urchin.earth.li> - 2011-04-07 23:08 +0100
Re: calling own methods from constructor Lew <noone@lewscanon.com> - 2011-04-07 21:24 -0400
Re: calling own methods from constructor "Mike Schilling" <mscottschilling@hotmail.com> - 2011-04-09 22:06 -0700
Re: calling own methods from constructor Tom Anderson <twic@urchin.earth.li> - 2011-04-07 23:10 +0100
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 22:24 +0000
Re: calling own methods from constructor Lew <noone@lewscanon.com> - 2011-04-07 07:19 -0400
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 12:24 +0000
Re: calling own methods from constructor Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-04-06 20:46 -0400
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 08:36 +0000
Re: calling own methods from constructor Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-04-07 07:16 -0300
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 11:26 +0000
Re: calling own methods from constructor Paul Cager <paul.cager@googlemail.com> - 2011-04-07 03:20 -0700
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 11:36 +0000
Re: calling own methods from constructor Owen Jacobson <angrybaldguy@gmail.com> - 2011-04-06 22:23 -0400
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 09:13 +0000
Re: calling own methods from constructor Tobias Blass <tobiasblass@gmx.net> - 2011-04-07 10:58 +0000
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 12:19 +0000
Re: calling own methods from constructor Alessio Stalla <alessiostalla@gmail.com> - 2011-04-07 10:40 -0700
Re: calling own methods from constructor Tobias Blass <tobiasblass@gmx.net> - 2011-04-07 19:00 +0000
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 20:11 +0000
Re: calling own methods from constructor Jim Janney <jjanney@shell.xmission.com> - 2011-04-07 14:36 -0600
Re: calling own methods from constructor Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-04-07 20:59 -0400
Re: calling own methods from constructor Jim Janney <jjanney@shell.xmission.com> - 2011-04-07 10:26 -0600
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 20:16 +0000
Re: calling own methods from constructor Lew <lew@lewscanon.com> - 2011-04-07 14:05 -0700
Re: calling own methods from constructor Jim Janney <jjanney@shell.xmission.com> - 2011-04-07 16:15 -0600
Re: calling own methods from constructor Lew <noone@lewscanon.com> - 2011-04-07 21:28 -0400
Re: calling own methods from constructor Owen Jacobson <angrybaldguy@gmail.com> - 2011-04-07 23:21 -0400
Re: calling own methods from constructor Owen Jacobson <angrybaldguy@gmail.com> - 2011-04-07 23:39 -0400
Re: calling own methods from constructor Owen Jacobson <angrybaldguy@gmail.com> - 2011-04-07 23:58 -0400
Re: calling own methods from constructor Tom Anderson <twic@urchin.earth.li> - 2011-04-08 20:32 +0100
Re: calling own methods from constructor Tom Anderson <twic@urchin.earth.li> - 2011-04-07 23:05 +0100
Re: calling own methods from constructor Jim Janney <jjanney@shell.xmission.com> - 2011-04-07 17:38 -0600
Re: calling own methods from constructor Roedy Green <see_website@mindprod.com.invalid> - 2011-04-07 03:20 -0700
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-07 11:32 +0000
Re: calling own methods from constructor Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-08 01:51 +0200
Re: calling own methods from constructor Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-08 01:56 +0200
Re: calling own methods from constructor Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-04-08 09:30 +0000
Re: calling own methods from constructor Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-08 20:02 +0200
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