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Groups > comp.lang.java.programmer > #36674
| From | Eric Sosman <esosman@comcast-dot-net.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: How to assign an object to another in it method? |
| Date | 2017-06-19 10:22 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <oi8mfs$ies$1@dont-email.me> (permalink) |
| References | <oi5q4t$1okn$1@gioia.aioe.org> <factory-20170619011810@ram.dialup.fu-berlin.de> |
On 6/18/2017 8:47 PM, Stefan Ram wrote:
> parmenides <xparmenides@yahoo.com> writes:
>> Is there any way to do assigment as a whole in this
>> situation?
>
> The constructor can read the fields from the database:
>
> class Alpha
> {
> public Alpha()
> { /* read the fields from the database here */ }}
Although this is possible, it is often ill-advised to "do too
much work" in a constructor. One drawback is the difficulty in
extending such a class:
public class Beta extends Alpha {
public Beta() {
...
}
}
The problem here is that when a Beta is under construction, the
database activity occurs before the Beta instance is "ready."
That *may* be acceptable, but can also be dangerous. I'd suggest
that if you do "a lot" of work in a constructor, you should make
sure the class cannot be extended: make it `final', or make all
the constructors `private'.
> . Sometimes, a factory method might be more appropriate.
Agreed. Another approach is to use an initialization method:
public class Alpha {
public Alpha() {
// Do only a little work here
}
public init() {
// Read from the database
}
...
}
This can become a bit clumsy, though: You have to make sure that
init() is called exactly once, which means you probably need a
`private boolean hasBeenInitialized;' data member that most
other methods must test so they can throw IllegalStateException
if anything is amiss. Usually, Stefan's suggestion of a static
factory method calling a private constructor works more smoothly
and produces less clutter in the code.
--
esosman@comcast-dot-net.invalid
Thirteen hundred eleven days to go.
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How to assign an object to another in it method? parmenides <xparmenides@yahoo.com> - 2017-06-18 20:02 +0800
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-18 08:09 -0400
Re: How to assign an object to another in it method? Robert Klemme <shortcutter@googlemail.com> - 2017-06-18 15:31 +0200
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 10:22 -0400
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 08:13 -0700
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 11:53 -0400
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 09:06 -0700
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-19 13:56 -0400
Re: How to assign an object to another in it method? lewbloch@gmail.com - 2017-06-27 13:49 -0700
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-06-28 12:20 +0000
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-28 05:51 -0700
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-28 14:03 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-02 21:23 -0400
Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 10:59 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-03 08:38 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-03 14:04 +0000
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 10:39 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-03 16:28 +0000
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 16:52 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-03 22:04 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-03 23:15 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-04 21:46 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-04 22:18 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-08 21:13 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-08 22:12 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-11 17:56 +0000
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 15:40 -0400
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-11 13:49 -0700
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 17:41 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:27 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:43 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:49 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-12 17:20 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 10:08 +0000
Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 11:35 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 08:14 -0400
Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-13 14:29 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 13:47 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 18:09 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 15:01 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 19:19 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 15:39 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 16:49 +0000
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-13 10:24 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-13 17:19 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-13 21:17 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-14 06:40 +0000
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 14:26 -0400
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-15 14:36 +0000
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-14 12:10 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 14:40 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-14 14:51 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 21:05 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-14 21:06 -0400
Re: How to assign an object to another in it method? lewbloch@gmail.com - 2017-07-14 14:44 -0700
Re: How to assign an object to another in it method? Andreas Leitgeb <avl@logic.at> - 2017-07-12 16:23 +0000
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-07-12 10:12 -0700
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:16 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:46 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:52 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 20:24 -0400
Re: How to assign an object to another in it method? Jerry Stuckle <jstucklex@attglobal.net> - 2017-07-11 21:49 -0400
Re: How to assign an object to another in it method? Arne Vajhøj <arne@vajhoej.dk> - 2017-07-11 21:55 -0400
Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 12:37 +0000
Re: How to assign an object to another in it method? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-07-03 11:34 -0400
Re: How to assign an object to another in it method? Martin Gregorie <martin@address-in-sig.invalid> - 2017-07-03 17:28 +0000
Re: How to assign an object to another in it method? v_borchert@despammed.com (Volker Borchert) - 2017-06-19 17:13 +0000
Re: How to assign an object to another in it method? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-19 13:40 -0700
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