new clone feature

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Roedy Green - 05 Feb 2006 01:46 GMT

There is supposed to be a way you can avoid the cast from clone.

What is the feature called and how do you use it.
There is apparently more to it that just saying

public Footprint clone()

instead of

public Object clone()

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Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

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Stefan Ram - 05 Feb 2006 01:59 GMT

>What is the feature called and how do you use it.
>There is apparently more to it that just saying
> public Footprint clone()
>instead of
>public Object clone()

»Note that this definition supports covariant returns -
that is, the specialization of the return type to a
subtype (but only for reference types).«

Java Language Specification, Third Edition,
8.4.5 Method Return Type

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Paul Tomblin - 05 Feb 2006 03:14 GMT

In a previous article, Roedy Green <my_email_is_posted_on_my_website@munged.invalid> said:

> public Footprint clone()

Maybe it's because I come from a C++ background, but I've always preferred
to make a copy constructor rather that rely on clone(). So I would write
Footprint myClone = new Footprint(myOldFootprint);
rather than
Footprint myClone = (Footprint)myOldFootprint.clone();

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Paul Tomblin <ptomblin@xcski.com> http://xcski.com/blogs/pt/
"If Bill Gates had a dime for every time a Windows box crashed...
.... Oh, wait a minute, he already does."

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Paul Tomblin - 05 Feb 2006 14:08 GMT

In a previous article, ptomblin+netnews@xcski.com (Paul Tomblin) said:

>In a previous article, Roedy Green
><my_email_is_posted_on_my_website@munged.invalid> said:
[quoted text clipped - 5 lines]
>rather than
> Footprint myClone = (Footprint)myOldFootprint.clone();

I should mention that I'm aware of the usefulness of the clone situation
where the item you're cloning might be one of several subclasses of the
"Footprint" and you want the new one to be the right one.

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Paul Tomblin <ptomblin@xcski.com> http://xcski.com/blogs/pt/
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new clone feature

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