Collections.sort in 1.5

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Myriam Abramson - 30 Aug 2006 03:47 GMT

I have:

Vector<MyClass> v = new Vector<MyClass>();

Collections.sort(v);

Now, MyClass implements Comparable but Collections.sort seems to
ignore it. I would think that the order coded in the compareTo method
in MyClass would be the natural order of instances of this class, no?
I had to create a Comparator class to tell Collections.sort how to
sort correctly. Why having those annotations if they are not picked up
correctly? Again I have Java 1.5. Thanks for any insights.

myriam

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hiwa - 30 Aug 2006 04:05 GMT

Myriam Abramson のメッセージ:

> I have:
>
[quoted text clipped - 10 lines]
>
> myriam

Your mplementation of equals() and hashCode() issue, or other
issue(s)...
Post a small demo code that is generally compilable, runnable and could
reproduce your problem. See:
http://homepage1.nifty.com/algafield/sscce.html

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Patricia Shanahan - 30 Aug 2006 06:21 GMT

> I have:
>
[quoted text clipped - 8 lines]
> sort correctly. Why having those annotations if they are not picked up
> correctly? Again I have Java 1.5. Thanks for any insights.

Interesting. There has to be something special going on here, because
Collections.sort normally deals correctly with Comparable. I second the
request for a short, self-contained, compilable example.

I can think of some explanations, but they depend on how MyClass is
defined. For example, it could extend a Comparable class and not itself
provide a public compareTo(Object), only a compareTo(MyClass). In that
case, the sort would be according to the parent class natural order.

The quickest way to find out what is really going on will be an example.

Patricia

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Collections.sort in 1.5

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