Re: Collections.sort in 1.5

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 30 Aug 2006 05:21:19 GMT

Message-ID:

<jf9Jg.359$v%4.150@newsread1.news.pas.earthlink.net>

Myriam Abramson wrote:

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.

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