Re: Comparable loses its interface powers.

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 24 Feb 2010 16:47:57 -0800

Message-ID:

<1Njhn.34558$K81.4577@newsfe18.iad>

On 2/23/2010 11:50 PM, Roedy Green wrote:

If Comparable were just an ordinary interface you could say things
like this:

Comparable a = "abc";
Comparable b = Double.valueOf ( 10.0d );
Comparable c = Double.valueOf ( 12.9d );

int x = b.compareTo( c );

But generics butt in and it seems to be impossible to keep around
arrays of Comparables for sorting columns.

Well, you wouldn't want to keep any kind of arrays around, use List<Foo>
or Collection<Foo> instead...

Now, if you have a generic sortable container, you would use
MyContainer<T extends Comparable<T>> as the declared type, so that you
could have StringColumn implements MyContainer<String>.

One way, which I find ugly is to sort Objects instead of Comparables
then cast them to specific types before calling compareTo. That should
not be necessary. All the JVM should need to know at compile time is
that a reference is implements comparable.

Yes, but at compile time, wouldn't you prefer avoiding
ClassCastException from within compareTo?

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>