Re: Can this callback mechanism be generified?

From:
Casper Bang <casper@jbr.dk>
Newsgroups:
comp.lang.java.help
Date:
Sat, 03 May 2008 03:45:00 +0200
Message-ID:
<CsPSj.43798$ix.30981@weber.videotron.net>
Mark Space wrote:

This I still don't get. What's the advantage of Class<?> over Class?

I like your original program better. All the random generics are just
starting to obscure the actual design now.


I understand what you mean, but if you view it from a consumers (of the
API) point of view, I think it makes sense. I went from the old Java 1.0
way:

installCallback( Date.class, new Callback(){
         public String format(Object obj)
         {
             Date date = (Date)obj;
             return SimpleDateFormat.getInstance().format(date);
         }
     });

....to this, where the type of my callback definition flows over to
become the argument of the callback (thanks again Daniel) and gives me
more type-safety and allows NetBeans to create the anonymous inner class
with no need of casting:

installCallback( Date.class, new Callback<Date>(){
         public String format(Date date) {
             return SimpleDateFormat.getInstance().format(date);
         }
     });

....to the final version, where the type of my callback is extracted
rather than having to be supplied explicitly:

installCallback( new Callback<Date>(){
         public String format(Date date) {
             return SimpleDateFormat.getInstance().format(date);
         }
     });

Without closures, I think that's as clean as I can get it. Only rough
edge appears to be the way I extract the type from Callback.

/Casper

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