Re: Can this callback mechanism be generified?

Casper Bang <>
Mon, 05 May 2008 04:01:44 +0200
Mark Space wrote:

I agree this part is easier to read, I just don't see the rest of the
code much improved (pulling the type by name from the interface name was
a pretty good trick. With luck, we'll get reifiable types in Java 7 and
then nonsense like that will be unneeded.)

I did some reading (Java Generics and Collections) and it turns out
there are ways to get to the types, in spite of erasure. So now I do it
a bit cleaner, no pulling apart a string and no reflection required:

private <T> Class extractGenericType(Callback<T> callback)
     Type[] interfaces = callback.getClass().getGenericInterfaces();

     if(interfaces.length != 1 || !(interfaces[0] instanceof
         throw new RuntimeException("You must supply a generified
Callback with a single parameterized type");

     Type[] parmTypes =

     return (Class)parmTypes[0];

I might be off base here, I haven't had a need to play around with
generic beyond basic functions, so please take this as discussion, not

Of course. :) Thanks a lot for the feedback!

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