Re: Generics Warnings yet again

From:
=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 26 Jul 2008 22:19:17 -0400
Message-ID:
<488bdb25$0$90265$14726298@news.sunsite.dk>
Roedy Green wrote:

Is it possible to write code with this meaning without compiler
warning messages? Where Macro is the name of an interface.

I understand the code is just using a plain Class object, and hence as
no idea if forName actually returned a Class object that implements
Macro. I am using the cast here is the C++ , "trust me" sense.
Ideally I would like the cast to fail if the class does not implement
Macro.

 // e.g. "com.mindprod.htmlmacros.Measure"
 final Class<Macro> macroClass = ( Class<Macro> ) Class.forName(
packageName + "." + macroName );

     
 [javac] E:\com\mindprod\htmlmacros\LoadCodeToProcessMacro.java:130:
warning: [unchecked] uncheck
cast
 [javac] found : java.lang.Class<capture#419 of ?>
 [javac] required: java.lang.Class<com.mindprod.htmlmacros.Macro>
 [javac] final Class<Macro> macroClass = ( Class<Macro> )
Class.forName( packageName
." + macroName );

The other way of asking this is, what is the best practice in this
ugly situation?


Due to type erasure then that cast will never fail.

When you try and do the matching cast on an instance, then it will fail.

Arne

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