Groups > comp.lang.java.programmer > #3038

Re: Novice to Generics Trying to Implement a Generic Priority Queue

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From	Tom Anderson <twic@urchin.earth.li>
Newsgroups	comp.lang.java.programmer
Subject	Re: Novice to Generics Trying to Implement a Generic Priority Queue
Date	Mon, 11 Apr 2011 22:41:05 +0100
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On Mon, 11 Apr 2011, Daniele Futtorovic wrote:

> On 11/04/2011 21:10, KevinSimonson allegedly wrote:
>> On Apr 11, 11:52 am, r...@zedat.fu-berlin.de (Stefan Ram) wrote:
>>> KevinSimonson<kvnsm...@hotmail.com>  writes:
>>>> Exception in thread "main" java.lang.ClassCastException:
>>>> [Ljava.lang.Object; cannot be cast to [Ljava.lang.Comparable;
>>> 
>>> ( Da[] )new java.lang.Comparable[ size ]
>> 
>> Stefan, thanks!  That solved the problem and my program works just
>> fine now.
>
> This might be somewhat OK in this case, but it's hardly advisable.
>
> A Comparable[] /is not a/ Da[].
>
> You'd normally pass the Class object around in such cases:
>
>  public PriorityQueue( Class<Da> component, int size )
>    throws BadSizeException
>  {
>    if (0<= size)
>    { queue = (Da[]) Array.newInstance( component, size );

I'm not sure about 'normally'. That is certainly a known technique (for
those who haven't seen it, this use of a Class is called a 'type token'),
and whilst it may be advisable, i don't think it's more common than making
an array of some suitable static type and casting it uncheckedly [sic].
Does the JDK use it anywhere?

tom

-- 
Taking care of business

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Thread

Novice to Generics Trying to Implement a Generic Priority Queue KevinSimonson <kvnsmnsn@hotmail.com> - 2011-04-07 16:03 -0700
  Re: Novice to Generics Trying to Implement a Generic Priority Queue markspace <-@.> - 2011-04-07 17:32 -0700
    Re: Novice to Generics Trying to Implement a Generic Priority Queue KevinSimonson <kvnsmnsn@hotmail.com> - 2011-04-08 14:55 -0700
      Re: Novice to Generics Trying to Implement a Generic Priority Queue markspace <-@.> - 2011-04-08 15:54 -0700
        Re: Novice to Generics Trying to Implement a Generic Priority Queue Lew <noone@lewscanon.com> - 2011-04-08 20:39 -0400
          Re: Novice to Generics Trying to Implement a Generic Priority Queue Tom Anderson <twic@urchin.earth.li> - 2011-04-09 10:36 +0100
  Re: Novice to Generics Trying to Implement a Generic Priority Queue Roedy Green <see_website@mindprod.com.invalid> - 2011-04-09 05:50 -0700
    Re: Novice to Generics Trying to Implement a Generic Priority Queue KevinSimonson <kvnsmnsn@hotmail.com> - 2011-04-11 08:08 -0700
      Re: Novice to Generics Trying to Implement a Generic Priority Queue markspace <-@.> - 2011-04-11 10:29 -0700
      Re: Novice to Generics Trying to Implement a Generic Priority Queue KevinSimonson <kvnsmnsn@hotmail.com> - 2011-04-11 12:10 -0700
        Re: Novice to Generics Trying to Implement a Generic Priority Queue Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-11 21:42 +0200
          Re: Novice to Generics Trying to Implement a Generic Priority Queue Tom Anderson <twic@urchin.earth.li> - 2011-04-11 22:41 +0100
            Re: Novice to Generics Trying to Implement a Generic Priority Queue Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-04-12 01:07 +0200

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