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Re: limitations on using enum as generic parameter

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On 02/11/2011 01:50 AM, Roedy Green wrote:
> On Tue, 8 Feb 2011 09:50:32 -0800 (PST), "dalamb@cs.queensu.ca"
> <david.alex.lamb@gmail.com>  wrote, quoted or indirectly quoted someone
> who said :
>
>> javac says "Cannot find symbol: method
>> values()".  (the reference to Enum.valueof later also gets errors,
>> which is why I commented it out to simplify the test).
>
> Even though enums are under the hood implemented as nested classes,
> the Java language does think of enums as being classes or inheriting
> from anything.  You are trying to use them as if they were ordinary
> classes.
>
> To pull that off you would have to re-invent enums as ordinary
> classes.  To do that, have a look at the various enum decompilations I
> have posted at http://mindprod.com/jgloss/enum.html

The 'enum' is a specialization of the "type-safe enumeration" with compiler 
support.  You can still implement type-safe enumerations by hand, just as 
Joshua Bloch described in edition one of /Effective Java/, before Java 5.

People forget that enumerations are not limited to 'enum' exactly because 
'enum' covers nearly all situations where you want a type-safe enumeration, 
but in the end 'enum' is syntactic sugar for the latter.  When 'enum' doesn't 
do the job you roll your own, just like you use a spelled-out 'for' when a 
for-each isn't enough.

-- 
Lew
Ceci n'est pas une fenêtre.
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|#/ * |   \#|
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||    |  * ||
|o *  |    o|
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Re: limitations on using enum as generic parameter Lew <noone@lewscanon.com> - 2011-02-11 07:40 -0500

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