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Groups > comp.lang.java.programmer > #29271

Re: generics array type check

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On 7/24/2014 4:03 AM, Philipp Kraus wrote:
> Hello,
>
> I have got this signature of a method private static <T> long[] getSize(
> T p_data )
> Depend on the type T the return value is changes e.g. on a non-array type
>
> getSize( 5 ) => new long[1]{1}
> getSize( "test" ) => new long[1]{1}
>
> on an array it should return
>
> double[] p_array
> getSize( p_array ) => new long[1]{ p_data.length }
>
> and on 2-dimensional array it should be
> double[][] p_array
> getSize( p_array ) => new long[2]{ p_array.length, p_array[0].length }
>
> How can I check the generic data type in a correct way to detect the
> array type?

     You can't, as far as I'm aware.

     However, you can use p_data.getClass().getComponentType() to
query the reference's actual (not generic) identity.  If it returns
null the reference is not to an array; if it's non-null you apply
getComponentType() recursively to descend through additional levels.

     If p_data is null I think you're out of luck.

-- 
esosman@comcast-dot-net.invalid

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generics array type check Philipp Kraus <philipp.kraus@flashpixx.de> - 2014-07-24 10:03 +0200
  Re: generics array type check Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-07-24 09:13 -0400
  Re: generics array type check markspace <markspace@nospam.nospam> - 2014-07-24 08:24 -0700
    Re: generics array type check Arne Vajhøj <arne@vajhoej.dk> - 2014-07-25 21:14 -0400
  Re: generics array type check Mike Amling <mamling@chaff.us> - 2014-07-25 12:15 -0500
    Re: generics array type check Mike Amling <mamling@chaff.us> - 2014-07-25 13:21 -0500
  Re: generics array type check Arne Vajhøj <arne@vajhoej.dk> - 2014-07-25 21:12 -0400

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