using method handles to get array length

[Jochen Theodorou]

Hi,

is there a way to get the length of an array using method handles? Of
course I can write a small method to do that, but given the multitude of
primitive types this means a lot of small methods. So I was wondering if
there is a more elegant but still fast solution

bye Jochen

--
Jochen "blackdrag" Theodorou - Groovy Project Tech Lead
blog: http://blackdragsview.blogspot.com/
german groovy discussion newsgroup: de.comp.lang.misc
For Groovy programming sources visit http://groovy-lang.org

[Julien Ponge]

Hi Jochen,

How about:

lookup.findStatic(Array.class, "getLength", methodType(int.class, Object.class))

(java.lang.reflect.Array)

That's what we use in Golo to provide "length/size" methods to arrays, e.g.:

let a = [1, 2, 3]
println(a: length())

- Julien

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[Jochen Theodorou]

Hi Julien,

https://bugs.openjdk.java.net/browse/JDK-8051447 suggests that the
performance of this method is not the best... though it suggest an
equally generic alternative, with which I may go. so thanks for the idea

bye Jochen

[Julien Ponge]

Otherwise I'd say: generate all Object[] and primitive[] static methods that return you the length, then have method handles to them :-)

[Attila Szegedi]

Hm. Dynalink (and by extension, Nashorn) uses a method handle to Array.getLength(); maybe I'll rework it this way.