Re: [Jython-users] List<Class<?>> types

[Jim B. <jb...@zy...>]

A few things that expand upon your original question:

1. A generic (or parameterized) class like List<Class<?>> will see type
erasure. As far as Jython, or any Java program is concerned, it's just a
List of Object. However, Java does do dynamic type checking here by using a
cast (implicitly added by the compiler if working with generics, you might
have thought it was just statically type checking!) to maintain type safety.

We can further just take advantage of how Jython can coerce parameters to
arrays; it's possible to pass a Python list to Java methods expecting
arrays:

java.util.Arrays.asList([42,9,1,0,5])

This is probably the way you want to use it, because it's simplest.

2. Java arrays do carry type information of what they contain - there is no
type erasure. To construct Java arrays, you can use either the array or
jarray module. I prefer to use the normal Python array module, but with the
extended support in Jython extension that you can use some class (aClass
here) instead of a typecode:

array.array(aClass [, iterable])

In either array or jarray, any such constructed arrays are just Java arrays
of aClass, with potential gains in efficiency and reduced overhead in
converting back & forth between Python and Java.

3. For the specific case of using a primitive for double you can either use:

a) array.array('d'[, iterable])
b) array.array(java.lang.Double.TYPE [, iterable])

with a) just translated to b) internally, so they are completely
equivalent, except that a) is normal Python, b) is the extended Jython
version.

- Jim


On Sun, Jul 28, 2013 at 6:43 AM, Eric Berryman <eri...@gm...>wrote:

> Hello!
>
> Is it possible to pass an object "List<Class<?>> types" from jython to
> java?  Maybe using jarray?
>
> ie.
> types.set(0, double.class);
> (note I would like to pass the primitive)
>
> Thank you!
> Eric
>
>
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