Forcing elements of List to be converted as java.lang.Long

[Attila Szegedi]

You're right about that, Rémi. However, even in Java you can twist things with unchecked casts so that you pass a List<Object> to this method and force it into a ClassCastException, so I'm not sure if us going out of our way to inject a suitable conversion would be desired.

On Nov 27, 2014, at 12:59 AM, Remi Forax <forax at univ-mlv.fr> wrote:

> 
> On 11/27/2014 12:37 AM, Tim Fox wrote:
>> Hi Attila,
>> 
>> I understand the generic type info is erased, but my question was whether there is any way I can "force" Nashorn to convert the elements as Long rather than Integer when doing the conversion, e.g. using some special Nashorn specific syntax, e.g.
>> 
>> var arr = [123];
>> arr.forceConversionAsLong = true; // A contrived example but you get the point :)
>> obj.foo(arr);
>> 
>> (or whatever)
> 
> BTW, generic info like this one are preserved because javac need them to cross compile.
> so nashorn could inspect the generic signature and if there is one try to do the suitable conversion.
> 
> Rémi
> 
>> 
>> 
>> On 26/11/14 21:50, Attila Szegedi wrote:
>>> I don't think so. As the types are erased at run time all we see is a method with signature foo(List list). I think if you tried to add two methods to a class:
>>> 
>>>     public void foo(List<Long> x) { }
>>>     public void foo(List<Integer> x) { }
>>> 
>>> then javac would refuse to compile it saying that both have the same erasure.
>>> 
>>> Attila.
>>> 
>>> On Nov 26, 2014, at 10:45 PM, Tim Fox <timvolpe at gmail.com> wrote:
>>> 
>>>> Hello folks,
>>>> 
>>>> I have a Java method:
>>>> 
>>>> public void foo(List<Long> list) {
>>>>  System.out.println("elem0 is " + list.get(0));
>>>> }
>>>> 
>>>> Which I call from JS with a JS array:
>>>> 
>>>> obj.foo([123]);
>>>> 
>>>> This results in a ClassCastException as Nashorn converts the JS Array into a java.util.List instance which contains a java.lang.Integer element (not java.lang.Long)
>>>> 
>>>> Is there any way to force Nashorn to convert the array elements as Longs not Integers?
>>>> 
>>>> Thanks.
>> 
>