varargs and boxing

[Guru dhaasan]

in the following code:

class varArg{
static void wide_varArg(Long... x){System.out.println("LONG");}
static void box_varArg(Integer... x){System.out.println("INTEGER");}

public static void main(String at[]){
int i=5;
wide_varArg(5,5);
box_varArg(i,i);
}
}


the compilation fails with the following message
varArg.java:7: wide_varArg(java.lang.Long...) in varArg cannot be applied to (int,int)
wide_varArg(5,5);
^
1 error



What is the error here ???

[Nik Arora]

Hi,
the compilation fails with the following message
varArg.java:7: wide_varArg(java.lang.Long...) in varArg cannot be applied to (int,int)
wide_varArg(5,5);

wide_varArg method takes Long wrapper type.When you call method like
wide_varArg(5,5) it will be boxed to Integer wrapper type and compiler will try to widen it into Long wrapper type here the error will get generated because Wrapper type of one cannot be widen to another wrapper type.


Regards
Nik

[dhwani mathur]

well!!below shown is the link which has two topics you refer to the first topic.

1)Using the Varargs Language Feature

It consist of the same problem as explained by you as well as the explanation for it but you will have to read it completly.
So here is the link.

http://java.sun.com/developer/JDCTechTips/2005/tt0104.html

i hope it helps you.

[Chandra Bhatt]

Hi,

primitive will be boxed to corresponding wrapper and then widening is done.
Integer can't widen to Long. As Nikhil said one wrapper can't widen from
one to another.

Integer can widen to Number or Object but not to any wrapper.


Thanks,

[Guru dhaasan]

Thanks Nik

[Guru dhaasan]

Thanks Chandra

[Guru dhaasan]

Thanks dhwani

The link was wonderful