list literal gotcha and suggestion

[Reinier Zwitserloot]

Will you stop beating around the bush? What is it then?

What will this code print, and will the call to test() take O(1) or  
O(n) time?


public class Test {

     public void test(Collection<?> t) {
         System.out.println(t.size());
         System.out.println(t.contains("Hello"));
     }

     public static void main(String[] args) {
         test({"a", "b", "c", "a", "b", "c", /* 99,993 more strings  
*/, "Hello"});
     }
}


Will it take O(N) time and print '100000\ntrue\n', or will it take  
O(1) time and print '99997\ntrue\n'?

is this legal:

int x = 0;

{"a", "b"}.get(x)?


if it is, what new compiler magic will figure out that this literal  
must evidently be referring to a List, due to the get() call tacked on  
to it?




  --Reinier Zwitserloot



On 2009/07/10, at 18:00, Neal Gafter wrote:

> On Wed, Oct 7, 2009 at 8:55 AM, Reinier Zwitserloot <reinier at zwitserloot.com 
> > wrote:
> So, when passing {1, 2, 3} to a method that takes 1 Collection, it  
> will not, in fact, work without an explicit cast, then. Okay. As I  
> said, I think that's quite a serious use case.
>
> Correction: when passing {1, 2, 3} to a method that takes 1  
> Collection, it will, in fact, work without a cast.
>
> Before you suggest that, then, the construct will default to a List  
> - I'm not sure that's a good idea
>
> I'm suggesting that there be no such default.