overloads for java.util.RandomAccess

[Gernot Neppert]

Sorry, googlemail interpreted some key that I pressed (I don't know which
one, unfortunately) to send the previous mail without my intent...
I continue here:

So, I suggest to replace it with the following overload which takes the
established approach of testing for 'RandomAccess' explicitly:

 public static <T> Stream<T> stream(List<T> source) {
    if(source instanceof RandomAccess) {
        return new ValuePipeline<>(new
RandomAccessListStreamAccessor<T>(source));
    }
    return new ValuePipeline<>(new TraversableStreamAccessor<>(source,
source.size()));
}


As you can see, I've also implicitly changed the type parameter(s) of
'RandomAccessListStreamAccessor' so that it works on java.util.List
directly.

(Note: The current version has a performance issue, as the erased argument
type is not java.util.List, but rather java.util.RandomAccess, and there's
an invisible checked cast involved in every single invocation of any of
List's methods. Probably not what the author intended)







2012/10/31 Gernot Neppert <mcnepp02 at googlemail.com>

> Hello all,
>
> while trying to get an overview of the various factory methods in
> java.util.streams.Streams, it grabbed my attention that the 'tagging
> interface' java.util.RandomAccess has been chosen there as an overload
> discriminator. I think that's a premiere in the entire JDK!
>
> Take a look at this one, for example:
>
>     public static <T, L extends RandomAccess & List<T>> Stream<T> stream(L
> source) ;
>
> This overload will obviously only be picked by the compiler if a 'source'
> is passed whose static type implements java.util.RandomAccess, such as
> java.util.ArrayList. Should you invoke it in a context where the static
> type is 'java.util.List<T>', it will not be picked, and the overload
>
>     public static<T> Stream<T> stream(Collection<T> source);
>
> will be picked instead. This is very likely to happen, which would be a
> shame!
>
> So, I suggest to replace it with the following overload which takes the
> established approach of testing for 'RandomAccess' explicitly:
>
>  public static <T> Stream<T> stream(List<T> source) {
> if(source instanceof RandomAccess) {
>         return new ValuePipeline<>(new
> RandomAccessListStreamAccessor<T,L>(source));
>     }
>
>
>
>
>
>