Stream.toArray() (original) (raw)

David M. Lloyd david.lloyd at redhat.com
Wed Dec 5 09:28:22 PST 2012

On 12/05/2012 10:43 AM, Remi Forax wrote:

On 12/05/2012 04:44 PM, David M. Lloyd wrote:

Agreed on the array class - another reason is that otherwise folks might expect this to work:

int[] foo = stream.toArray(int[].class); and they will never expect this to work ? int[] foo = stream.toArray(int.class);

No, because the compiler will complain in this case, whereas in the former case, the failure will happen at runtime. Though to be fair, in the latter case the compiler would still accept this incorrect input:

Integer[] foo = stream.toArray(int.class);

I've used an array class because this is what you want an instance of an array class, so I've tried: public <A extends Object[]> A asArray(Class clazz); to reject toArray(int[]) but for a reason that I don't understand you can not use Object[] as bound.

Rémi

On 12/05/2012 09:39 AM, Brian Goetz wrote: Agree on the general form -- toArray(clazz) is definitely better than the current bad alternatives offered by Collection.

I prefer that the argument be the component class, not the array class. I think toArray(Foo.class) is far more natural to users than toArray(Foo[].class). On 12/5/2012 10:33 AM, Remi Forax wrote: Restarting a thread that ends without clear winner.

Currently, Stream.toArray() is specified as: Object[] toArray() which is not what users want, given the lack of reified generics and the fact that it's usually hard for a user to predict the number of elements of a Stream, the best signature seems to be: A[] toArray(Class arrayClass) with arrayClass.isArray() returning true and arrayClass.getComponentType().isPrimitive() returning false (or if you prefer Object[].class.isAssignableFrom(arrayClass) returning true) example of usage, Person[] coolPersons = persons.stream().filter(person#isCool()).toArray(Person[].class); cheers, Rémi

--

More information about the lambda-libs-spec-experts mailing list