RFC: draft API for JEP 269 Convenience Collection Factories

Stephen Colebourne scolebourne at joda.org
Fri Oct 9 13:11:47 UTC 2015

On 9 October 2015 at 00:39, Stuart Marks <stuart.marks at oracle.com> wrote:
> 1. Number of fixed arg overloads.

Guava follows this pattern:

of(T, T)
of(T, T, T)
of(T, T, T, T... elements)

whereas the proposal has

of(T, T)
of(T, T, T)
of(T... elements)

I'd be interested to know why Guava did it that way and what the trade offs are.

> 2. Other concrete collection factories.
> I've chosen to provide factories for the concrete collections ArrayList,
> HashSet, and HashMap, since those seem to be the most commonly used. Is
> there a need to provide factories for other concrete collections, such as
> LinkedHashMap?

LinkedHashMap definitely
LinkedList definitely not (as its very slow and use should not be encouraged).
TreeSet/TreeMap, maybe, they'd need an extra parameter though.

> 3. Duplicate handling.
> My current thinking is for the Set and Map factories to throw
> IllegalArgumentException if a duplicate element or key is detected.


Given that ofEntries() takes a Map.Entry as input, why does
Map.KeyValueHolder need to be public? This would require
Map.entry(K,V) return Map.Entry, not Map.KeyValueHolder.


More information about the core-libs-dev mailing list