Proposal: Collection Literals

Kris Nuttycombe kris.nuttycombe at
Tue Mar 31 08:57:03 PDT 2009

On Tue, Mar 31, 2009 at 9:38 AM, Reinier Zwitserloot
<reinier at> wrote:
> Many reasons for not just having varargs constructors on collections
> API classes:
> 1. constructors don't infer generics.
> 2. constructors don't make immutables. Even Arrays.asList doesn't.
> This is how you make an immutable list of constants today:
> Collections.unmodifiableList(Arrays.asList("foo", "bar"));
> that, is, in a word, ridiculous. Even with constructor help, it woud
> become:
> Collections.unmodifiableList(new ArrayList<String>("foo", "bar"));
> not much help, and arguably even worse.

I was imagining something more along the lines of:

Collections.<String>immutableList("foo", "bar"). Of course, this is
currently possible to do as a third-party library, so if one is
content with such syntax there's already a solution.

> It would become, with Joshes proposal:
> ["foo", "bar"]
> which makes me smile.

Yes, however his proposal does not address the issue of simplifying
the construction of mutable collections with initial contents. Of
course, as the original proposal mentions one can always use anonymous
inner classes (Crazybob's contraption) for this.


> 3. import statements. Okay, that's a small one, but nevertheless.
> 4. Implementation is often irrelevant, when the list is immutable
> anyway. Why force people to type ArrayList. For that matter, why force
> people to -read- ArrayList? It's just 'A list with no surprises, which
> is immutable'. That's easy enough to remember.
> 5. varargs are fundamentally broken, though fortunately the proposal
> to address this issue is on the project coin shortlist.
>  --Reinier Zwitserloot

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