Because they aren't the same.
Here you go:
legal:
List<Employee> emps = new ArrayList<>();
emps = new LinkedList<>();
will fail, because LInkedList is not an ArrayList:
var emps = new ArrayList<Employee>();
emps = new LinkedList<Employee>();
This, and the problem of introducing a new keyword, were major reasons
for NOT going the var route. Furthermore, what diamond does already
exists in java so its only a very minor update: unlike constructors,
static methods _do_ infer, it's like they have implicit diamond
operators:
this is legal today if you use guava:
List<Employee> emps = Lists.newArrayList();
Now you know the thinking of the powers that be on the coin mailing
list. There's a nuance I've been arguing for on coin-dev back during
the time proposals were considered, which was two-fold:
1. There's no need for even diamond; just get rid of the idea of raw
for -source 1.7, and let that become 'infer it please'. It might even
be possible to remain backwards compatible.
2. While 'var' has all sorts of issues, both practical (new keyword is
a problem, and not being able to assign a LinkedList to an ArrayList
var is confusing), and ideological ("List" and "ArrayList" in List x =
new ArrayList() convey different meanings; they should not be mixed
up), these issues go away when we look at only FINAL variables.
There's no problem with confusion about assigning a LinkedList to
something initialized as an ArrayList. The ideological argument loses
a lot of its momentum when you realize that any kind of chaining on
expressions does not even allow you to list a more general type.
"final" itself can serve as the keyword, solving the last problem.
Thus, while this:
var list = new ArrayList<String>();
wouldn't be legal, this should have been:
final list = new ArrayList<String>();
unfortunately this idea was not accepted.
On Sep 22, 5:21 pm, Serge Boulay <serge.bou...@gmail.com> wrote:
> Is there some particular reason Oracle choose the diamond operator over
> something like “var” ?
>
> For example, I find this
>
> List<Employee> emps = new ArrayList<>();
>
> far less intuitive than say
>
> var emps = new ArrayList<Employee>();
>
> The second example has the added benefit that it would work with all types.
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