Java type-system issues:
1. Arrays.asList("foo", "bar") gets the type List<String> when it's the
only thing in the expression, but as soon as you pass it to something else
the type parameter gets inferred to be Object.
2. No way of saying that an Iterator<String> is an Iterator<Object> even
though logically it could be (no covariance or contravariance)
3. Arrays are covariant so the compiler lets you add an invalid item to an
array.
4. List<int> doesn't work. Nothing to do with erasure, as Scala manages it.
5. null inhabits every reference type (like in lots of other mainstream
languages).
6. foreach is not open for extension, i.e., it only works with Iterables
and arrays.
7. try-with-resources is not open for extension, e.g., it can't be made to
work with locks without wrapper objects.
8. Varargs use arrays. Given the incompatibility between generics and
arrays (caused by arrays' covariance) this just seems a mistake. Again,
should be open for extension.
9. No higher kinds. I can't write Monad in Java because there's no way of
saying "this type parameter has a type parameter". This occasionally
results in either code with warnings or duplication.
10. Definite assignment could use a tweak:
final int x;
try {
x = foo();
} catch (FooException e) {
x = 5;
}
That doesn't compile because x might have been assigned to twice. I
suppose that's not really the type system but I've typed out that code on
my phone now so it's staying!
11. A culture issue rather than strictly a type system issue but the whole
Java community seems to have a collective brainfart and start waffling
about complexity budgets when they see Enum<E extends Enum<E>>. Perhaps
the type system issue is that Java has no self types so we end up doing
that in generics.
On Jul 30, 2012 8:17 AM, "Jess Holle" <[email protected]> wrote:
> There are issues.
>
> That said, most developers move on and get a lot done without being overly
> bothered.
>
> A few just seem to get stuck on every wart -- making mountains out of mole
> hills (or warts).
>
> On 7/30/2012 6:11 AM, [email protected] wrote:
>
> > I definitely see a lot of frustration from people over Java's type
> system. Can't say I blame 'em, to be honest.
>
> I'd like to see some numbers here :-) because I don't see any particular
> frustration at all. I'm not saying it's hassle-free, I'm saying is quite
> manageable and there's not frustration.
>
> --
> f.g.
> --
> You received this message because you are subscribed to the Google Groups
> "Java Posse" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected].
> For more options, visit this group at
> http://groups.google.com/group/javaposse?hl=en.
>
>
> --
> You received this message because you are subscribed to the Google Groups
> "Java Posse" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected].
> For more options, visit this group at
> http://groups.google.com/group/javaposse?hl=en.
>
--
You received this message because you are subscribed to the Google Groups "Java
Posse" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/javaposse?hl=en.
