On Mon, 30 Jul 2012 14:55:30 +0200, Ricky Clarkson
<[email protected]> wrote:
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.
Ok, I call this minor.
2. No way of saying that an Iterator<String> is an Iterator<Object> even
though logically it could be (no covariance or contravariance)
This is a major pain, but I still have to see an explanation that shows
that covariance in generics doesn't open a serious hole in type safety.
3. Arrays are covariant so the compiler lets you add an invalid item to
an
array.
Ditto.
4. List<int> doesn't work. Nothing to do with erasure, as Scala manages
it.
Agreed, this is major. But now please tell me how Scala does it :-).
5. null inhabits every reference type (like in lots of other mainstream
languages).
This is complex to debate. In any case, I wouldn't expect anything
different from an industrial, general purpose language from the '90s.
6. foreach is not open for extension, i.e., it only works with Iterables
and arrays.
I call this minor.
7. try-with-resources is not open for extension, e.g., it can't be made
to
work with locks without wrapper objects.
try-with-resources is completely useless. Lombok's @Cleanup is at least as
robust and more flexible.
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.
Medium level.
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.
I call this minor, unless somebody shows me how Monads would make my life
so much better.
--
Fabrizio Giudici - Java Architect, Project Manager
Tidalwave s.a.s. - "We make Java work. Everywhere."
[email protected]
http://tidalwave.it - http://fabriziogiudici.it
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