Comments on: Exploring the syntax in the JDK1.5 early access compiler

By: Neal Gafter

Neal Gafter — Thu, 06 Nov 2003 06:14:26 +0000

> How would sentences would it take to explain List<? extends E> to someone?

How about "A List of some unknown type that is E or some subtype of E"?

Parameterized member functions certainly are allowed, but not often needed.

By: Sune

Sune — Thu, 09 Oct 2003 12:56:11 +0000

Generics makes Java programs a bit harder to read and to understand, that's true. But the improved type safety and reduced number of bugs will make it worth the extra learning effort. Understanding the type system is a requirement for using the language.

If I understand correctly, the extended generics syntax allows you to write member functions like:

class MyClass { public void addThings(List<? extends Thing> list) { ... } }

which would be equivalent to:

class MyClass { public <T extends Thing> void addThings(List<T> list) { ... } }

But are parameterized member (non-static) functions allowed in the current generics proposal?

By: Matt Quail

Matt Quail — Thu, 09 Oct 2003 09:07:14 +0000

Sune, I totally agree that it is powerful to be able to write List<? extends E>. My only concern is its complexity. How would sentences would it take to explain List<? extends E> to someone? What inbuilt type-theory knowledge would they need, beyond the ordinary Java OO principles?

By: Sune

Sune — Thu, 09 Oct 2003 08:56:58 +0000

I like the generics proposal. It’s very powerful to be able to write List, instead of just List. I hope this feature is included in the final release, but I would prefer some other syntax, for example +E.