la forme typée des collections

20:22 Jan 11, 2011 

As you can see, generics is a very different kettle of fish and I believe the French version of the naming convention is much more precise and to the point.

P.S. For what it's worth - over 20 years here as software developer specialising in OO design.

20:18 Jan 11, 2011 

Wow, you've dug up some old question but, since you insist here goes:

The fact that Java confuses generics and types (typing system) is simply its shortcoming. Java model is far from being the best around (see programming languages & OO forums for some lively discussions). In short, the difference is this:

From true generic you can derive (instantiate) various instances with actuals substituted for formals. Substituting types is only one such possibility. You can also substitute things ranging from constants to variables to other generics (nested) to ranges ... whatever your language happens to support.

In the example provided, they defined: 1st - a collection of "anythings" and 2nd - a collection of specifically strings. This is the difference between typed/untyped collections.

A true generic allows you to say that this is a collection of a specific type - but we don't know yet what type it will be.

See the difference?

In one case you have a choice of any type or one specific (specified) type.

In the other, you can say that it will be one type only but, at each instantiation, it may be different. But it must always be the same for every instance.

19:37 Jan 11, 2011 

I'm adding this just in case this thread is referenced in the future. @Kiwiland Bear has posted some comments-- including a potential difference between "typed" vs "generic" in some languages. But in Java, these really are generics. There's really no controversy about that as far as I can see... (Look at the source code posted by @veratek...)

17:06 Oct 29, 2010 

I must admit Java does create some confusion here when it uses typed collections to implement (a very limited form of) generics.

16:52 Oct 29, 2010 

...the difference between generics and types some more. Using some abstract syntax (not to get boggled down by syntax details):

generic some_collection(element_type) - this is generic, meaning we don't know yet what element_type will be.

string_collection = new some_collection(string)
invoice_collection = new some_collection(invoice)
^^^ Those two are non-generic instances. Both are typed (whether or not they are strongly typed depends on the language and is irrelevant as far as generics are concernded).

The original text is obviousl talking about typed vs untyped collections, not generics vs instances.

Cheers!

11:53 Oct 29, 2010 

****List ...<... String... >... nameList = new ArrayList....<... String... >... ();
****nameList.add(“Watson”);

11:51 Oct 29, 2010 

the copy-paste didn't work twice in a row!!

Neil, above is the right "preferred" example - I added the periods, otherwise the String disappears...

11:28 Oct 29, 2010 

See my answer below for what this refers to. Note that very very strictly speaking, there's a difference between Java generics, which are a "weak" form of type checking done at compile time, and "strongly-typed" data, where the *runtime* system imposes type checking. As I say in my answer, you could use "typed" (although I think just talking about the "generic form of collections" is more usual), but I would avoid "strongly typed" as used in the quoted passage in the reference below -- strictly speaking, this usage is not accurate.

(P.S. For what it's worth, I'm a Sun-certified Java programmer with several years' full-time commercial experience.)