Re: Re[2]: [Haskell-cafe] Re: What I wish someone had told me...

On Thu, 2008-10-16 at 10:02 -0700, Robert Greayer wrote:

--- On Thu, 10/16/08, Jonathan Cast wrote:

...

Can I have HashSet<Integer>? Could I construct HashSet, if I did?

Yes:

HashSet<?> blah = (HashSet<?>) hashSetClass.newInstance();

... compiles, and won't throw an exception if hashSetClass truly is the class object for HashSet.

But I can't say new HashSet()?

Pretty useless, because you can't put anything *into* a HashSet object...

Even if my client hands my a ? object?

blah.add("foo"); // doesn't typecheck...

but you can do: HashSet<String> blah = (HashSet<String>) hashSetClass.newInstance(); blah.add("foo");

works fine..

jcc