Vector<String>.class vs. Vector.class

[cpjust]

Hi,
I'm trying to pass the class type to a function and I'm getting an error if I try to pass:

Func( Vector<String>.class );

but I only get the unchecked warnings if I change it to:

Func( Vector.class );

How can I pass the proper type Vector<String> to a function?

 

[Diancecht]

I'm not used to generics but I don't think there's a class for a collection.

Anyway, it sounds a bit strange to me. What are you trying to do? Why passing the variable instead of the class is not enough?

Cheers,
Dian

 

[cpjust]

I've had other situations where it would have made my life easier, but today I got bored and started wondering if I could implement C++-style casts instead of the horrible C-style casts that Java uses. This was my first attempt:

public class Cast<D>
{
	public final static <B> D Dynamic( B  base )
	{
		if ( base instanceof D )
		{
			D d = (D)base;
			return d;
		}

		return null;
	}
}

That failed because of several errors which you can easily find out for yourself. So then I came up with my 2nd (but not as intuitive) attempt:

public class Cast
{
	public final static <B, D extends B> D Dynamic( Class<D>  derived,
	                                                	   B  base )
	{
		if ( base.getClass().isAssignableFrom( derived ) == true )
		{
			D d = derived.cast( base );
			return d;
		}

		return null;
	}
}

When I tried testing it by passing it a Vector<String>.class as the first parameter, that's when I noticed Java doesn't like that. :-(

 

[stefanwagner]

Generic information is removed at compile time, it's just visible at compile time.
Therefore passing Vector<String>.class is not possible.

Instead of:

 if (base instanceof D)
{
	D d = (D) base;
	d.foo ();
}
// you could write:
D sampleD = new D ();
D d = Cast.dynamic (sampleD, base);
if (d != null)
{
	d.foo ();
}

I don't see a horrible difference.
If so, than in the second example, where you need an extra sample D, which might often be not that easy to generate.

don't visit my homepage:

http://home.arcor.de/hirnstrom/bewerbung