Is there any loss in performance instantiating an interface variable as a final class implementing only that interface, as opposed to a class variable?

On Mon, 03 Mar 2014 21:48:16 -0500, Casper Færgemand <shorttail@gmail.com> wrote:

> Is there any loss in performance instantiating an interface variable as a final class implementing only that interface, as opposed to a class variable?

You mean the difference between:

final class C : I {...}

// this
I i = new C;

// and this
C c = new C;

???

The difference in performance is huge. As a final class, no virtual calls are needed. In itself, this is not a huge deal, as a virtual call is not too much worse than a standard call.

However, method calls on the concrete class can be inlined, and an inline call is generally very quick when compared to any kind of other call.

-Steve