Re: looping through a list, starting at 1
Andreas Leitgeb wrote:
Lew wrote:
Andreas Leitgeb wrote:
Lew wrote:
Andreas Leitgeb wrote:
Lew wrote:
Volker Borchert wrote:
if (l instanceof RandomAccess) {
Tests on type like this are an antipattern.
Are marker-interfaces (which RandomAccess is, iirc) already an
antipattern, or is there a different way to check for them, [...]
With generics you can use type intersections so that something has to be
both 'List' and 'RandomAccess' (again, say) even to reach the call or the
class or whatever.
Interesting stuff! (but still falls a bit short):
public static <T extends List,RandomAccess> T method(T raAcList) {
// public static <T extends List> T method(T anyList) {
You cannot have two erasure-equivalent methods in the same class, ...
It isn't obvious to me, how these really *need* to be erasure-equivalent.
I mean, obviously they are, but that's just a fact of Java as it is,
not a principial necessity.
If Java had a consistent model of intersection types even outside
of generics, like "List & RandomAccess raList = new ArrayList();",
then the erased type of first method()'s "T" would be just that
intersection type, and the methods would be obviously erasure-
*un*equivalent.
No need to tell me it ain't so. I know. :-(
Alas.
The generics trick is suitable when you want to insist
that the argument be of the particular type, not when
you want to bifurcate as you indicated.
But bifurcation was the context of this discussion about
"instanceof"-red flags!
And my point was that there often is a way to put that bifurcation into a compile-time structure rather than run time. Doing 'instanceof' is a red flag that the type analysis is incomplete and there may be a compile-time way to do it instead.
It seems as though perhaps you are in a situation where you
want to fork on the type at run-time, ...
Well, not me. See Volker's posting up-thread for the context
in which he suggested use of "instanceof".
The generic "you".
Forking on "implementing or not implementing a particular
marker-interface" is an entirely different situation from
asserting a particular interface/type. I'm all with you
that the latter be done at compile-time whenever even
remotely possible.
Now, would you call "instanceof" in the specific context of
bifurcation (with none of the branches just barfing) still
a red flag?
Yes.
--
Lew