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Comment by yarg | Hacker News Reader

Looking at the head of a List does not work. The class of that element is within the scope of <? extends ListType>, an is not necessarily not ListType.

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To spell this out so it's a bit more obvious, given a Thing at head of a list, you could have:

    - a List<Thing>
    - a List<ThingSuperclass>
    - a List<? extends Thing>
    - a List<? super ThingSubclass>
    - a List<IThing>
    - a List<ILiterallyAnyImplementedIFace>
    - a List<IHaventForgottenInterfacesCanExtendOthers>
    - a List<Object>
    - a List<I'm probably forgetting some possibilities>

And you have no way of knowing which it is.

So yes, it's a boundary, which is significantly more than nothing. But far less useful than it feels like at first.

*and is not necessarily ListType.

Idiot.

For the downvoters, the author is correcting themselves after the edit window. It's clearly self-deprecating humor, not a personal attack.

Not to mention that an empty list still has a type...

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