Why I cannot cast raw collection elements in stream API?

Asked Apr 22 '20 at 07:32

Active Apr 22 '20 at 07:45

Viewed 58 times

Consider having 2 snippets

List<?> list=...
list.stream().map(Map.class::cast).map(m->m.get("whatever")). ... //compiles and works fine

List rawList=...
rawList.stream().map(Map.class::cast).map(m->m.get("whatever")). ... //does not compile

Second stream casting does not work as map returns Stream while in first example it returns Stream<Map>. Why is that?

edited Apr 22 '20 at 07:38

Gyro Gearless

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asked Apr 22 '20 at 07:32

Antoniossss

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Does any of the answers [here](https://stackoverflow.com/questions/2770321/what-is-a-raw-type-and-why-shouldnt-we-use-it) answer your question? – Sweeper Apr 22 '20 at 07:43
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Essentially, the rule is "once a raw type, forever a raw type" :) – Sweeper Apr 22 '20 at 07:45
Will remember that rule that is for sure, thanks. – Antoniossss Apr 22 '20 at 07:54

Why I cannot cast raw collection elements in stream API?

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