In Java, I've come across a method that is formatted like this:
public final Subscription subscribe(final Action1<? super T> onNext, final Action1<Throwable> onError) {
}
In the first parameter, what does the question mark and super mean?
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Johann
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2`?` is a generic wildcard ... have you searched for this before posting? – Tim Biegeleisen Aug 21 '16 at 13:53
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1http://stackoverflow.com/questions/4343202/difference-between-super-t-and-extends-t-in-java – Reimeus Aug 21 '16 at 13:57
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... have you seen the StackOverflow **Documentation** on Java? It discusses `? super T` vs. `? extends T` in detail. – Has QUIT--Anony-Mousse Aug 21 '16 at 22:06
1 Answers
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? here means everything that is a superclass of T
super means what you can put into the class (at most this, perhaps a superclass).
Because super indicates the lower bounding class of a generic element. So, Action1<? super T> could represent Action1<T> or Action1<Object>.
Bahramdun Adil
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