Groups > comp.lang.java.programmer > #38187

Lambda dereference

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From	Daniele Futtorovic <da.futt.news@laposte.net>
Newsgroups	comp.lang.java.programmer
Subject	Lambda dereference
Date	Fri, 16 Mar 2018 19:26:37 +0100
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interface Tagged {
    boolean tag();
}

Stream<Tagged> stream = ...;

You can do this (exhibit A):
   Predicate<Tagged> p = Tagged::tag;
   Collection<Tagged> untagged = stream.filter( p.negate()
).collect(Collectors.toSet());

But you can't do this (exhibit B):
   Collection<Tagged> untagged = stream.filter( (Tagged::tag).negate()
).collect(Collectors.toSet());

Why not? It would be pretty neat. Or am I missing something?

-- 
DF.

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Thread

Lambda dereference Daniele Futtorovic <da.futt.news@laposte.net> - 2018-03-16 19:26 +0100
  Re: Lambda dereference Daniele Futtorovic <da.futt.news@laposte.net> - 2018-03-16 19:32 +0100
    Re: Lambda dereference Andreas Leitgeb <avl@logic.at> - 2018-03-16 23:42 +0000
      Re: Lambda dereference Daniele Futtorovic <da.futt.news@laposte.net> - 2018-03-17 03:10 +0100

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