Lambda in Stream.map/filter not called

Question

I\'m trying to find separate the duplicates and non-duplicates in a List by adding them to a Set and List while using Stream.fil

Answer 1

There is a more elegant way to use the filter with Predicate negate() method instead of using logical operator !

List extras = strings
.stream()
.filter(((Predicate) distinct::add).negate())
.peek(System.out::println)
.collect(Collectors.toList());

peek is a function used for pipeline debugging only.