Collect stream with grouping, counting and filtering operations

Question

I\'m trying to collect stream throwing away rarely used items like in this example:

import java.util.*;
import java.util.function.Function;
import static java.ut         


        

Answer 1

I personally prefer Holger's solution (+1), but, instead of removing elements from the groupingBy map, I would filter its entrySet and map the result to a Set in the finalizer (it feels even more streamy to me)

    Set commonlyUsed = allWords.stream().collect(
            collectingAndThen(
                groupingBy(identity(), counting()), 
                (map) -> map.entrySet().stream().
                            filter(e -> e.getValue() > 2).
                            map(e -> e.getKey()).
                            collect(Collectors.toSet())));