What is the importance of Collectors.filtering() method in Java 9?

<strong>public static <T, A, R> Collector<T, ?, R> filtering(Predicate<? super T><!--? super T--> predicate, Collector<? super T, A, R><!--? super T,A,R--> downstream)</strong>

import java.util.stream.*;
import java.util.*;

public class FilteringMethodTest {
   public static void main(String args[]) {
     <strong> List<String></strong> list = <strong>List.of</strong>("x", "yy", "zz", "www");

      <strong>Map<Integer, List<String>></strong> result = list.stream()
                           .<strong>collect</strong>(<strong>Collectors.groupingBy</strong>(String::length,
                            <strong>Collectors.filtering</strong>(s -> !s.contains("<strong>z</strong>"),
                            <strong>Collectors.toList()</strong>)));

      System.out.println(result);
   }
}

<strong>{1=[x], 2=[yy], 3=[www]}</strong>