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

The

Collectors class is an important part of the StreamAPI. In Java 9, a new method: filtering() was added to the Collectors class. Collectors.filtering()The method can be used to filter elements in the stream. It is similar to the filter() method on a stream. The filter() method processes the values ​​before grouping, while the filtering() method works well with the Collectors.groupingBy() method when filtering Group values ​​before the step occurs.

Syntax

<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>

Example

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);
   }
}

Output

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

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