Grouping By alternative (Guava Multimaps)

GroupingByAlternative.java

import com.google.common.collect.ImmutableSetMultimap;
import com.google.common.collect.Multimap;

import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

class GroupingByAlternative {

  public static void main(String... args) {
    var list = List.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);

    Multimap<Boolean, Integer> guava = list.stream()
        .collect(ImmutableSetMultimap.toImmutableSetMultimap(i -> i % 2 == 0, Function.identity()));

    Map<Boolean, List<Integer>> javaCollectors = list.stream()
        .collect(Collectors.groupingBy(i -> i % 2 == 0));

    System.out.println(guava); // {true=[0, 2, 4, 6, 8], false=[1, 3, 5, 7, 9]}
    System.out.println(javaCollectors); // {false=[1, 3, 5, 7, 9], true=[0, 2, 4, 6, 8]}
  }
}