stream api: partition by

package ch.claude_martin;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;

public class SomeClass {
    public static void main(String[] args) {
        HashMap<Integer, String> map = new HashMap<>();
        map.put(1, "foo");
        map.put(2, "bar");
        map.put(3, "qux");
        map.put(4, "grault");
        map.put(5, "garply");
        map.put(6, "thud");
        map.put(7, "flob");
        System.out.println(map);
        // {1=foo, 2=bar, 3=qux, 4=grault, 5=garply, 6=thud, 7=flob}

        Map<Boolean, Map<Integer, String>> part = map.entrySet().stream().collect(//
                Collectors.partitioningBy(e -> e.getValue().contains("a"),
                        Collectors.toMap(e -> e.getKey(), e -> e.getValue())));

        Map<Integer, String> containsA = part.get(true);
        Map<Integer, String> rest = part.get(false);

        System.out.println(containsA); // {2=bar, 4=grault, 5=garply}
        System.out.println(rest); // {1=foo, 3=qux, 6=thud, 7=flob}
    }
}