import java.util.HashMap;
import java.util.stream.Collectors;

public class JI9029015 {

	public static void main(String[] args) {
		HashMap<String, String> m = new HashMap<>(); 
		m.put("A", "a"); 
		m.put("B", "b"); 
		m.put("C", "c"); 
		m.entrySet().parallelStream().collect(Collectors.toMap(e -> e.getKey(), e -> e.getValue())); 

		m.put("D", null); 
		m.entrySet().parallelStream().collect(Collectors.toMap(e -> e.getKey(), e -> e.getValue())); 

	}

}