for (Map.Entry entry: entries){
    result.add(entry.getKey().toString());
}

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.stream.Stream;

public class StreamsTest {

    public static void main(String[] args){
        Map<String, String> mapOfStrings = new HashMap<>();
        mapOfStrings.put("hey1", "hey1Value");
        mapOfStrings.put("hey2", "hey2Value");
        mapOfStrings.put("hey3", "hey3Value");
        mapOfStrings.put("hey4", "hey4Value");

        Set<Map.Entry<String, String>> entries = mapOfStrings.entrySet();
        Stream<Map.Entry<String, String>> stream = entries.stream();
    }

}